Start <- function(..., # dim = indices/selectors, 
                       # dim_var = 'var', 
                       # dim_reorder = Sort/CircularSort, 
                       # dim_tolerance = number, 
                       # dim_depends = 'file_dim', 
                       # dim_across = 'file_dim', 
                  return_vars = NULL, 
                  synonims = NULL, 
                  file_opener = NcOpener, 
                  file_var_reader = NcVarReader, 
                  file_dim_reader = NcDimReader, 
                  file_data_reader = NcDataReader, 
                  file_closer = NcCloser, 
                  transform = NULL, 
                  transform_params = NULL, 
                  transform_vars = NULL, 
                  transform_extra_cells = 0, 
                  apply_indices_after_transform = FALSE, 
                  pattern_dims = NULL,
                  metadata_dims = NULL, 
                  selector_checker = SelectorChecker, 
                  num_procs = NULL, silent = FALSE, debug = FALSE) {
                  #, config_file = NULL
                  #dictionary_dim_names = ,
                  #dictionary_var_names =  
  dim_params <- list(...)

  # Take *_var parameters apart
  var_params_ind <- grep('_var$', names(dim_params))
  var_params <- dim_params[var_params_ind]
  # Check all *_var are NULL or vectors of character strings, and 
  # that they all have a matching dimension param.
  i <- 1
  for (var_param in var_params) {
    if (!is.character(var_param)) {
      stop("All '*_var' parameters must be character strings.")
    } else if (!any(grepl(paste0('^', strsplit(names(var_params)[i], 
                                               '_var$')[[1]][1], '$'),
                          names(dim_params)))) {
      stop(paste0("All '*_var' parameters must be associated to a dimension parameter. Found parameter '", 
                  names(var_params)[i], "' but no parameter '", 
                  strsplit(names(var_params)[i], '_var$')[[1]][1], "'."))
    }
    i <- i + 1
  }
  # Make the keys of 'var_params' to be the name of 
  # the corresponding dimension.
  if (length(var_params) < 1) {
    var_params <- NULL
  } else {
    names(var_params) <- gsub('_var$', '', names(var_params))
  }

  # Take *_reorder parameters apart
  dim_reorder_params_ind <- grep('_reorder$', names(dim_params))
  dim_reorder_params <- dim_params[dim_reorder_params_ind]
  # Check all *_reorder are NULL or functions, and that they all have 
  # a matching dimension param.
  i <- 1
  for (dim_reorder_param in dim_reorder_params) {
    if (!is.function(dim_reorder_param)) {
      stop("All '*_reorder' parameters must be functions.")
    } else if (!any(grepl(paste0('^', strsplit(names(dim_reorder_params)[i], 
                                               '_reorder$')[[1]][1], '$'),
                          names(dim_params)))) {
      stop(paste0("All '*_reorder' parameters must be associated to a dimension parameter. Found parameter '", 
                  names(dim_reorder_params)[i], "' but no parameter '", 
                  strsplit(names(dim_reorder_params)[i], '_reorder$')[[1]][1], "'."))
    } else if (!any(grepl(paste0('^', strsplit(names(dim_reorder_params)[i], 
                                               '_reorder$')[[1]][1], '$'),
                          names(var_params)))) {
      stop(paste0("All '*_reorder' parameters must be associated to a dimension parameter associated to a ",
                  "variable. Found parameter '", names(dim_reorder_params)[i], "' and dimension parameter '", 
                  strsplit(names(dim_reorder_params)[i], '_reorder$')[[1]][1], "' but did not find variable ",
                  "parameter '", strsplit(names(dim_reorder_params)[i], '_reorder$')[[1]][1], "_var'."))
    }
    i <- i + 1
  }
  # Make the keys of 'dim_reorder_params' to be the name of 
  # the corresponding dimension.
  if (length(dim_reorder_params) < 1) {
    dim_reorder_params <- NULL
  } else {
    names(dim_reorder_params) <- gsub('_reorder$', '', names(dim_reorder_params))
  }

  # Take *_tolerance parameters apart
  tolerance_params_ind <- grep('_tolerance$', names(dim_params))
  tolerance_params <- dim_params[tolerance_params_ind]
  # Check all *_tolerance are NULL or vectors of character strings, and 
  # that they all have a matching dimension param.
  i <- 1
  for (tolerance_param in tolerance_params) {
    if (!any(grepl(paste0('^', strsplit(names(tolerance_params)[i], 
                                               '_tolerance$')[[1]][1], '$'),
                          names(dim_params)))) {
      stop(paste0("All '*_tolerance' parameters must be associated to a dimension parameter. Found parameter '", 
                  names(tolerance_params)[i], "' but no parameter '", 
                  strsplit(names(tolerance_params)[i], '_tolerance$')[[1]][1], "'."))
    } else if (!any(grepl(paste0('^', strsplit(names(tolerance_params)[i], 
                                               '_tolerance$')[[1]][1], '$'),
                          names(var_params)))) {
      stop(paste0("All '*_tolerance' parameters must be associated to a dimension parameter associated to a ",
                  "variable. Found parameter '", names(tolerance_params)[i], "' and dimension parameter '", 
                  strsplit(names(tolerance_params)[i], '_tolerance$')[[1]][1], "' but did not find variable ",
                  "parameter '", strsplit(names(tolerance_params)[i], '_tolerance$')[[1]][1], "_var'."))
    }
    i <- i + 1
  }
  # Make the keys of 'tolerance_params' to be the name of 
  # the corresponding dimension.
  if (length(tolerance_params) < 1) {
    tolerance_params <- NULL
  } else {
    names(tolerance_params) <- gsub('_tolerance$', '', names(tolerance_params))
  }

  # Take *_depends parameters apart
  depends_params_ind <- grep('_depends$', names(dim_params))
  depends_params <- dim_params[depends_params_ind]
  # Check all *_depends are NULL or vectors of character strings, and 
  # that they all have a matching dimension param.
  i <- 1
  for (depends_param in depends_params) {
    if (!is.character(depends_param) || (length(depends_param) > 1)) {
      stop("All '*_depends' parameters must be single character strings.")
    } else if (!any(grepl(paste0('^', strsplit(names(depends_params)[i], 
                                               '_depends$')[[1]][1], '$'),
                          names(dim_params)))) {
      stop(paste0("All '*_depends' parameters must be associated to a dimension parameter. Found parameter '", 
                  names(depends_params)[i], "' but no parameter '", 
                  strsplit(names(depends_params)[i], '_depends$')[[1]][1], "'."))
    }
    i <- i + 1
  }
  # Make the keys of 'depends_params' to be the name of 
  # the corresponding dimension.
  if (length(depends_params) < 1) {
    depends_params <- NULL
  } else {
    names(depends_params) <- gsub('_depends$', '', names(depends_params))
  }
  # Change name to depending_file_dims
  depending_file_dims <- depends_params

  # Take *_across parameters apart
  across_params_ind <- grep('_across$', names(dim_params))
  across_params <- dim_params[across_params_ind]
  # Check all *_across are NULL or vectors of character strings, and 
  # that they all have a matching dimension param.
  i <- 1
  for (across_param in across_params) {
    if (!is.character(across_param) || (length(across_param) > 1)) {
      stop("All '*_across' parameters must be single character strings.")
    } else if (!any(grepl(paste0('^', strsplit(names(across_params)[i], 
                                               '_across$')[[1]][1], '$'),
                          names(dim_params)))) {
      stop(paste0("All '*_across' parameters must be associated to a dimension parameter. Found parameter '", 
                  names(across_params)[i], "' but no parameter '", 
                  strsplit(names(across_params)[i], '_across$')[[1]][1], "'."))
    }
    i <- i + 1
  }
  # Make the keys of 'across_params' to be the name of 
  # the corresponding dimension.
  if (length(across_params) < 1) {
    across_params <- NULL
  } else {
    names(across_params) <- gsub('_across$', '', names(across_params))
  }
  # Change name to inner_dims_across_files
  inner_dims_across_files <- across_params

  # Leave alone the dimension parameters in the variable dim_params
  if (length(c(var_params_ind, dim_reorder_params_ind, tolerance_params_ind,
               depends_params_ind, across_params_ind)) > 0) {
    dim_params <- dim_params[-c(var_params_ind, dim_reorder_params_ind,
                                tolerance_params_ind, depends_params_ind,
                                across_params_ind)]
  }
  dim_names <- names(dim_params)
  if (is.null(dim_names)) {
    stop("At least one pattern dim must be specified.")
  }

  # Check pattern_dims
  if (is.null(pattern_dims)) {
    .warning(paste0("Parameter 'pattern_dims' not specified. Taking the first dimension, '", 
                    dim_names[1], "' as 'pattern_dims'."))
    pattern_dims <- dim_names[1]
  } else if (is.character(pattern_dims) && (length(pattern_dims) > 0)) {
    pattern_dims <- unique(pattern_dims)
  } else {
    stop("Parameter 'pattern_dims' must be a vector of character strings.")
  }
  if (any(names(var_params) %in% pattern_dims)) {
    stop("'*_var' parameters specified for pattern dimensions. Remove or fix them.")
  }
  # Find the pattern dimension with the pattern specifications
  found_pattern_dim <- NULL
  for (pattern_dim in pattern_dims) {
    # Check all specifications in pattern_dim are valid
    dat <- datasets <- dim_params[[pattern_dim]]
    if (is.null(dat) || !(is.character(dat) && all(nchar(dat) > 0)) && !is.list(dat)) {
      stop(paste0("Parameter '", pattern_dim, 
                  "' must be a list of lists with pattern specifications or a vector of character strings."))
    }
    if (!is.null(dim_reorder_params[[pattern_dim]])) {
      .warning(paste0("A reorder for the selectors of '", pattern_dim, 
                      "' has been specified, but it is a pattern dimension and the reorder will be ignored."))
    }
    if (any(sapply(dat, is.list))) {
      if (is.null(found_pattern_dim)) {
        found_pattern_dim <- pattern_dim
      } else {
        stop("Found more than one pattern dim with pattern specifications (list of lists). One and only one pattern dim must contain pattern specifications.")
      }
    }
  }
  if (is.null(found_pattern_dim)) {
    .warning(paste0("Taking the first pattern dim, '", pattern_dims[1], "', as dimension with pattern specifications (to be fetched in configuration file)."))
    found_pattern_dim <- pattern_dims[1]
  }

  # Check metadata_dims
  if (!is.null(metadata_dims)) {
    if (!is.character(metadata_dims) || (length(metadata_dims) < 1)) {
      stop("Parameter 'metadata' dims must be a vector of at least one character string.")
    }
  } else {
    metadata_dims <- pattern_dims
  }

  # Once the pattern dimension with dataset specifications is found,
  # the variable 'dat' is mounted with the information of each
  # dataset.
  dat <- datasets <- dim_params[[found_pattern_dim]]
  dat_info_names <- c('name', 'path')#, 'nc_var_name', 'suffix', 'var_min', 'var_max', 'dimnames')
  dat_to_fetch <- c()
  dat_names <- c()
  if (!is.list(dat)) {
    dat <- as.list(dat)
  }
  for (i in 1:length(dat)) {
    if (is.character(dat[[i]]) && length(dat[[i]]) == 1 && nchar(dat[[i]]) > 0) {
      if (grepl('^(\\./|\\.\\./|/.*/|~/)', dat[[i]])) {
        dat[[i]] <- list(path = dat[[i]])
      } else {
        dat[[i]] <- list(name = dat[[i]])
      }
    } else if (!is.list(dat[[i]])) {
      stop(paste0("Parameter '", pattern_dim, 
                  "' is incorrect. It must be a list of lists or character strings."))
    }
    #if (!(all(names(dat[[i]]) %in% dat_info_names))) {
    #  stop("Error: parameter 'dat' is incorrect. There are unrecognized components in the information of some of the datasets. Check 'dat' in ?Load for details.")
    #}
    if (!('name' %in% names(dat[[i]]))) {
      dat[[i]][['name']] <- paste0('dat', i)
      if (!('path' %in% names(dat[[i]]))) {
        stop(paste0("Parameter '", found_pattern_dim, 
                    "' is incorrect. A 'path' should be provided for each dataset if no 'name' is provided."))
      }
    } else if (!('path' %in% names(dat[[i]]))) {
      dat_to_fetch <- c(dat_to_fetch, i)
    }
    #if ('path' %in% names(dat[[i]])) {
    #  if (!('nc_var_name' %in% names(dat[[i]]))) {
    #    dat[[i]][['nc_var_name']] <- '$var_name$'
    #  }
    #  if (!('suffix' %in% names(dat[[i]]))) {
    #    dat[[i]][['suffix']] <- ''
    #  }
    #  if (!('var_min' %in% names(dat[[i]]))) {
    #    dat[[i]][['var_min']] <- ''
    #  }
    #  if (!('var_max' %in% names(dat[[i]]))) {
    #    dat[[i]][['var_max']] <- ''
    #  }
    #}
    dat_names <- c(dat_names, dat[[i]][['name']])
  }
  if ((length(dat_to_fetch) > 0) && (length(dat_to_fetch) < length(dat))) {
    .warning("'path' has been provided for some datasets. Any information in the configuration file related to these will be ignored.")
  }

  # Reorder inner_dims_across_files (to make the keys be the file dimensions,
  # and the values to be the inner dimensions that go across it).
  if (!is.null(inner_dims_across_files)) {
    # Reorder: example, convert list(ftime = 'chunk', ensemble = 'member', xx = 'chunk')
    #                        to list(chunk = c('ftime', 'xx'), member = 'ensemble')
    new_idaf <- list()
    for (i in names(inner_dims_across_files)) {
      if (!(inner_dims_across_files[[i]] %in% names(new_idaf))) {
        new_idaf[[inner_dims_across_files[[i]]]] <- i
      } else {
        new_idaf[[inner_dims_across_files[[i]]]] <- c(new_idaf[[inner_dims_across_files[[i]]]], i)
      }
    }
    inner_dims_across_files <- new_idaf
  }

  # Check return_vars
  if (is.null(return_vars)) {
    return_vars <- list()
#    if (length(var_params) > 0) {
#      return_vars <- as.list(paste0(names(var_params), '_var'))
#    } else {
#      return_vars <- list()
#    }
  }
  if (!is.list(return_vars)) {
    stop("Parameter 'return_vars' must be a list or NULL.")
  }
  if (length(return_vars) > 0 && is.null(names(return_vars))) {
#    names(return_vars) <- rep('', length(return_vars))
    stop("Parameter 'return_vars' must be a named list.")
  }
  i <- 1
  while (i <= length(return_vars)) {
#    if (names(return_vars)[i] == '') {
#      if (!(is.character(return_vars[[i]]) && (length(return_vars[[i]]) == 1))) {
#        stop("The ", i, "th specification in 'return_vars' is malformed.")
#      } 
#      if (!grepl('_var$', return_vars[[i]])) {
#        stop("The ", i, "th specification in 'return_vars' is malformed.")
#      }
#      dim_name <- strsplit(return_vars[[i]], '_var$')[[1]][1]
#      if (!(dim_name %in% names(var_params))) {
#        stop("'", dim_name, "_var' requested in 'return_vars' but ",
#             "no '", dim_name, "_var' specified in the .Load call.")
#      }
#      names(return_vars)[i] <- var_params[[dim_name]]
#      return_vars[[i]] <- found_pattern_dim
#    } else
    if (length(return_vars[[i]]) > 0) { 
      if (!is.character(return_vars[[i]])) {
        stop("The ", i, "th specification in 'return_vars' is malformed. It ",
             "must be a vector of character strings of valid file dimension ",
             "names.")
      }
    }
    i <- i + 1
  }

  # Check synonims
  if (!is.null(synonims)) {
    error <- FALSE
    if (!is.list(synonims)) {
      error <- TRUE
    }
    for (synonim_entry in names(synonims)) {
      if (!(synonim_entry %in% names(dim_params)) &&
          !(synonim_entry %in% names(return_vars))) {
        error <- TRUE
      }
      if (!is.character(synonims[[synonim_entry]]) ||
          length(synonims[[synonim_entry]]) < 1) {
        error <- TRUE
      }
    }
    if (error) {
      stop("Parameter 'synonims' must be a named list, where the names are ",
           "a name of a requested dimension or variable and the values are ",
           "vectors of character strings with at least one alternative name ",
           " for each dimension or variable in 'synonims'.")
    }
  }
  if (length(unique(names(synonims))) < length(names(synonims))) {
    stop("There must not be repeated entries in 'synonims'.")
  }
  if (length(unique(unlist(synonims))) < length(unlist(synonims))) {
    stop("There must not be repeated values in 'synonims'.")
  }
  # Make that all dims and vars have an entry in synonims, even if only dim_name = dim_name
  dim_entries_to_add <- which(!(names(dim_params) %in% names(synonims)))
  if (length(dim_entries_to_add) > 0) {
    synonims[names(dim_params)[dim_entries_to_add]] <- as.list(names(dim_params)[dim_entries_to_add])
  }
  var_entries_to_add <- which(!(names(var_params) %in% names(synonims)))
  if (length(var_entries_to_add) > 0) {
    synonims[names(var_params)[var_entries_to_add]] <- as.list(names(var_params)[var_entries_to_add])
  }

  # Check selector_checker
  if (is.null(selector_checker) || !is.function(selector_checker)) {
    stop("Parameter 'selector_checker' must be a function.")
  }

  # Check file_opener
  if (is.null(file_opener) || !is.function(file_opener)) {
    stop("Parameter 'file_opener' must be a function.")
  }

  # Check file_var_reader
  if (!is.null(file_var_reader) && !is.function(file_var_reader)) {
    stop("Parameter 'file_var_reader' must be a function.")
  }

  # Check file_dim_reader
  if (!is.null(file_dim_reader) && !is.function(file_dim_reader)) {
    stop("Parameter 'file_dim_reader' must be a function.")
  }

  # Check file_data_reader
  if (is.null(file_data_reader) || !is.function(file_data_reader)) {
    stop("Parameter 'file_data_reader' must be a function.")
  }

  # Check file_closer
  if (is.null(file_closer) || !is.function(file_closer)) {
    stop("Parameter 'file_closer' must be a function.")
  }

  # Check transform
  if (!is.null(transform)) {
    if (!is.function(transform)) {
      stop("Parameter 'transform' must be a function.")
    }
  }

  # Check transform_params
  if (!is.null(transform_params)) {
    if (!is.list(transform_params)) {
      stop("Parameter 'transform_params' must be a list.")
    }
    if (is.null(names(transform_params))) {
      stop("Parameter 'transform_params' must be a named list.")
    }
  }

  # Check transform_vars
  if (!is.null(transform_vars)) {
    if (!is.character(transform_vars)) {
      stop("Parameter 'transform_vars' must be a vector of character strings.")
    }
  }
  if (any(!(transform_vars %in% names(return_vars)))) {
    stop("All the variables specified in 'transform_vars' must also be specified in 'return_vars'.")
  }

  # Check apply_indices_after_transform
  if (!is.logical(apply_indices_after_transform)) {
    stop("Parameter 'apply_indices_after_transform' must be either TRUE or FALSE.")
  }
  aiat <- apply_indices_after_transform

  # Check transform_extra_cells
  if (!is.numeric(transform_extra_cells)) {
    stop("Parameter 'transform_extra_cells' must be numeric.")
  }
  transform_extra_cells <- round(transform_extra_cells)

  # Check num_procs
  if (!is.null(num_procs)) {
    if (!is.numeric(num_procs)) {
      stop("Parameter 'num_procs' must be numeric.")
    } else {
      num_procs <- round(num_procs)
    }
  }

  # Check silent
  if (!is.logical(silent)) {
    stop("Parameter 'silent' must be logical.")
  }

  dim_params[[found_pattern_dim]] <- dat_names

  if (!silent) {
    .message(paste0("Exploring files... This will take a variable amount ",
                    "of time depending on the issued request and the ",
                    "performance of the file server..."))
  }

if (!is.character(debug)) {
dims_to_check <- c('time')
} else {
dims_to_check <- debug
debug <- TRUE
}

  ############################## READING FILE DIMS ############################
  # Check that no unrecognized variables are present in the path patterns
  # and also that no file dimensions are requested to THREDDs catalogs.
  # And in the mean time, build all the work pieces and look for the 
  # first available file of each dataset.
  array_of_files_to_load <- NULL
  array_of_not_found_files <- NULL
  indices_of_first_files_with_data <- vector('list', length(dat))
  selectors_of_first_files_with_data <- vector('list', length(dat))
  found_file_dims <- vector('list', length(dat))
  expected_inner_dims <- vector('list', length(dat))
  dataset_has_files <- rep(FALSE, length(dat))
#print("A")
  for (i in 1:length(dat)) {
#print("B")
    dat_selectors <- dim_params
    dat_selectors[[found_pattern_dim]] <- dat_selectors[[found_pattern_dim]][i]
    dim_vars <- paste0('$', dim_names, '$')
    file_dims <- dim_names[which(sapply(dim_vars, grepl, dat[[i]][['path']], fixed = TRUE))]
    file_dims <- unique(c(pattern_dims, file_dims))
    found_file_dims[[i]] <- file_dims
    expected_inner_dims[[i]] <- dim_names[which(!(dim_names %in% file_dims))]
    # (Check the depending_file_dims).
    if (any(c(names(depending_file_dims), unlist(depending_file_dims)) %in% 
            expected_inner_dims[[i]])) {
      stop(paste0("The dimension dependancies specified in ",
                  "'depending_file_dims' can only be between file ",
                  "dimensions, but some inner dimensions found in ",
                  "dependancies for '", dat[[i]][['name']], "', which ",
                  "has the following file dimensions: ", 
                  paste(paste0("'", file_dims, "'"), collapse = ', '), ".")) 
    } else {
      a <- names(depending_file_dims) %in% file_dims
      b <- unlist(depending_file_dims) %in% file_dims
      ab <- a & b
      if (any(!ab)) {
        .warning("Detected some dependancies in 'depending_file_dims' with ",
                 "non-existing dimension names. These will be disregarded.")
        depending_file_dims <- depending_file_dims[-which(!ab)]
      }
      if (any(names(depending_file_dims) == unlist(depending_file_dims))) {
        depending_file_dims <- depending_file_dims[-which(names(depending_file_dims) == unlist(depending_file_dims))]
      }
    }
    # (Check the inner_dims_across_files).
    if (any(!(names(inner_dims_across_files) %in% file_dims)) ||
        any(!(unlist(inner_dims_across_files) %in% expected_inner_dims[[i]]))) {
      stop(paste0("All relationships specified in ",
                  "'inner_dims_across_files' must be between a inner ",
                  "dimension and a file dimension. Found wrong ",
                  "specification for '", dat[[i]][['name']], "', which ",
                  "has the following file dimensions: ", 
                  paste(paste0("'", file_dims, "'"), collapse = ', '),
                  ", and the following inner dimensions: ", 
                  paste(paste0("'", expected_inner_dims[[i]], "'"), 
                        collapse = ', '), "."))
    }
    # (Check the return_vars).
    j <- 1
    while (j <= length(return_vars)) {
      if (any(!(return_vars[[j]] %in% file_dims))) {
        if (any(return_vars[[j]] %in% expected_inner_dims[[i]])) {
          stop("Found variables in 'return_vars' requested ",
               "for some inner dimensions (for dataset '",
               dat[[i]][['name']], "'), but variables can only be ",
               "requested for file dimensions.")
        } else {
          stop("Found variables in 'return_vars' requested ",
               "for non-existing dimensions.")
        }
      }
      j <- j + 1
    }
    # (Check the metadata_dims).
    if (any(!(metadata_dims %in% file_dims))) {
      stop("All dimensions in 'metadata_dims' must be file dimensions.")
    }
    # (Check the *_var parameters).
    if (any(!(unlist(var_params) %in% names(return_vars)))) {
      stop("All '*_var' params must associate a dimension to one of the ",
           "requested variables in 'return_vars'.")
    }
#    # (Check the circular_dims parameters). 
#    if (!all(names(circular_dims) %in% expected_inner_dims[[i]])) {
#      stop("Only inner dimensions can be requested as 'circular_dims'.")
#    }
    replace_values <- vector('list', length = length(file_dims))
    names(replace_values) <- file_dims
    # Take the first selector for all possible file dimensions
    for (file_dim in file_dims) {
      if (file_dim %in% names(var_params)) {
        .warning(paste0("The '", file_dim, "_var' param will be ignored since '", 
                        file_dim, "' is a file dimension (for the dataset with pattern ", 
                        dat[[i]][['path']], ")."))
      }
      if (!is.list(dat_selectors[[file_dim]]) || 
          (is.list(dat_selectors[[file_dim]]) && 
           length(dat_selectors[[file_dim]]) == 2 &&
           is.null(names(dat_selectors[[file_dim]])))) {
        dat_selectors[[file_dim]] <- list(dat_selectors[[file_dim]])
      }
      first_class <- class(dat_selectors[[file_dim]][[1]])
      first_length <- length(dat_selectors[[file_dim]][[1]])
      for (j in 1:length(dat_selectors[[file_dim]])) {
        sv <- selector_vector <- dat_selectors[[file_dim]][[j]]
        if (!identical(first_class, class(sv)) ||
            !identical(first_length, length(sv))) {
          stop("All provided selectors for depending dimensions must ",
               "be vectors of the same length and of the same class.")
        }
        if (is.character(sv) && !((length(sv) == 1) && (sv[1] %in% c('all', 'first', 'last')))) {
          dat_selectors[[file_dim]][[j]] <- selector_checker(selectors = sv,
                                                             return_indices = FALSE)
        } else if (!(is.numeric(sv) || 
                     (is.character(sv) && (length(sv) == 1) && (sv %in% c('all', 'first', 'last'))) || 
                     (is.list(sv) && (length(sv) == 2) && (all(sapply(sv, is.character)) || 
                                                           all(sapply(sv, is.numeric)))))) {
          stop("All explicitly provided selectors for file dimensions must be character strings.")
        } 
      }
      sv <- dat_selectors[[file_dim]][[1]]
      if (is.character(sv) && !((length(sv) == 1) && (sv[1] %in% c('all', 'first', 'last')))) {
        replace_values[[file_dim]] <- dat_selectors[[file_dim]][[1]][1]
      }
    }
#print("C")
    # Now we know which dimensions whose selectors are provided non-explicitly.
    undefined_file_dims <- file_dims[which(sapply(replace_values, is.null))]
    defined_file_dims <- file_dims[which(!(file_dims %in% undefined_file_dims))]
    # Quickly check if the depending dimensions are provided properly.
    for (file_dim in file_dims) {
      if (file_dim %in% names(depending_file_dims)) {
        ## TODO: Detect multi-dependancies and forbid.
        if (all(c(file_dim, depending_file_dims[[file_dim]]) %in% defined_file_dims)) {
          if (length(dat_selectors[[file_dim]]) != length(dat_selectors[[depending_file_dims[[file_dim]]]][[1]])) {
            stop(paste0("If providing selectors for the depending ",
                        "dimension '", file_dim, "', a ",
                        "vector of selectors must be provided for ",
                        "each selector of the dimension it depends on, '",
                        depending_file_dims[[file_dim]], "'."))
          } else if (!all(names(dat_selectors[[file_dim]]) == dat_selectors[[depending_file_dims[[file_dim]]]][[1]])) {
            stop(paste0("If providing selectors for the depending ",
                        "dimension '", file_dim, "', the name of the ",
                        "provided vectors of selectors must match ",
                        "exactly the selectors of the dimension it ",
                        "depends on, '", depending_file_dims[[file_dim]], "'."))
          }
        }
      }
    }
    # Find the possible values for the selectors that are provided as
    # indices. If the requested file is on server, impossible operation.
    if (length(grep("^http", dat[[i]][['path']])) > 0) {
      if (length(undefined_file_dims) > 0) {
        stop(paste0("All selectors for the file dimensions must be ",
                    "character strings if requesting data to a remote ",
                    "server. Found invalid selectors for the file dimensions ",
                    paste(paste0("'", undefined_file_dims, "'"), collapse = ', '), "."))
      }
      dataset_has_files[i] <- TRUE
    } else {
      dat[[i]][['path']] <- path.expand(dat[[i]][['path']])
      # Iterate over the known dimensions to find the first existing file.
      # The path to the first existing file will be used to find the 
      # values for the non explicitly defined selectors.
      first_file <- NULL
      first_file_selectors <- NULL
      if (length(undefined_file_dims) > 0) {
        replace_values[undefined_file_dims] <- '*'
      }
      ## TODO: What if length of defined_file_dims is 0? code might crash (in practice it worked for an example case)
      files_to_check <- sapply(dat_selectors[defined_file_dims], function(x) length(x[[1]]))
      sub_array_of_files_to_check <- array(1:prod(files_to_check), dim = files_to_check)
      j <- 1
#print("D")
      while (j <= prod(files_to_check) && is.null(first_file)) {
        selector_indices <- which(sub_array_of_files_to_check == j, arr.ind = TRUE)[1, ]
        selectors <- sapply(1:length(defined_file_dims), 
          function (x) {
            vector_to_pick <- 1
            if (defined_file_dims[x] %in% names(depending_file_dims)) {
              vector_to_pick <- selector_indices[which(defined_file_dims == depending_file_dims[[defined_file_dims[x]]])]
            }
            dat_selectors[defined_file_dims][[x]][[vector_to_pick]][selector_indices[x]]
          })
        replace_values[defined_file_dims] <- selectors
        file_path <- .ReplaceVariablesInString(dat[[i]][['path']], replace_values)
        file_path <- Sys.glob(file_path)
        if (length(file_path) > 0) {
          first_file <- file_path[1]
          first_file_selectors <- selectors
        }
        j <- j + 1
      }
#print("E")
      # Start looking for values for the non-explicitly defined selectors.
      if (is.null(first_file)) {
        .warning(paste0("No found files for the datset '", dat[[i]][['name']], 
                        "'. Provide existing selectors for the file dimensions ",
                        " or check and correct its path pattern: ", dat[[i]][['path']]))
      } else {
        dataset_has_files[i] <- TRUE
        ## TODO: Improve message here if no variable found:
        if (length(undefined_file_dims) > 0) {
          # Looking for the first values, parsed from first_file.
          first_values <- vector('list', length = length(undefined_file_dims))
          names(first_values) <- undefined_file_dims
          found_values <- 0
          stop <- FALSE
          try_dim <- 1
          last_success <- 1
          while ((found_values < length(undefined_file_dims)) && !stop) {
            u_file_dim <- undefined_file_dims[try_dim]
            if (is.null(first_values[[u_file_dim]])) {
              path_with_globs_and_tag <- .ReplaceVariablesInString(dat[[i]][['path']], 
                                           replace_values[-which(file_dims == u_file_dim)],
                                           allow_undefined_key_vars = TRUE)
              found_value <- .FindTagValue(path_with_globs_and_tag, 
                                           first_file, u_file_dim)
              if (!is.null(found_value)) {
                found_values <- found_values + 1
                last_success <- try_dim
                first_values[[u_file_dim]] <- found_value
                replace_values[[u_file_dim]] <- found_value
              }
            }
            try_dim <- (try_dim %% length(undefined_file_dims)) + 1
            if (try_dim == last_success) {
              stop <- TRUE
            }
          }
          if (found_values < length(undefined_file_dims)) {
            stop(paste0("Path pattern of dataset '", dat[[i]][['name']], 
                        "' is too complex. Could not automatically ",
                        "detect values for all non-explicitly defined ",
                        "indices. Check its pattern: ", dat[[i]][['path']]))
          }
          ## TODO: Replace ReplaceGlobExpressions by looped call to FindTagValue? As done above
          ##       Maybe it can solve more cases actually. I got warnings in ReplGlobExp with a typical
          ##       cmor case, requesting all members and chunks for fixed var and sdate. Not fixing
          ##       sdate raised 'too complex' error.
          # Replace shell globs in path pattern and keep the file_dims as tags
          dat[[i]][['path']] <- .ReplaceGlobExpressions(dat[[i]][['path']], first_file, replace_values, 
                                                        file_dims, dat[[i]][['name']], FALSE)
          # Now time to look for the available values for the non 
          # explicitly defined selectors for the file dimensions.
#print("H")
          # Check first the ones that do not depend on others.
          ufd <- c(undefined_file_dims[which(!(undefined_file_dims %in% names(depending_file_dims)))],
                   undefined_file_dims[which(undefined_file_dims %in% names(depending_file_dims))])
                  
          for (u_file_dim in ufd) {
            replace_values[undefined_file_dims] <- first_values
            replace_values[[u_file_dim]] <- '*'
            depended_dim <- NULL
            depended_dim_values <- NA
            selectors <- dat_selectors[[u_file_dim]][[1]]
            if (u_file_dim %in% names(depending_file_dims)) {
              depended_dim <- depending_file_dims[[u_file_dim]]
              depended_dim_values <- dat_selectors[[depended_dim]][[1]]
              dat_selectors[[u_file_dim]] <- vector('list', length = length(depended_dim_values))
              names(dat_selectors[[u_file_dim]]) <- depended_dim_values
            } else {
              dat_selectors[[u_file_dim]] <- list()
            }
            if (u_file_dim %in% unlist(depending_file_dims)) {
              depending_dims <- names(depending_file_dims)[which(sapply(depending_file_dims, function(x) u_file_dim %in% x))]
              replace_values[depending_dims] <- rep('*', length(depending_dims))
            }
            for (j in 1:length(depended_dim_values)) {
              parsed_values <- c()
              if (!is.null(depended_dim)) {
                replace_values[[depended_dim]] <- depended_dim_values[j]
              }
              path_with_globs <- .ReplaceVariablesInString(dat[[i]][['path']], replace_values)
              found_files <- Sys.glob(path_with_globs)
              ## TODO: Enhance this error message, or change by warning.
              ##       Raises if a wrong sdate is specified, for example.
              if (length(found_files) == 0) {
                .warning(paste0("Could not find files for any '", u_file_dim, 
                                "' for '", depended_dim, "' = '", 
                                depended_dim_values[j], "'."))
                dat_selectors[[u_file_dim]][[j]] <- NA
              } else {
                for (found_file in found_files) {
                  path_with_globs_and_tag <- .ReplaceVariablesInString(dat[[i]][['path']],
                                               replace_values[-which(file_dims == u_file_dim)],
                                               allow_undefined_key_vars = TRUE)
                  parsed_values <- c(parsed_values, 
                                     .FindTagValue(path_with_globs_and_tag, found_file, 
                                                   u_file_dim))
                }
                dat_selectors[[u_file_dim]][[j]] <- selector_checker(selectors = selectors,
                                                                     var = unique(parsed_values),
                                                                     return_indices = FALSE)
              }
            }
          }
#print("I")
        } else {
          dat[[i]][['path']] <- .ReplaceGlobExpressions(dat[[i]][['path']], first_file, replace_values, 
                                                        defined_file_dims, dat[[i]][['name']], FALSE)
        }
      }
    }
    # Now fetch for the first available file
    if (dataset_has_files[i]) {
      known_dims <- file_dims
    } else {
      known_dims <- defined_file_dims
    }
    replace_values <- vector('list', length = length(known_dims))
    names(replace_values) <- known_dims
    files_to_load <- sapply(dat_selectors[known_dims], function(x) length(x[[1]]))
    files_to_load[found_pattern_dim] <- 1
    sub_array_of_files_to_load <- array(1:prod(files_to_load), 
                                        dim = files_to_load)
    names(dim(sub_array_of_files_to_load)) <- known_dims
    sub_array_of_not_found_files <- array(!dataset_has_files[i], 
                                          dim = files_to_load)
    names(dim(sub_array_of_not_found_files)) <- known_dims
    j <- 1
    while (j <= prod(files_to_load)) {
      selector_indices <- which(sub_array_of_files_to_load == j, arr.ind = TRUE)[1, ]
      names(selector_indices) <- known_dims
      selectors <- sapply(1:length(known_dims), 
        function (x) {
          vector_to_pick <- 1
          if (known_dims[x] %in% names(depending_file_dims)) {
            vector_to_pick <- selector_indices[which(known_dims == depending_file_dims[[known_dims[x]]])]
          }
          dat_selectors[known_dims][[x]][[vector_to_pick]][selector_indices[x]]
        })
      names(selectors) <- known_dims
      replace_values[known_dims] <- selectors
      if (!dataset_has_files[i]) {
        if (any(is.na(selectors))) {
          replace_values <- replace_values[-which(names(replace_values) %in% names(selectors[which(is.na(selectors))]))]
        }
        file_path <- .ReplaceVariablesInString(dat[[i]][['path']], replace_values, TRUE)
        sub_array_of_files_to_load[j] <- file_path        
      } else {
        if (any(is.na(selectors))) {
          replace_values <- replace_values[-which(names(replace_values) %in% names(selectors[which(is.na(selectors))]))]
          file_path <- .ReplaceVariablesInString(dat[[i]][['path']], replace_values, TRUE)
          sub_array_of_files_to_load[j] <- file_path
          sub_array_of_not_found_files[j] <- TRUE
        } else {
          file_path <- .ReplaceVariablesInString(dat[[i]][['path']], replace_values)
          sub_array_of_files_to_load[j] <- file_path
          if (is.null(indices_of_first_files_with_data[[i]])) {
            if (!(length(grep("^http", file_path)) > 0)) {
              if (!file.exists(file_path)) {
                file_path <- NULL
              }
            }
            if (!is.null(file_path)) {
              test_file <- NULL
              ## TODO: suppress error messages
              test_file <- file_opener(file_path)
              if (!is.null(test_file)) {
                selector_indices[which(known_dims == found_pattern_dim)] <- i
                indices_of_first_files_with_data[[i]] <- selector_indices
                selectors_of_first_files_with_data[[i]] <- selectors
                file_closer(test_file)
              }
            }
          }
        }
      }
      j <- j + 1
    }
    # Extend array as needed progressively
    if (is.null(array_of_files_to_load)) {
        array_of_files_to_load <- sub_array_of_files_to_load
        array_of_not_found_files <- sub_array_of_not_found_files
    } else {
      array_of_files_to_load <- .MergeArrays(array_of_files_to_load, sub_array_of_files_to_load,
                                             along = found_pattern_dim)
      ## TODO: file_dims, and variables like that.. are still ok now? I don't think so
      array_of_not_found_files <- .MergeArrays(array_of_not_found_files, sub_array_of_not_found_files,
                                               along = found_pattern_dim)
    }    
    dat[[i]][['selectors']] <- dat_selectors
  }
  if (all(sapply(indices_of_first_files_with_data, is.null))) {
    stop("No data files found for any of the specified datasets.")
  }

  ########################### READING INNER DIMS. #############################
#print("J")
  ## TODO: To be run in parallel (local multi-core)
  # Now time to work out the inner file dimensions.
  # First pick the requested variables.
  dims_to_iterate <- NULL
  for (return_var in names(return_vars)) {
    dims_to_iterate <- unique(c(dims_to_iterate, return_vars[[return_var]]))
  }
  if (found_pattern_dim %in% dims_to_iterate) {
    dims_to_iterate <- dims_to_iterate[-which(dims_to_iterate == found_pattern_dim)]
  }
  common_return_vars <- NULL
  common_first_found_file <- NULL
  common_return_vars_pos <- NULL
  if (length(return_vars) > 0) {
    common_return_vars_pos <- which(sapply(return_vars, function(x) !(found_pattern_dim %in% x)))
  }
  if (length(common_return_vars_pos) > 0) {
    common_return_vars <- return_vars[common_return_vars_pos]
    return_vars <- return_vars[-common_return_vars_pos]
    common_first_found_file <- rep(FALSE, length(which(sapply(common_return_vars, length) == 0)))
    names(common_first_found_file) <- names(common_return_vars[which(sapply(common_return_vars, length) == 0)])
  }
  return_vars <- lapply(return_vars, 
    function(x) {
      if (found_pattern_dim %in% x) {
        x[-which(x == found_pattern_dim)]
      } else {
        x
      }
    })
  if (length(common_return_vars) > 0) {
    picked_common_vars <- vector('list', length = length(common_return_vars))
    names(picked_common_vars) <- names(common_return_vars)
  } else {
    picked_common_vars <- NULL
  }
  picked_common_vars_ordered <- picked_common_vars
  picked_common_vars_unorder_indices <- picked_common_vars
  picked_vars <- vector('list', length = length(dat))
  names(picked_vars) <- dat_names
  picked_vars_ordered <- picked_vars
  picked_vars_unorder_indices <- picked_vars
  for (i in 1:length(dat)) {
    if (dataset_has_files[i]) {
      # Put all selectors in a list of a single list/vector of selectors. 
      # The dimensions that go across files will later be extended to have 
      # lists of lists/vectors of selectors.
      for (inner_dim in expected_inner_dims[[i]]) {
        if (!is.list(dat[[i]][['selectors']][[inner_dim]]) || 
            (is.list(dat[[i]][['selectors']][[inner_dim]]) && 
             length(dat[[i]][['selectors']][[inner_dim]]) == 2 &&
             is.null(names(dat[[i]][['selectors']][[inner_dim]])))) {
          dat[[i]][['selectors']][[inner_dim]] <- list(dat[[i]][['selectors']][[inner_dim]])
        }
      }
      if (length(return_vars) > 0) {
        picked_vars[[i]] <- vector('list', length = length(return_vars))
        names(picked_vars[[i]]) <- names(return_vars)
        picked_vars_ordered[[i]] <- picked_vars[[i]]
        picked_vars_unorder_indices[[i]] <- picked_vars[[i]]
      }
      indices_of_first_file <- as.list(indices_of_first_files_with_data[[i]])
      array_file_dims <- sapply(dat[[i]][['selectors']][found_file_dims[[i]]], function(x) length(x[[1]]))
      names(array_file_dims) <- found_file_dims[[i]]
      if (length(dims_to_iterate) > 0) {
        indices_of_first_file[dims_to_iterate] <- lapply(array_file_dims[dims_to_iterate], function(x) 1:x)
      }
      array_of_var_files <- do.call('[', c(list(x = array_of_files_to_load), indices_of_first_file, list(drop = FALSE)))
      array_of_var_indices <- array(1:length(array_of_var_files), dim = dim(array_of_var_files))
      array_of_not_found_var_files <- do.call('[', c(list(x = array_of_not_found_files), indices_of_first_file, list(drop = FALSE)))
      previous_indices <- rep(-1, length(indices_of_first_file))
      names(previous_indices) <- names(indices_of_first_file)
      first_found_file <- NULL
      if (length(return_vars) > 0) {
        first_found_file <- rep(FALSE, length(which(sapply(return_vars, length) == 0)))
        names(first_found_file) <- names(return_vars[which(sapply(return_vars, length) == 0)])
      }
      for (j in 1:length(array_of_var_files)) {
        current_indices <- which(array_of_var_indices == j, arr.ind = TRUE)[1, ]
        names(current_indices) <- names(indices_of_first_file)
        if (!is.na(array_of_var_files[j]) && !array_of_not_found_var_files[j]) {
          changed_dims <- which(current_indices != previous_indices)
          vars_to_read <- NULL
          if (length(return_vars) > 0) {
            vars_to_read <- names(return_vars)[sapply(return_vars, function(x) any(names(changed_dims) %in% x))]
          }
          if (!is.null(first_found_file)) {
            if (any(!first_found_file)) {
              vars_to_read <- c(vars_to_read, names(first_found_file[which(!first_found_file)]))
            }
          }
          if ((i == 1) && (length(common_return_vars) > 0)) {
            vars_to_read <- c(vars_to_read, names(common_return_vars)[sapply(common_return_vars, function(x) any(names(changed_dims) %in% x))])
          }
          if (!is.null(common_first_found_file)) {
            if (any(!common_first_found_file)) {
              vars_to_read <- c(vars_to_read, names(common_first_found_file[which(!common_first_found_file)]))
            }
          }
          file_object <- file_opener(array_of_var_files[j])
          if (is.null(file_object)) {
            stop("Unexpected error. Could not find the file ", array_of_var_files[j])
          }
          for (var_to_read in vars_to_read) {
            if (var_to_read %in% unlist(var_params)) {
              associated_dim_name <- names(var_params)[which(unlist(var_params) == var_to_read)]
            }
            var_name_to_reader <- var_to_read
            names(var_name_to_reader) <- 'var'
            var_dims <- file_dim_reader(NULL, file_object, var_name_to_reader, NULL,
                                        synonims)
            # file_dim_reader returns dimension names as found in the file.
            # Need to translate accoridng to synonims:
            names(var_dims) <- sapply(names(var_dims), 
              function(x) {
                which_entry <- which(sapply(synonims, function(y) x %in% y))
                if (length(which_entry) > 0) {
                  names(synonims)[which_entry]
                } else {
                  x
                }
              })
            if (!is.null(var_dims)) {
              var_file_dims <- NULL
              if (var_to_read %in% names(common_return_vars)) {
                var_to_check <- common_return_vars[[var_to_read]]
              } else {
                var_to_check <- return_vars[[var_to_read]]
              }
              if (any(names(dim(array_of_files_to_load)) %in% var_to_check)) {
                var_file_dims <- dim(array_of_files_to_load)[which(names(dim(array_of_files_to_load)) %in% 
                                                                   var_to_check)]
              }
              if (((var_to_read %in% names(common_return_vars)) && 
                   is.null(picked_common_vars[[var_to_read]])) ||
                  ((var_to_read %in% names(return_vars)) && 
                   is.null(picked_vars[[i]][[var_to_read]]))) {
                if (any(names(var_file_dims) %in% names(var_dims))) {
                  stop("Found a requested var in 'return_var' requested for a ",
                       "file dimension which also appears in the dimensions of ",
                       "the variable inside the file.\n", array_of_var_files[j])
                }
                special_types <- list('POSIXct' = as.POSIXct, 'POSIXlt' = as.POSIXlt, 
                                      'Date' = as.Date)
                first_sample <- file_var_reader(NULL, file_object, NULL, 
                                                var_to_read, synonims)
                if (any(class(first_sample) %in% names(special_types))) {
                  array_size <- prod(c(var_file_dims, var_dims))
                  new_array <- rep(special_types[[class(first_sample)[1]]](NA), array_size)
                  dim(new_array) <- c(var_file_dims, var_dims)
                } else {
                  new_array <- array(dim = c(var_file_dims, var_dims))
                }
                attr(new_array, 'variables') <- attr(first_sample, 'variables')
                if (var_to_read %in% names(common_return_vars)) {
                  picked_common_vars[[var_to_read]] <- new_array
                  pick_ordered <- FALSE 
                  if (var_to_read %in% unlist(var_params)) {
                    if (associated_dim_name %in% names(dim_reorder_param) && !aiat) {
                      picked_common_vars_ordered[[var_to_read]] <- new_array
                      pick_ordered <- TRUE
                    }
                  }
                  if (!pick_ordered) {
                    picked_common_vars_ordered[[var_to_read]] <- NULL
                  }
                } else {
                  picked_vars[[i]][[var_to_read]] <- new_array
                  pick_ordered <- FALSE
                  if (var_to_read %in% unlist(var_params)) {
                    if (associated_dim_name %in% names(dim_reorder_params) && !aiat) {
                      picked_vars_ordered[[i]][[var_to_read]] <- new_array
                      pick_ordered <- TRUE
                    }
                  }
                  if (!pick_ordered) {
                    picked_vars_ordered[[i]][[var_to_read]] <- NULL
                  }
                }
              } else {
                if (var_to_read %in% names(common_return_vars)) {
                  array_var_dims <- dim(picked_common_vars[[var_to_read]])
                } else {
                  array_var_dims <- dim(picked_vars[[i]][[var_to_read]])
                }
                if (any(names(array_var_dims) %in% names(var_file_dims))) {
                  array_var_dims <- array_var_dims[-which(names(array_var_dims) %in% names(var_file_dims))]
                }
                if (names(array_var_dims) != names(var_dims)) {
                  stop("Error while reading the variable '", var_to_read, "' from ",
                       "the file. Dimensions do not match.\nExpected ", 
                       paste(paste0("'", names(array_var_dims), "'"), 
                             collapse = ', '), " but found ",
                       paste(paste0("'", names(var_dims), "'"), 
                             collapse = ', '), ".\n", array_of_var_files[j])
                }
                if (any(var_dims > array_var_dims)) {
                  stop("Error while reading the variable '", var_to_read, "' from ",
                       "the file. Found size (", paste(var_dims, collapse = ' x '), 
                       ") is greater than expected maximum size (", 
                       array_var_dims, ").")
                }
              }
              var_store_indices <- c(as.list(current_indices[names(var_file_dims)]), lapply(var_dims, function(x) 1:x))
              var_values <- file_var_reader(NULL, file_object, NULL, var_to_read, synonims)
              if (var_to_read %in% unlist(var_params)) {
                if ((associated_dim_name %in% names(dim_reorder_params)) && !aiat) {
                  ## Is this check really needed?
                  if (length(dim(var_values)) > 1) {
                    stop("Requested a '", associated_dim_name, "_reorder' for a dimension ",
                         "whose coordinate variable that has more than 1 dimension. This is ",
                         "not supported.")
                  }
                  ordered_var_values <- dim_reorder_params[[associated_dim_name]](var_values)
                  if (!all(c('x', 'ix') %in% names(ordered_var_values))) {
                    stop("All the dimension reorder functions must return a list with the components 'x' and 'ix'.")
                  }
                  # Save the indices to reorder back the ordered variable values.
                  # This will be used to define the first round indices.
                  unorder <- sort(ordered_var_values$ix, index.return = TRUE)$ix
                  if (var_to_read %in% names(common_return_vars)) {
                     picked_common_vars_ordered[[var_to_read]] <- do.call('[<-', 
                       c(list(x = picked_common_vars_ordered[[var_to_read]]), 
                         var_store_indices, 
                         list(value = ordered_var_values$x)))
                     picked_common_vars_unorder_indices[[var_to_read]] <- do.call('[<-', 
                       c(list(x = picked_common_vars_unorder_indices[[var_to_read]]), 
                         var_store_indices, 
                         list(value = unorder)))
                  } else {
                     picked_vars_ordered[[i]][[var_to_read]] <- do.call('[<-', 
                       c(list(x = picked_vars_ordered[[i]][[var_to_read]]), 
                         var_store_indices, 
                         list(value = ordered_var_values$x)))
                     picked_vars_unorder_indices[[i]][[var_to_read]] <- do.call('[<-', 
                       c(list(x = picked_vars_unorder_indices[[i]][[var_to_read]]), 
                         var_store_indices, 
                         list(value = unorder)))
                  }
                }
              }
              if (var_to_read %in% names(common_return_vars)) {
                 picked_common_vars[[var_to_read]] <- do.call('[<-', 
                   c(list(x = picked_common_vars[[var_to_read]]), 
                     var_store_indices, 
                     list(value = var_values)))
              } else {
                 picked_vars[[i]][[var_to_read]] <- do.call('[<-', 
                   c(list(x = picked_vars[[i]][[var_to_read]]), 
                     var_store_indices, 
                     list(value = var_values)))
              }
              if (var_to_read %in% names(first_found_file)) {
                first_found_file[var_to_read] <- TRUE
              }
              if (var_to_read %in% names(common_first_found_file)) {
                common_first_found_file[var_to_read] <- TRUE
              }
            } else {
              stop("Could not find variable '", var_to_read, 
                   "' in the file ", array_of_var_files[j])
            }
          }
          file_closer(file_object)
        }
        previous_indices <- current_indices
      }
    }
  }
  # Once we have the variable values, we can work out the indices
  # for the implicitly defined selectors.
  #
  # Trnasforms a vector of indices v expressed in a world of 
  # length N from 1 to N, into a world of length M, from
  # 1 to M. Repeated adjacent indices are collapsed.
  transform_indices <- function(v, n, m) { 
    #unique2 turns e.g. 1 1 2 2 2 3 3 1 1 1 into 1 2 3 1
    unique2 <- function(v) {
      if (length(v) < 2) {
        v
      } else {
        v[c(1, v[2:length(v)] - v[1:(length(v) - 1)]) != 0]
      }
    }
    unique2(round(((v - 1) / (n - 1)) * (m - 1))) + 1 # this rounding may generate 0s. what then?
  }
  beta <- transform_extra_cells
  dims_to_crop <- vector('list')
  transformed_vars <- vector('list', length = length(dat))
  names(transformed_vars) <- dat_names
  transformed_vars_ordered <- transformed_vars
  transformed_vars_unorder_indices <- transformed_vars
  transformed_common_vars <- NULL
  transformed_common_vars_ordered <- NULL
  transformed_common_vars_unorder_indices <- NULL

  for (i in 1:length(dat)) {
    if (dataset_has_files[i]) {
      indices <- indices_of_first_files_with_data[[i]]
      if (!is.null(indices)) {
        file_path <- do.call("[", c(list(array_of_files_to_load), as.list(indices_of_first_files_with_data[[i]])))
        # The following 5 lines should go several lines below, but were moved
        # here for better performance.
        # If any of the dimensions comes without defining variable, then we read
        # the data dimensions.
        data_dims <- NULL
        if (length(unlist(var_params[expected_inner_dims[[i]]])) < length(expected_inner_dims[[i]])) {
          file_to_open <- file_path
          data_dims <- file_dim_reader(file_to_open, NULL, selectors_of_first_files_with_data[[i]],
                                       lapply(dat[[i]][['selectors']][expected_inner_dims[[i]]], '[[', 1),
                                       synonims)
          # file_dim_reader returns dimension names as found in the file.
          # Need to translate accoridng to synonims:
          names(data_dims) <- sapply(names(data_dims),
            function(x) {
              which_entry <- which(sapply(synonims, function(y) x %in% y))
              if (length(which_entry) > 0) {
                names(synonims)[which_entry]
              } else {
                x
              }
            })
        }
        # Transform the variables if needed and keep them apart.
        if (!is.null(transform) && (length(transform_vars) > 0)) {
          if (!all(transform_vars %in% c(names(picked_vars[[i]]), names(picked_common_vars)))) {
            stop("Could not find all the required variables in 'transform_vars' ",
                 "for the dataset '", dat[[i]][['name']], "'.")
          }
          vars_to_transform <- NULL
          picked_vars_to_transform <- which(names(picked_vars[[i]]) %in% transform_vars)
          if (length(picked_vars_to_transform) > 0) {
            picked_vars_to_transform <- names(picked_vars[[i]])[picked_vars_to_transform]
            new_vars_to_transform <- picked_vars[[i]][picked_vars_to_transform]
            which_are_ordered <- which(!sapply(picked_vars_ordered[[i]][picked_vars_to_transform], is.null))
            if (length(which_are_ordered) > 0) {
              new_vars_to_transform[which_are_ordered] <- picked_vars_ordered[[i]][which_are_ordered]
            }
            vars_to_transform <- c(vars_to_transform, new_vars_to_transform)
          }
          picked_common_vars_to_transform <- which(names(picked_common_vars) %in% transform_vars)
          if (length(picked_common_vars_to_transform) > 0) {
            picked_common_vars_to_transform <- names(picked_common_vars)[picked_common_vars_to_transform]
            new_vars_to_transform <- picked_common_vars[[i]][picked_common_vars_to_transform]
            which_are_ordered <- which(!sapply(picked_common_vars_ordered[[i]][picked_common_vars_to_transform], is.null))
            if (length(which_are_ordered) > 0) {
              new_vars_to_transform[which_are_ordered] <- picked_common_vars_ordered[[i]][which_are_ordered]
            }
            vars_to_transform <- c(vars_to_transform, new_vars_to_transform)
          }
          # Transform the variables
          transformed_data <- do.call(transform, c(list(data_array = NULL,
                                                        variables = vars_to_transform,
                                                        file_dims = found_file_dims[[i]]),
                                                   transform_params))
          # Discard the common transformed variables if already transformed before
          if (!is.null(transformed_common_vars)) {
            common_ones <- which(names(picked_common_vars) %in% names(transformed_data$variables))
            if (length(common_ones) > 0) {
              transformed_data$variables <- transformed_data$variables[-common_ones]
            }
          }
          transformed_vars[[i]] <- list()
          transformed_vars_ordered[[i]] <- list()
          transformed_vars_unorder_indices[[i]] <- list()
          # Order the transformed variables if needed
          # 'var_to_read' should be 'transformed_var', but is kept to reuse the same code as above.
          for (var_to_read in names(transformed_data$variables)) {
            if (var_to_read %in% unlist(var_params)) {
              associated_dim_name <- names(var_params)[which(unlist(var_params) == var_to_read)]
              if ((associated_dim_name %in% names(dim_reorder_params)) && aiat) {
                ## Is this check really needed?
                if (length(dim(transformed_data$variables[[associated_dim_name]])) > 1) {
                  stop("Requested a '", associated_dim_name, "_reorder' for a dimension ",
                       "whose coordinate variable that has more than 1 dimension (after ",
                       "transform). This is not supported.")
                }
                ordered_var_values <- dim_reorder_params[[associated_dim_name]](transformed_data$variables[[associated_dim_name]])
                if (!all(c('x', 'ix') %in% names(ordered_var_values))) {
                  stop("All the dimension reorder functions must return a list with the components 'x' and 'ix'.")
                }
                # Save the indices to reorder back the ordered variable values.
                # This will be used to define the first round indices.
                unorder <- sort(ordered_var_values$ix, index.return = TRUE)$ix
                if (var_to_read %in% names(picked_common_vars)) {
                  transformed_common_vars_ordered[[var_to_read]] <- ordered_var_values$x
                  transformed_common_vars_unorder_indices[[var_to_read]] <- unorder
                } else {
                  transformed_vars_ordered[[i]][[var_to_read]] <- ordered_var_values$x
                  transformed_vars_unorder_indices[[i]][[var_to_read]] <- unorder
                }
              }
            }
          }
          transformed_picked_vars <- which(names(picked_vars[[i]]) %in% names(transformed_data$variables))
          if (length(transformed_picked_vars) > 0) {
            transformed_picked_vars <- names(picked_vars[[i]])[transformed_picked_vars]
            transformed_vars[[i]][transformed_picked_vars] <- transformed_data$variables[transformed_picked_vars]
          }
          if (is.null(transformed_common_vars)) {
            transformed_picked_common_vars <- which(names(picked_common_vars) %in% names(transformed_data$variables))
            if (length(transformed_picked_common_vars) > 0) {
              transformed_picked_common_vars <- names(picked_common_vars)[transformed_picked_common_vars]
              transformed_common_vars <- transformed_data$variables[transformed_picked_common_vars]
            }
          }
        }
        # Once the variables are transformed, we compute the indices to be 
        # taken for each inner dimension.
        # In all cases, indices will have to be computed to know which data
        # values to take from the original data for each dimension (if a 
        # variable is specified for that dimension, it will be used to 
        # convert the provided selectors into indices). These indices are
        # referred to as 'first round of indices'.
        # The taken data will then be transformed if needed, together with
        # the dimension variable if specified, and, in that case, indices 
        # will have to be computed again to know which values to take from the 
        # transformed data. These are the 'second round of indices'. In the 
        # case there is no transformation, the second round of indices will
        # be all the available indices, i.e. from 1 to the number of taken
        # values with the first round of indices.
        for (inner_dim in expected_inner_dims[[i]]) {
if (debug) {
print("-> DEFINING INDICES FOR INNER DIMENSION:")
print(inner_dim)
}
          selector_array <- dat[[i]][['selectors']][[inner_dim]][[1]]
if (debug) {
if (inner_dim %in% dims_to_check) {
print(paste0("-> DEBUG MESSAGES FOR THE DATASET", i, " AND INNER DIMENSION '", inner_dim, "':"))
print("-> STRUCTURE OF SELECTOR ARRAY:")
print(str(selector_array))
print("-> PICKED VARS:")
print(picked_vars)
print("-> TRANSFORMED VARS:")
print(transformed_vars)
}
}
          if (is.null(dim(selector_array))) {
            dim(selector_array) <- length(selector_array)
          }
          if (is.null(names(dim(selector_array)))) {
            if (length(dim(selector_array)) == 1) {
              names(dim(selector_array)) <- inner_dim
            } else {
              stop("Provided selector arrays must be provided with dimension ",
                   "names. Found an array of selectors without dimension names ",
                   "for the dimension '", inner_dim, "'.")
            } 
          }
          selectors_are_indices <- FALSE
          if (!is.null(attr(selector_array, 'indices'))) {
            if (!is.logical(attr(selector_array, 'indices'))) {
              stop("The atribute 'indices' for the selectors for the dimension '", 
                   inner_dim, "' must be TRUE or FALSE.")
            }
            selectors_are_indices <- attr(selector_array, 'indices')
          }
          file_dim <- NULL
          if (inner_dim %in% unlist(inner_dims_across_files)) {
            file_dim <- names(inner_dims_across_files)[which(sapply(inner_dims_across_files, function(x) inner_dim %in% x))[1]]
            chunk_amount <- length(dat[[i]][['selectors']][[file_dim]][[1]])
            names(chunk_amount) <- file_dim
          } else {
            chunk_amount <- 1
          }
          taken_chunks <- rep(FALSE, chunk_amount)
          selector_file_dims <- 1
          if (any(found_file_dims[[i]] %in% names(dim(selector_array)))) {
            selector_file_dims <- dim(selector_array)[which(names(dim(selector_array)) %in% found_file_dims[[i]])]
          }
          selector_inner_dims <- dim(selector_array)[which(!(names(dim(selector_array)) %in% found_file_dims[[i]]))]
          var_with_selectors <- NULL
          var_with_selectors_name <- var_params[[inner_dim]]
          var_ordered <- NULL
          var_unorder_indices <- NULL
          with_transform <- FALSE
          # If the selectors come with an associated variable
          if (!is.null(var_with_selectors_name)) {
            if ((var_with_selectors_name %in% transform_vars) && (!is.null(transform))) {
              with_transform <- TRUE
              if (!is.null(file_dim)) {
                stop("Requested a transformation over the dimension '", 
                     inner_dim, "', wich goes across files. This feature ", 
                     "is not supported. Either do the request without the ",
                     "transformation or request it over dimensions that do ",
                     "not go across files.")
              }
            }
if (debug) {
if (inner_dim %in% dims_to_check) {
print("-> NAME OF THE VARIABLE WITH THE SELECTOR VALUES FOR THE CURRENT INNER DIMENSION:")
print(var_with_selectors_name)
print("-> NAMES OF THE VARIABLES TO BE TRANSFORMED:")
print(transform_vars)
print("-> STRUCTURE OF THE TRANSFORMATION FUNCTION:")
print(str(transform))
}
}
            if (var_with_selectors_name %in% names(picked_vars[[i]])) {
              var_with_selectors <- picked_vars[[i]][[var_with_selectors_name]]
              var_ordered <- picked_vars_ordered[[i]][[var_with_selectors_name]]
              var_unorder_indices <- picked_vars_unorder_indices[[i]][[var_with_selectors_name]]
            } else if (var_with_selectors_name %in% names(picked_common_vars)) {
              var_with_selectors <- picked_common_vars[[var_with_selectors_name]]
              var_ordered <- picked_common_vars_ordered[[var_with_selectors_name]]
              var_unorder_indices <- picked_common_vars_unorder_indices[[var_with_selectors_name]]
            }
            n <- prod(dim(var_with_selectors))
            if (is.null(var_unorder_indices)) {
              var_unorder_indices <- 1:n
            }
            if (with_transform) {
              if (var_with_selectors_name %in% names(transformed_vars[[i]])) {
                m <- prod(dim(transformed_vars[[i]][[var_with_selectors_name]]))
                if (aiat) {
                  var_with_selectors <- transformed_vars[[i]][[var_with_selectors_name]]
                  var_ordered <- transformed_vars_ordered[[i]][[var_with_selectors_name]]
                  var_unorder_indices <- transformed_vars_unorder_indices[[i]][[var_with_selectors_name]]
                }
              } else if (var_with_selectors_name %in% names(transformed_common_vars)) {
                m <- prod(dim(transformed_common_vars[[var_with_selectors_name]]))
                if (aiat) {
                  var_with_selectors <- transformed_common_vars[[var_with_selectors_name]]
                  var_ordered <- transformed_common_vars_ordered[[var_with_selectors_name]]
                  var_unorder_indices <- transformed_common_vars_unorder_indices[[var_with_selectors_name]]
                }
              }
              if (is.null(var_unorder_indices)) {
                var_unorder_indices <- 1:m
              }
            }
if (debug) {
if (inner_dim %in% dims_to_check) {
print("-> SIZE OF ORIGINAL VARIABLE:")
print(n)
print("-> SIZE OF TRANSFORMED VARIABLE:")
if (with_transform) print(m)
print("-> STRUCTURE OF ORDERED VAR:")
print(str(var_ordered))
print("-> UNORDER INDICES:")
print(var_unorder_indices)
}
}
            var_dims <- dim(var_with_selectors)
            var_file_dims <- 1
            if (any(names(var_dims) %in% found_file_dims[[i]])) {
              if (with_transform) {
                stop("Requested transformation for inner dimension '", 
                     inner_dim, "' but provided selectors for such dimension ",
                     "over one or more file dimensions. This is not ",
                     "supported. Either request no transformation for the ",
                     "dimension '", inner_dim, "' or specify the ",
                     "selectors for this dimension without the file dimensions.")
              }
              var_file_dims <- var_dims[which(names(var_dims) %in% found_file_dims[[i]])]
              var_dims <- var_dims[-which(names(var_dims) %in% found_file_dims[[i]])]
            }
##            # Keep the selectors if they correspond to a variable that will be transformed.
##            if (with_transform) {
##              if (var_with_selectors_name %in% names(picked_vars[[i]])) {
##                transformed_var_with_selectors <- transformed_vars[[i]][[var_with_selectors_name]]
##              } else if (var_with_selectors_name %in% names(picked_common_vars)) {
##                transformed_var_with_selectors <- transformed_common_vars[[var_with_selectors_name]]
##              }
##              transformed_var_dims <- dim(transformed_var_with_selectors)
##              transformed_var_file_dims <- 1
##              if (any(names(transformed_var_dims) %in% found_file_dims[[i]])) {
##                transformed_var_file_dims <- transformed_var_dims[which(names(transformed_var_dims) %in% found_file_dims[[i]])]
##                transformed_var_dims <- tranasformed_var_dims[-which(names(transformed_var_dims) %in% found_file_dims[[i]])]
##              }
##if (inner_dim %in% dims_to_check) {
##print("111m")
##print(str(transformed_var_dims))
##}
##
##              m <- prod(transformed_var_dims)
##            }
            # Work out var file dims and inner dims.
            if (inner_dim %in% unlist(inner_dims_across_files)) {
              #TODO: if (chunk_amount != number of chunks in selector_file_dims), crash
              if (length(var_dims) > 1) {
                stop("Specified a '", inner_dim, "_var' for the dimension '", 
                     inner_dim, "', which goes across files (across '", file_dim, 
                     "'). The specified variable, '", var_with_selectors_name, "', has more ",
                     "than one dimension and can not be used as selector variable. ",
                     "Select another variable or fix it in the files.")
              }
            }
            ## TODO HERE::
            #- indices_of_first_files_with_data may change, because array is now extended
            var_full_dims <- dim(var_with_selectors)
            if (!(inner_dim %in% names(var_full_dims))) {
              stop("Could not find the dimension '", inner_dim, "' in ",
                   "the file. Either change the dimension name in ",
                   "your request, adjust the parameter ",
                   "'dim_names_in_files' or fix the dimension name in ",
                   "the file.\n", file_path)
            }
          } else if ((is.numeric(selector_array) && selectors_are_indices) ||
                     (is.character(selector_array) && (length(selector_array) == 1) &&
                      (selector_array %in% c('all', 'first', 'last')) &&
                       !is.null(file_dim_reader))) {
            #### TODO HERE::
            ###- indices_of_first_files_with_data may change, because array is now extended
            # Lines moved above for better performance.
            ##data_dims <- file_dim_reader(file_path, NULL, selectors_of_first_files_with_data[[i]],
            ##                             lapply(dat[[i]][['selectors']][expected_inner_dims[[i]]], '[[', 1))
            if (!(inner_dim %in% names(data_dims))) {
              stop("Could not find the dimension '", inner_dim, "' in ",
                   "the file. Either change the dimension name in ",
                   "your request, adjust the parameter ",
                   "'dim_names_in_files' or fix the dimension name in ",
                   "the file.\n", file_path)
            }
          } else {
            stop(paste0("Can not translate the provided selectors for '", inner_dim, 
                        "' to numeric indices. Provide numeric indices and a ",
                        "'file_dim_reader' function, or a '", inner_dim, 
                        "_var' in order to calculate the indices."))
          }
          # At this point, if no selector variable was provided, the variable 
          # data_dims has been populated. If a selector variable was provided,
          # the variables var_dims, var_file_dims and var_full_dims have been 
          # populated instead.
          fri <- first_round_indices <- NULL
          sri <- second_round_indices <- NULL
          # This variable will keep the indices needed to crop the transformed 
          # variable (the one that has been transformed without being subset 
          # with the first round indices).
          tvi <- tranaformed_variable_indices <- NULL
          ordered_fri <- NULL
          ordered_sri <- NULL
          if ((length(selector_array) == 1) && is.character(selector_array) &&
              (selector_array %in% c('all', 'first', 'last'))) {
            if (is.null(var_with_selectors_name)) {
              fri <- vector('list', length = chunk_amount)
              dim(fri) <- c(chunk_amount)
              sri <- vector('list', length = chunk_amount)
              dim(sri) <- c(chunk_amount)
              if (selector_array == 'all') {
                fri[] <- replicate(chunk_amount, list(1:(data_dims[inner_dim])))
                taken_chunks <- rep(TRUE, chunk_amount)
                #sri <- NULL
              } else if (selector_array == 'first') {
                fri[[1]] <- 1
                taken_chunks[1] <- TRUE
                #sri <- NULL
              } else if (selector_array == 'last') {
                fri[[chunk_amount]] <- data_dims[inner_dim]
                taken_chunks[length(taken_chunks)] <- TRUE
                #sri <- NULL
              }
            } else {
              if ((!is.null(file_dim)) && !(file_dim %in% names(var_file_dims))) {
                stop("The variable '", var_with_selectors_name, "' must also be ",
                     "requested for the file dimension '", file_dim, "' in ",
                     "this configuration.")
              }
              fri <- vector('list', length = prod(var_file_dims))
              dim(fri) <- var_file_dims
              ordered_fri <- fri
              sri <- vector('list', length = prod(var_file_dims))
              dim(sri) <- var_file_dims
              ordered_sri <- sri
              if (selector_array == 'all') {
# TODO: Populate ordered_fri
                ordered_fri[] <- replicate(prod(var_file_dims), list(1:n))
                fri[] <- replicate(prod(var_file_dims), list(var_unorder_indices[1:n]))
                taken_chunks <- rep(TRUE, chunk_amount)
                if (!with_transform) {
                  #fri[] <- replicate(prod(var_file_dims), list(1:n))
                  #taken_chunks <- rep(TRUE, chunk_amount)
                  #sri <- NULL
                } else {
                  ordered_sri[] <- replicate(prod(transformed_var_file_dims), list(1:m))
                  sri[] <- replicate(prod(transformed_var_file_dims), list(1:m))
                  ## var_file_dims instead??
                  #if (!aiat) {
                    #fri[] <- replicate(prod(var_file_dims), list(1:n))
                    #taken_chunks <- rep(TRUE, chunk_amount)
                    #sri[] <- replicate(prod(transformed_var_file_dims), list(1:m))
                  #} else {
                    #fri[] <- replicate(prod(var_file_dims), list(1:n))
                    #taken_chunks <- rep(TRUE, chunk_amount)
                    #sri[] <- replicate(prod(transformed_var_file_dims), list(1:m))
                  #}
                  tvi <- 1:m
                }
              } else if (selector_array == 'first') {
                taken_chunks[1] <- TRUE
                if (!with_transform) {
                  ordered_fri[[1]] <- 1
                  fri[[1]] <- var_unorder_indices[1]
                  #taken_chunks[1] <- TRUE
                  #sri <- NULL
                } else {
                  if (!aiat) {
                    ordered_fri[[1]] <- 1
                    fri[[1]] <- var_unorder_indices[1]
# TODO: TO BE IMPROVED
                    #taken_chunks[1] <- TRUE
                    ordered_sri[[1]] <- 1:ceiling(m / n)
                    sri[[1]] <- 1:ceiling(m / n)
                    tvi <- 1:ceiling(m / n)
                  } else {
                    ordered_fri[[1]] <- 1:ceiling(m / n)
                    fri[[1]] <- var_unorder_indices[1:ceiling(m / n)]
                    #taken_chunks[1] <- TRUE
                    ordered_sri[[1]] <- 1
                    sri[[1]] <- 1
                    tvi <- 1
                  }
                }
              } else if (selector_array == 'last') {
                taken_chunks[length(taken_chunks)] <- TRUE
                if (!with_transform) {
                  ordered_fri[[prod(var_file_dims)]] <- n
                  fri[[prod(var_file_dims)]] <- var_unorder_indices[n]
                  #taken_chunks[length(taken_chunks)] <- TRUE
                  #sri <- NULL
                } else {
                  if (!aiat) {
                    ordered_fri[[prod(var_file_dims)]] <- prod(var_dims)
                    fri[[prod(var_file_dims)]] <- var_unorder_indices[prod(var_dims)]
                    #taken_chunks[length(taken_chunks)] <- TRUE
                    ordered_sri[[prod(var_file_dims)]] <- 1:ceiling(m / n)
                    sri[[prod(var_file_dims)]] <- 1:ceiling(m / n)
# TODO: TO BE IMPROVED. THE TVI MAY BE WRONG IF THERE'S BEEN A REORDERING.
                    tvi <- 1:ceiling(m / n)
                  } else {
                    ordered_fri[[prod(var_file_dims)]] <- (n - ceiling(m / n) + 1):n
                    fri[[prod(var_file_dims)]] <- var_unorder_indices[(n - ceiling(m / n) + 1):n]
                    #taken_chunks[length(taken_chunks)] <- TRUE
                    ordered_sri[[prod(var_file_dims)]] <- 1
                    sri[[prod(var_file_dims)]] <- 1
                    tvi <- 1
                  }
                }
              }
            }
          # If the selectors are not 'all', 'first', 'last', ...
          } else {
            if (!is.null(var_with_selectors_name)) {
              unmatching_file_dims <- which(!(names(var_file_dims) %in% names(selector_file_dims)))
              if ((length(unmatching_file_dims) > 0)) {
                raise_error <- FALSE
                if (is.null(file_dim)) {
                  raise_error <- TRUE
                } else {
                  if (!((length(unmatching_file_dims) == 1) && 
                        (names(var_file_dims)[unmatching_file_dims] == file_dim) &&
                        (inner_dim %in% names(selector_inner_dims)))) {
                    raise_error <- TRUE
                  }
                }
                if (raise_error) {
                  stop("Provided selectors for the dimension '", inner_dim, "' must have as many ",
                       "file dimensions as the variable the dimension is defined along, '", 
                       var_with_selectors_name, "', with the exceptions of the file pattern dimension ('",
                       found_pattern_dim, "') and any depended file dimension (if specified as ",
                       "depended dimension in parameter 'inner_dims_across_files' and the ",
                       "depending file dimension is present in the provided selector array).")
                }
              }
              if (any(dim(var_with_selectors)[names(selector_file_dims)] != selector_file_dims)) {
                stop("Size of selector file dimensions must mach size of requested ",
                     "variable dimensions.")
              }
            }
            ## TODO: If var dimensions are not in the same order as selector dimensions, reorder
            if (is.null(names(selector_file_dims))) {
              if (is.null(file_dim)) {
                fri_dims <- 1
              } else {
                fri_dims <- chunk_amount
                names(fri_dims) <- file_dim
              }
            } else {
              fri_dim_names <- names(selector_file_dims)
              if (!is.null(file_dim)) {
                fri_dim_names <- c(fri_dim_names, file_dim)
              }
              fri_dim_names <- found_file_dims[[i]][which(found_file_dims[[i]] %in% fri_dim_names)]
              fri_dims <- rep(NA, length(fri_dim_names))
              names(fri_dims) <- fri_dim_names
              fri_dims[names(selector_file_dims)] <- selector_file_dims
              if (!is.null(file_dim)) {
                fri_dims[file_dim] <- chunk_amount
              }
            }
            fri <- vector('list', length = prod(fri_dims))
            dim(fri) <- fri_dims
            sri <- vector('list', length = prod(fri_dims))
            dim(sri) <- fri_dims
            selector_file_dim_array <- array(1:prod(selector_file_dims), dim = selector_file_dims)
            selector_store_position <- fri_dims
            for (j in 1:prod(dim(selector_file_dim_array))) {
              selector_indices_to_take <- which(selector_file_dim_array == j, arr.ind = TRUE)[1, ]
              names(selector_indices_to_take) <- names(selector_file_dims)
              selector_store_position[names(selector_indices_to_take)] <- selector_indices_to_take
              sub_array_of_selectors <- Subset(selector_array, names(selector_indices_to_take),
                                               as.list(selector_indices_to_take), drop = 'selected')
if (debug) {
if (inner_dim %in% dims_to_check) {
print("-> ITERATING OVER FILE DIMENSIONS OF THE SELECTORS.")
print("-> STRUCTURE OF A SUB ARRAY:")
print(str(sub_array_of_selectors))
print("-> STRUCTURE OF THE VARIABLE WITH SELECTORS:")
print(str(var_with_selectors))
print(dim(var_with_selectors))
}
}
              if (selectors_are_indices) {
                sub_array_of_values <- NULL
              #} else if (!is.null(var_ordered)) {
              #  sub_array_of_values <- var_ordered
              } else {
                if (length(var_file_dims) > 0) {
                  var_indices_to_take <- selector_indices_to_take[which(names(selector_indices_to_take) %in% names(var_file_dims))]
                  sub_array_of_values <- Subset(var_with_selectors, names(var_indices_to_take),
                                                as.list(var_indices_to_take), drop = 'selected')
                } else {
                  sub_array_of_values <- var_with_selectors
                }
              }
if (debug) {
if (inner_dim %in% dims_to_check) {
print("-> STRUCTURE OF THE SUB ARRAY FROM THE VARIABLE CORRESPONDING TO THE SUB ARRAY OF SELECTORS")
print(str(sub_array_of_values))
print(dim(sub_array_of_values))
print("-> NAME OF THE FILE DIMENSION THE CURRENT INNER DIMENSION EXTENDS ALONG:")
print(file_dim)
}
}
              if ((!is.null(file_dim) && (file_dim %in% names(selector_file_dims))) || is.null(file_dim)) {
                if (length(sub_array_of_selectors) > 0) {
if (debug) {
if (inner_dim %in% dims_to_check) {
print("-> THE INNER DIMENSION DOES NOT GO ACROSS ANY FILE DIMENSION OR IT DOES BUT IS IN THE PROVIDED SELECTOR ARRAY.")
}
}
                  if (selectors_are_indices) {
                    if (!is.null(var_with_selectors_name)) {
                      max_allowed <- ifelse(aiat, m, n)
                    } else {
                      max_allowed <- data_dims[inner_dim]
                    }
                    if (any(na.omit(unlist(sub_array_of_selectors)) > max_allowed) ||
                        any(na.omit(unlist(sub_array_of_selectors)) < 1)) {
                      stop("Provided indices out of range for dimension '", inner_dim, "' ", 
                           "for dataset '", dat[[i]][['name']], "' (accepted range: 1 to ", 
                           max_allowed, ").")
                    }
                  }
                  
                  # The selector_checker will return either a vector of indices or a list
                  # with the first and last desired indices.
                  goes_across_prime_meridian <- FALSE
                  if (!is.null(var_ordered) && !selectors_are_indices) {
                    if (!is.null(dim_reorder_params[[inner_dim]])) {
                      if (is.list(sub_array_of_selectors)) {
                        sub_array_reordered <- dim_reorder_params[[inner_dim]](unlist(sub_array_of_selectors))
                        sub_array_unorder <- sort(sub_array_reordered$ix, index.return = TRUE)$ix
                        sub_array_of_selectors <- as.list(sub_array_reordered$x[sub_array_unorder])
                        is_circular_dim <- attr(dim_reorder_params[[inner_dim]], 'circular')
                        if (!is.null(is_circular_dim)) {
                          if (is_circular_dim) {
                            goes_across_prime_meridian <- abs(sub_array_of_selectors[[1]]) > abs(sub_array_of_selectors[[2]])
                            ## TODO: if (bounds[1] > bounds[2]) goes_across_prime_meridian <- !goes_across_prime_meridian
                          }
                        }
                      } else {
                        sub_array_of_selectors <- dim_reorder_params[[inner_dim]](sub_array_of_selectors)$x
                      }
                    }
                    sub_array_of_indices <- selector_checker(sub_array_of_selectors, var_ordered,
                                                             tolerance = if (aiat) {
                                                                           NULL
                                                                         } else {
                                                                           tolerance_params[[inner_dim]]
                                                                         })
                  } else {
                    sub_array_of_indices <- selector_checker(sub_array_of_selectors, sub_array_of_values,
                                                             tolerance = if (aiat) {
                                                                           NULL
                                                                         } else {
                                                                           tolerance_params[[inner_dim]]
                                                                         })
                  }
                  # The sub_array_of_indices now contains numeric indices of the values to be taken.
if (debug) {
if (inner_dim %in% dims_to_check) {
print("-> TRANSFORMATION REQUESTED?")
print(with_transform)
print("-> BETA:")
print(beta)
}
}
                  if (with_transform) {
                    # If there is a transformation and selector values are provided, these
                    # selectors will be processed in the same way either if aiat = TRUE or
                    # aiat = FALSE.
## TODO: If sub_array_of_selectors was integer and aiat then... do what's commented 50 lines below.
##       otherwise, do what's coded.
if (debug) {
if (inner_dim %in% dims_to_check) {
print("-> SELECTORS REQUESTED BEFORE TRANSFORM.")
}
}
                    if (goes_across_prime_meridian) {
                      sub_array_of_fri <- 1:n
                      #gap_width <- sub_array_of_indices[[1]] - sub_array_of_indices[[2]] - 1
                      #sub_array_of_fri <- c((1:(sub_array_of_indices[[2]] + min(gap_width, beta))),
                      #                      (sub_array_of_indices[[1]] - min(gap_width, beta)):n)
                    } else {
                      if (is.list(sub_array_of_indices)) {
                        sub_array_of_indices <- sub_array_of_indices[[1]]:sub_array_of_indices[[2]]
                      }
                      first_index <- min(unlist(sub_array_of_indices))
                      last_index <- max(unlist(sub_array_of_indices))
                      start_padding <- min(beta, first_index - 1)
                      end_padding <- min(beta, n - last_index)
                      sub_array_of_fri <- (first_index - start_padding):(last_index + end_padding)
                    }
                    subset_vars_to_transform <- vars_to_transform
                    if (!is.null(var_ordered)) {
                      subset_vars_to_transform[[var_with_selectors_name]] <- Subset(var_ordered, inner_dim, sub_array_of_fri)
                    } else {
                      subset_vars_to_transform[[var_with_selectors_name]] <- Subset(sub_array_of_values, inner_dim, sub_array_of_fri)
                    }
                    transformed_subset_var <- do.call(transform, c(list(data_array = NULL,
                                                                        variables = subset_vars_to_transform,
                                                                        file_dims = found_file_dims[[i]]),
                                                                        transform_params))$variables[[var_with_selectors_name]]
                    # Sorting the transformed variable and working out the indices again after transform.
                    if (!is.null(dim_reorder_params[[inner_dim]])) {
                      transformed_subset_var_reorder <- dim_reorder_params[[inner_dim]](transformed_subset_var)
                      transformed_subset_var <- transformed_subset_var_reorder$x
                      transformed_subset_var_unorder <- sort(transformed_subset_var_reorder$ix, index.return = TRUE)$ix
                    } else {
                      transformed_subset_var_unorder <- 1:length(transformed_subset_var)
                    }
                    sub_array_of_sri <- selector_checker(sub_array_of_selectors, transformed_subset_var,
                                                         tolerance = if (aiat) {
                                                                       tolerance_params[[inner_dim]]
                                                                     } else {
                                                                       NULL
                                                                     })
                    if (goes_across_prime_meridian) {
                      sub_array_of_sri <- c(1:sub_array_of_sri[[2]], sub_array_of_sri[[1]]:length(transformed_subset_var))
                      #sub_array_of_sri <- c(sub_array_of_sri[[1]]:length(transformed_subset_var), 1:sub_array_of_sri[[2]])
                    } else if (is.list(sub_array_of_sri)) {
                      sub_array_of_sri <- sub_array_of_sri[[1]]:sub_array_of_sri[[2]]
                    }
                    ordered_sri <- sub_array_of_sri
                    sub_array_of_sri <- transformed_subset_var_unorder[sub_array_of_sri]
                    # In this case, the tvi are not defined and the 'transformed_subset_var'
                    # will be taken instead of the var transformed before in the code.
if (debug) {
if (inner_dim %in% dims_to_check) {
print("-> FIRST INDEX:")
print(first_index)
print("-> LAST INDEX:")
print(last_index)
print("-> STRUCTURE OF FIRST ROUND INDICES:")
print(str(sub_array_of_fri))
print("-> STRUCTURE OF SECOND ROUND INDICES:")
print(str(sub_array_of_sri))
print("-> STRUCTURE OF TRANSFORMED VARIABLE INDICES:")
print(str(tvi))
}
}
###                    # If the selectors are expressed after transformation
###                    } else {
###if (debug) {
###if (inner_dim %in% dims_to_check) {
###print("-> SELECTORS REQUESTED AFTER TRANSFORM.")
###}
###}
###                      if (goes_across_prime_meridian) {
###                        sub_array_of_indices <- c(sub_array_of_indices[[1]]:m,
###                                                    1:sub_array_of_indices[[2]])
###                      }
###                      first_index <- min(unlist(sub_array_of_indices))
###                      last_index <- max(unlist(sub_array_of_indices))
###                      first_index_before_transform <- max(transform_indices(first_index, m, n) - beta, 1)
###                      last_index_before_transform <- min(transform_indices(last_index, m, n) + beta, n)
###                      sub_array_of_fri <- first_index_before_transform:last_index_before_transform
###                      n_of_extra_cells <- round(beta / n * m)
###                      if (is.list(sub_array_of_indices) && (length(sub_array_of_indices) > 1)) {
###                        sub_array_of_sri <- 1:(last_index - first_index + 1) 
###                        if (is.null(tvi)) {
###                          tvi <- sub_array_of_sri + first_index - 1
###                        }
###                      } else {
###                        sub_array_of_sri <- sub_array_of_indices - first_index + 1
###                        if (is.null(tvi)) {
###                          tvi <- sub_array_of_indices
###                        }
###                      }
###                      sub_array_of_sri <- sub_array_of_sri + n_of_extra_cells
                    sri <- do.call('[[<-', c(list(x = sri), as.list(selector_store_position),
                                             list(value = sub_array_of_sri)))
                  } else {
                    if (goes_across_prime_meridian) {
                      #sub_array_of_fri <- 1:n
                      sub_array_of_fri <- c(1:sub_array_of_indices[[2]], sub_array_of_indices[[1]]:n)
                    } else if (is.list(sub_array_of_indices)) {
                      sub_array_of_fri <- sub_array_of_indices[[1]]:sub_array_of_indices[[2]]
                    } else {
                      sub_array_of_fri <- sub_array_of_indices
                    }
                  }
                  if (!is.null(var_unorder_indices)) {
                    if (is.null(ordered_fri)) {
                      ordered_fri <- sub_array_of_fri
                    }
                    sub_array_of_fri <- var_unorder_indices[sub_array_of_fri]
                  }
                  fri <- do.call('[[<-', c(list(x = fri), as.list(selector_store_position),
                                           list(value = sub_array_of_fri)))
                  if (!is.null(file_dim)) {
                    taken_chunks[selector_store_position[[file_dim]]] <- TRUE
                  } else {
                    taken_chunks <- TRUE
                  }
                }
              } else {
if (debug) {
if (inner_dim %in% dims_to_check) {
print("-> THE INNER DIMENSION GOES ACROSS A FILE DIMENSION.")
}
}
                if (inner_dim %in% names(dim(sub_array_of_selectors))) {
                  if (is.null(var_with_selectors_name)) {
                    if (any(na.omit(unlist(sub_array_of_selectors)) < 1) ||
                        any(na.omit(unlist(sub_array_of_selectors)) > data_dims[inner_dim] * chunk_amount)) {
                      stop("Provided indices out of range for dimension '", inner_dim, "' ", 
                           "for dataset '", dat[[i]][['name']], "' (accepted range: 1 to ", 
                           data_dims[inner_dim] * chunk_amount, ").")
                    }
                  } else {
                    if (inner_dim %in% names(dim(sub_array_of_values))) {
                      inner_dim_pos_in_sub_array <- which(names(dim(sub_array_of_values)) == inner_dim)
                      if (inner_dim_pos_in_sub_array != 1) {
                        new_sub_array_order <- (1:length(dim(sub_array_of_values)))[-inner_dim_pos_in_sub_array]
                        new_sub_array_order <- c(inner_dim_pos_in_sub_array, new_sub_array_order)
                        sub_array_of_values <- .aperm2(sub_array_of_values, new_sub_array_order)
                      }
                    }
                  }
                  inner_dim_pos_in_sub_array <- which(names(dim(sub_array_of_selectors)) == inner_dim)
                  if (inner_dim_pos_in_sub_array != 1) {
                    new_sub_array_order <- (1:length(dim(sub_array_of_selectors)))[-inner_dim_pos_in_sub_array]
                    new_sub_array_order <- c(inner_dim_pos_in_sub_array, new_sub_array_order)
                    sub_array_of_selectors <- .aperm2(sub_array_of_selectors, new_sub_array_order)
                  }
                  sub_array_of_indices <- selector_checker(sub_array_of_selectors, sub_array_of_values,
                                                           tolerance = tolerance_params[[inner_dim]])
                  sub_array_is_list <- FALSE
                  if (is.list(sub_array_of_indices)) {
                    sub_array_is_list <- TRUE
                    sub_array_of_indices <- unlist(sub_array_of_indices)
                  }
                  if (is.null(var_with_selectors_name)) {
                    indices_chunk <- floor((sub_array_of_indices - 1) / data_dims[inner_dim]) + 1
                    transformed_indices <- ((sub_array_of_indices - 1) %% data_dims[inner_dim]) + 1
                  } else {
                    indices_chunk <- floor((sub_array_of_indices - 1) / var_full_dims[inner_dim]) + 1
                    transformed_indices <- ((sub_array_of_indices - 1) %% var_full_dims[inner_dim]) + 1
                  }
                  if (sub_array_is_list) {
                    sub_array_of_indices <- as.list(sub_array_of_indices)
                  }
if (debug) {
if (inner_dim %in% dims_to_check) {
print("-> GOING TO ITERATE ALONG CHUNKS.")
}
}
                  for (chunk in 1:chunk_amount) {
                    if (!is.null(names(selector_store_position))) {
                      selector_store_position[file_dim] <- chunk
                    } else {
                      selector_store_position <- chunk
                    }
                    chunk_selectors <- transformed_indices[which(indices_chunk == chunk)]
                    sub_array_of_indices <- chunk_selectors
                    if (with_transform) {
                      # If the provided selectors are expressed in the world
                      # before transformation
                      if (!aiat) {
                        first_index <- min(unlist(sub_array_of_indices))
                        last_index <- max(unlist(sub_array_of_indices))
                        sub_array_of_fri <- max(c(first_index - beta, 1)):min(c(last_index + beta, n))
                        sub_array_of_sri <- transform_indices(unlist(sub_array_of_indices) - first_index + 1, n, m)
                        if (is.list(sub_array_of_indices)) {
                          if (length(sub_array_of_sri) > 1) {
                            sub_array_of_sri <- sub_array_of_sri[[1]]:sub_array_of_sri[[2]]
                          }
                        }
##TODO: TRANSFORM SUBSET VARIABLE AS ABOVE, TO COMPUTE SRI
                      # If the selectors are expressed after transformation
                      } else {
                        first_index <- min(unlist(sub_array_of_indices))
                        last_index <- max(unlist(sub_array_of_indices))
                        first_index_before_transform <- max(transform_indices(first_index, m, n) - beta, 1)
                        last_index_before_transform <- min(transform_indices(last_index, m, n) + beta, n)
                        sub_array_of_fri <- first_index_before_transform:last_index_before_transform
                        if (is.list(sub_array_of_indices) && (length(sub_array_of_indices) > 1)) {
                          sub_array_of_sri <- 1:(last_index - first_index + 1) + 
                                              round(beta / n * m) 
                        } else {
                          sub_array_of_sri <- sub_array_of_indices - first_index + 1 +
                                              round(beta / n * m)
                        }
##TODO: FILL IN TVI
                      }
                      sri <- do.call('[[<-', c(list(x = sri), as.list(selector_store_position),
                                               list(value = sub_array_of_sri)))
                      if (length(sub_array_of_sri) > 0) {
                        taken_chunks[chunk] <- TRUE
                      }
                    } else {
                      sub_array_of_fri <- sub_array_of_indices
                      if (length(sub_array_of_fri) > 0) {
                        taken_chunks[chunk] <- TRUE
                      }
                    }
                    if (!is.null(var_unorder_indices)) {
                      ordered_fri <- sub_array_of_fri
                      sub_array_of_fri <- var_unorder_indices[sub_array_of_fri]
                    }
                    fri <- do.call('[[<-', c(list(x = fri), as.list(selector_store_position),
                                             list(value = sub_array_of_fri)))
                  }
if (debug) {
if (inner_dim %in% dims_to_check) {
print("-> FINISHED ITERATING ALONG CHUNKS")
}
}
                } else {
                  stop("Provided array of indices for dimension '", inner_dim, "', ",
                       "which goes across the file dimension '", file_dim, "', but ",
                       "the provided array does not have the dimension '", inner_dim, 
                       "', which is mandatory.")
                }
              }
            }
          }
if (debug) {
if (inner_dim %in% dims_to_check) {
print("-> PROCEEDING TO CROP VARIABLES")
}
}
          #if ((length(selector_array) == 1) && (selector_array %in% c('all', 'first', 'last'))) {
            #if (!is.null(var_with_selectors_name) || (is.null(var_with_selectors_name) && is.character(selector_array) &&
            #    (length(selector_array) == 1) && (selector_array %in% c('all', 'first', 'last')))) {
              empty_chunks <- which(!taken_chunks)
              if (length(empty_chunks) >= length(taken_chunks)) {
                stop("Selectors do not match any of the possible values for the dimension '", inner_dim, "'.")
              }
              if (length(empty_chunks) > 0) {
#                # Get the first group of chunks to remove, and remove them. 
#                # E.g., from c(1, 2, 4, 5, 6, 8, 9) remove only 1 and 2
#                dist <- abs(rev(empty_chunks) - c(rev(empty_chunks)[1] - 1, head(rev(empty_chunks), length(rev(empty_chunks)) - 1)))
#                if (all(dist == 1)) {
#                  start_chunks_to_remove <- NULL
#                } else {
#                  first_chunk_to_remove <- tail(which(dist > 1), 1)
#                  start_chunks_to_remove <- rev(rev(empty_chunks)[first_chunk_to_remove:length(empty_chunks)])
#                }
#                # Get the last group of chunks to remove, and remove them. 
#                # E.g., from c(1, 2, 4, 5, 6, 8, 9) remove only 8 and 9
#                dist <- abs(empty_chunks - c(empty_chunks[1] - 1, head(empty_chunks, length(empty_chunks) - 1)))
#                if (all(dist == 1)) {
#                  first_chunk_to_remove <- 1
#                } else {
#                  first_chunk_to_remove <- tail(which(dist > 1), 1)
#                }
#                end_chunks_to_remove <- empty_chunks[first_chunk_to_remove:length(empty_chunks)]
#                chunks_to_keep <- which(!((1:length(taken_chunks)) %in% c(start_chunks_to_remove, end_chunks_to_remove)))
                chunks_to_keep <- which(taken_chunks)
                dims_to_crop[[file_dim]] <- c(dims_to_crop[[file_dim]], list(chunks_to_keep))
#                found_indices <- Subset(found_indices, file_dim, chunks_to_keep)
#                # Crop dataset variables file dims.
#                for (picked_var in names(picked_vars[[i]])) {
#                  if (file_dim %in% names(dim(picked_vars[[i]][[picked_var]]))) {
#                    picked_vars[[i]][[picked_var]] <- Subset(picked_vars[[i]][[picked_var]], file_dim, chunks_to_keep)
#                  }
#                }
              }
            #}
            dat[[i]][['selectors']][[inner_dim]] <- list(fri = fri, sri = sri)
            # Crop dataset variables inner dims.
            # Crop common variables inner dims.
            types_of_var_to_crop <- 'picked'
            if (with_transform) {
              types_of_var_to_crop <- c(types_of_var_to_crop, 'transformed')
            }
            if (!is.null(dim_reorder_params[[inner_dim]])) {
              types_of_var_to_crop <- c(types_of_var_to_crop, 'reordered')
            }
            for (type_of_var_to_crop in types_of_var_to_crop) {
              if (type_of_var_to_crop == 'transformed') {
                if (is.null(tvi)) {
                  if (!is.null(dim_reorder_params[[inner_dim]])) {
                    crop_indices <- unique(unlist(ordered_sri))
                  } else {
                    crop_indices <- unique(unlist(sri))
                  }
                } else {
                  crop_indices <- unique(unlist(tvi))
                }
                vars_to_crop <- transformed_vars[[i]]
                common_vars_to_crop <- transformed_common_vars
              } else if (type_of_var_to_crop == 'reordered') {
                crop_indices <- unique(unlist(ordered_fri))
                vars_to_crop <- picked_vars_ordered[[i]]
                common_vars_to_crop <- picked_common_vars_ordered
              } else {
                crop_indices <- unique(unlist(fri))
                vars_to_crop <- picked_vars[[i]]
                common_vars_to_crop <- picked_common_vars
              }
              for (var_to_crop in names(vars_to_crop)) {
                if (inner_dim %in% names(dim(vars_to_crop[[var_to_crop]]))) {
                  if (!is.null(crop_indices)) {
                    if (type_of_var_to_crop == 'transformed') {
                      if (!aiat) {
                        vars_to_crop[[var_to_crop]] <- Subset(transformed_subset_var, inner_dim, crop_indices)
                      } else {
                        vars_to_crop[[var_to_crop]] <- Subset(vars_to_crop[[var_to_crop]], inner_dim, crop_indices)
                      }
                    } else {
                      vars_to_crop[[var_to_crop]] <- Subset(vars_to_crop[[var_to_crop]], inner_dim, crop_indices)
                    }
                  }
                }
              }
              if (i == length(dat)) {
                for (common_var_to_crop in names(common_vars_to_crop)) {
                  if (inner_dim %in% names(dim(common_vars_to_crop[[common_var_to_crop]]))) {
                    common_vars_to_crop[[common_var_to_crop]] <- Subset(common_vars_to_crop[[common_var_to_crop]], inner_dim, crop_indices)
                  }
                }
              }
              if (type_of_var_to_crop == 'transformed') {
                if (!is.null(vars_to_crop)) {
                  transformed_vars[[i]] <- vars_to_crop
                }
                if (i == length(dat)) {
                  transformed_common_vars <- common_vars_to_crop
                }
              } else if (type_of_var_to_crop == 'reordered') {
                if (!is.null(vars_to_crop)) {
                  picked_vars_ordered[[i]] <- vars_to_crop
                }
                if (i == length(dat)) {
                  picked_common_vars_ordered <- common_vars_to_crop
                }
              } else {
                if (!is.null(vars_to_crop)) {
                  picked_vars[[i]] <- vars_to_crop
                }
                if (i == length(dat)) {
                  picked_common_vars <- common_vars_to_crop
                }
              }
            }
          #}
        }
        # After the selectors have been picked (using the original variables), 
        # the variables are transformed. At that point, the original selectors
        # for the transformed variables are also kept in the variable original_selectors.
#print("L")
      }
    }
  }
#  if (!is.null(transformed_common_vars)) {
#    picked_common_vars[names(transformed_common_vars)] <- transformed_common_vars
#  }
  # Remove the trailing chunks, if any.
  for (file_dim in names(dims_to_crop)) {
#    indices_to_keep <- min(sapply(dims_to_crop[[file_dim]], min)):max(sapply(dims_to_crop[[file_dim]], max))
    ## TODO: Merge indices in dims_to_crop with some advanced mechanism?
    indices_to_keep <- unique(unlist(dims_to_crop[[file_dim]]))
    array_of_files_to_load <- Subset(array_of_files_to_load, file_dim, indices_to_keep)
    array_of_not_found_files <- Subset(array_of_not_found_files, file_dim, indices_to_keep)
    for (i in 1:length(dat)) {
      # Crop selectors
      for (selector_dim in names(dat[[i]][['selectors']])) {
        if (selector_dim == file_dim) {
          for (j in 1:length(dat[[i]][['selectors']][[selector_dim]][['fri']])) {
            dat[[i]][['selectors']][[selector_dim]][['fri']][[j]] <- dat[[i]][['selectors']][[selector_dim]][['fri']][[j]][indices_to_keep]
          }
          for (j in 1:length(dat[[i]][['selectors']][[selector_dim]][['sri']])) {
            dat[[i]][['selectors']][[selector_dim]][['sri']][[j]] <- dat[[i]][['selectors']][[selector_dim]][['sri']][[j]][indices_to_keep]
          }
        }
        if (file_dim %in% names(dim(dat[[i]][['selectors']][[selector_dim]][['fri']]))) {
          dat[[i]][['selectors']][[selector_dim]][['fri']] <- Subset(dat[[i]][['selectors']][[selector_dim]][['fri']], file_dim, indices_to_keep)
          dat[[i]][['selectors']][[selector_dim]][['sri']] <- Subset(dat[[i]][['selectors']][[selector_dim]][['sri']], file_dim, indices_to_keep)
        }
      }
      # Crop dataset variables file dims.
      for (picked_var in names(picked_vars[[i]])) {
        if (file_dim %in% names(dim(picked_vars[[i]][[picked_var]]))) {
          picked_vars[[i]][[picked_var]] <- Subset(picked_vars[[i]][[picked_var]], file_dim, indices_to_keep)
        }
      }
      for (transformed_var in names(transformed_vars[[i]])) {
        if (file_dim %in% names(dim(transformed_vars[[i]][[transformed_var]]))) {
          transformed_vars[[i]][[transformed_var]] <- Subset(transformed_vars[[i]][[transformed_var]], file_dim, indices_to_keep)
        }
      }
    }
    # Crop common variables file dims.
    for (picked_common_var in names(picked_common_vars)) {
      if (file_dim %in% names(dim(picked_common_vars[[picked_common_var]]))) {
        picked_common_vars[[picked_common_var]] <- Subset(picked_common_vars[[picked_common_var]], file_dim, indices_to_keep)
      }
    }
    for (transformed_common_var in names(transformed_common_vars)) {
      if (file_dim %in% names(dim(transformed_common_vars[[transformed_common_var]]))) {
        transformed_common_vars[[transformed_common_var]] <- Subset(transformed_common_vars[[transformed_common_var]], file_dim, indices_to_keep)
      }
    }
  }
  # Calculate the size of the final array.
  total_inner_dims <- NULL
  for (i in 1:length(dat)) {
    if (dataset_has_files[i]) {
      inner_dims <- expected_inner_dims[[i]]
      inner_dims <- sapply(inner_dims, 
        function(x) {
          if (!all(sapply(dat[[i]][['selectors']][[x]][['sri']], is.null))) {
            max(sapply(dat[[i]][['selectors']][[x]][['sri']], length))
          } else {
            if (length(var_params[[x]]) > 0) {
              if (var_params[[x]] %in% names(transformed_vars[[i]])) {
                length(transformed_vars[[i]][[var_params[[x]]]])
              } else if (var_params[[x]] %in% names(transformed_common_vars)) {
                length(common_transformed_vars[[var_params[[x]]]])
              } else {
                max(sapply(dat[[i]][['selectors']][[x]][['fri']], length))
              }
            } else {
              max(sapply(dat[[i]][['selectors']][[x]][['fri']], length))
            }
          }
        })
      names(inner_dims) <- expected_inner_dims[[i]]
      if (is.null(total_inner_dims)) {
        total_inner_dims <- inner_dims
      } else {
        new_dims <- .MergeArrayDims(total_inner_dims, inner_dims)
        total_inner_dims <- pmax(new_dims[[1]], new_dims[[2]])
      }
    }
  }
  new_dims <- .MergeArrayDims(dim(array_of_files_to_load), total_inner_dims)
  final_dims <- pmax(new_dims[[1]], new_dims[[2]])[dim_names]

  ########## CREATING THE SHARED MATRIX AND DISPATCHING WORK PIECES ###########
  # TODO: try performance of storing all in cols instead of rows
  # Create the shared memory array, and a pointer to it, to be sent
  # to the work pieces.
  data_array <- big.matrix(nrow = prod(final_dims), ncol = 1)
  shared_matrix_pointer <- describe(data_array)
  if (is.null(num_procs)) {
    num_procs <- ceiling(availableCores() / 2)
  }
  # Creating a shared tmp folder to store metadata from each chunk
  array_of_metadata_flags <- array(FALSE, dim = dim(array_of_files_to_load))
  metadata_indices_to_load <- as.list(rep(1, length(dim(array_of_files_to_load))))
  names(metadata_indices_to_load) <- names(dim(array_of_files_to_load))
  metadata_indices_to_load[metadata_dims] <- as.list(rep(TRUE, length(metadata_dims)))
  array_of_metadata_flags <- do.call('[<-', c(list(array_of_metadata_flags),  metadata_indices_to_load,
                                              list(value = rep(TRUE, prod(dim(array_of_files_to_load)[metadata_dims])))))
  metadata_file_counter <- 0
  metadata_folder <- tempfile('metadata')
  dir.create(metadata_folder)
  # Build the work pieces, each with:
  # - file path
  # - total size (dims) of store array
  # - start position in store array
  # - file selectors (to provide extra info. useful e.g. to select variable)
  # - indices to take from file
  work_pieces <- list()
  for (i in 1:length(dat)) {
    if (dataset_has_files[i]) {
      selectors <- dat[[i]][['selectors']]
      file_dims <- found_file_dims[[i]]
      inner_dims <- expected_inner_dims[[i]]
      sub_array_dims <- final_dims[file_dims]
      sub_array_dims[found_pattern_dim] <- 1
      sub_array_of_files_to_load <- array(1:prod(sub_array_dims), 
                                          dim = sub_array_dims)
      names(dim(sub_array_of_files_to_load)) <- names(sub_array_dims)
      # Detect which of the dimensions of the dataset go across files.
      file_dim_across_files <- lapply(inner_dims, 
        function(x) {
          dim_across <- sapply(inner_dims_across_files, function(y) x %in% y)
          if (any(dim_across)) {
            names(inner_dims_across_files)[which(dim_across)[1]]
          } else {
            NULL
          }
        })
      names(file_dim_across_files) <- inner_dims
      j <- 1
      while (j <= prod(sub_array_dims)) {
        # Work out file path.
        file_to_load_sub_indices <- which(sub_array_of_files_to_load == j, arr.ind = TRUE)[1, ]
        names(file_to_load_sub_indices) <- names(sub_array_dims)
        file_to_load_sub_indices[found_pattern_dim] <- i
        big_dims <- rep(1, length(dim(array_of_files_to_load)))
        names(big_dims) <- names(dim(array_of_files_to_load))
        file_to_load_indices <- .MergeArrayDims(file_to_load_sub_indices, big_dims)[[1]]
        file_to_load <- do.call('[[', c(list(array_of_files_to_load), 
                                        as.list(file_to_load_indices)))
        not_found_file <- do.call('[[', c(list(array_of_not_found_files),
                                          as.list(file_to_load_indices)))
        load_file_metadata <- do.call('[', c(list(array_of_metadata_flags), 
                                             as.list(file_to_load_indices)))
        if (load_file_metadata) {
          metadata_file_counter <- metadata_file_counter + 1
        }
        if (!is.na(file_to_load) && !not_found_file) {
          # Work out indices to take
          first_round_indices <- lapply(inner_dims, 
            function (x) {
              if (is.null(file_dim_across_files[[x]])) {
                selectors[[x]][['fri']][[1]]
              } else {
                var_file_dims <- dim(selectors[inner_dims][[x]][['fri']])
                which_indices <- file_to_load_sub_indices[which(names(sub_array_dims) %in% names(var_file_dims))] 
                do.call('[[', c(list(selectors[[x]][['fri']]), as.list(which_indices)))
              }
            })
          names(first_round_indices) <- inner_dims
          second_round_indices <- lapply(inner_dims, 
            function (x) {
              if (is.null(file_dim_across_files[[x]])) {
                selectors[[x]][['sri']][[1]]
              } else {
                var_file_dims <- dim(selectors[inner_dims][[x]][['sri']])
                which_indices <- file_to_load_sub_indices[which(names(sub_array_dims) %in% names(var_file_dims))] 
                do.call('[[', c(list(selectors[[x]][['sri']]), as.list(which_indices)))
              }
            })
if (debug) {
print("-> BUILDING A WORK PIECE")
#print(str(selectors))
}
          names(second_round_indices) <- inner_dims
          if (!any(sapply(first_round_indices, length) == 0)) {
            work_piece <- list()
            work_piece[['first_round_indices']] <- first_round_indices
            work_piece[['second_round_indices']] <- second_round_indices
            work_piece[['file_indices_in_array_of_files']] <- file_to_load_indices
            work_piece[['file_path']] <- file_to_load
            work_piece[['store_dims']] <- final_dims
            # Work out store position
            store_position <- final_dims
            store_position[names(file_to_load_indices)] <- file_to_load_indices
            store_position[inner_dims] <- rep(1, length(inner_dims))
            work_piece[['store_position']] <- store_position
            # Work out file selectors
            file_selectors <- sapply(file_dims, 
              function (x) {
                vector_to_pick <- 1
                if (x %in% names(depending_file_dims)) {
                  vector_to_pick <- file_to_load_indices[depending_file_dims[[x]]]
                }
                selectors[file_dims][[x]][[vector_to_pick]][file_to_load_indices[x]]
              })
            names(file_selectors) <- file_dims
            work_piece[['file_selectors']] <- file_selectors
            # Send variables for transformation
            if (!is.null(transform) && (length(transform_vars) > 0)) {
              vars_to_transform <- NULL
              picked_vars_to_transform <- which(names(picked_vars[[i]]) %in% transform_vars)
              if (length(picked_vars_to_transform) > 0) {
                picked_vars_to_transform <- names(picked_vars[[i]])[picked_vars_to_transform]
                vars_to_transform <- c(vars_to_transform, picked_vars[[i]][picked_vars_to_transform])
                if (any(picked_vars_to_transform %in% names(picked_vars_ordered[[i]]))) {
                  picked_vars_ordered_to_transform <- picked_vars_to_transform[which(picked_vars_to_transform %in% names(picked_vars_ordered[[i]]))]
                  vars_to_transform[picked_vars_ordered_to_transform] <- picked_vars_ordered[[i]][picked_vars_ordered_to_transform]
                }
              }
              picked_common_vars_to_transform <- which(names(picked_common_vars) %in% transform_vars)
              if (length(picked_common_vars_to_transform) > 0) {
                picked_common_vars_to_transform <- names(picked_common_vars)[picked_common_vars_to_transform]
                vars_to_transform <- c(vars_to_transform, picked_common_vars[picked_common_vars_to_transform])
                if (any(picked_common_vars_to_transform %in% names(picked_common_vars_ordered))) {
                  picked_common_vars_ordered_to_transform <- picked_common_vars_to_transform[which(picked_common_vars_to_transform %in% names(picked_common_vars_ordered))]
                  vars_to_transform[picked_common_vars_ordered_to_transform] <- picked_common_vars_ordered[picked_common_vars_ordered_to_transform]
                }
              }
              work_piece[['vars_to_transform']] <- vars_to_transform
            }
            # Send flag to load metadata
            if (load_file_metadata) {
              work_piece[['save_metadata_in']] <- paste0(metadata_folder, '/', metadata_file_counter)
            }
            work_pieces <- c(work_pieces, list(work_piece))
          }
        }
        j <- j + 1
      }
    }
  }
#print("N")
if (debug) {
print("-> WORK PIECES BUILT")
}

  # Calculate the progress %s that will be displayed and assign them to 
  # the appropriate work pieces.
  if (length(work_pieces) / num_procs >= 2 && !silent) {
    if (length(work_pieces) / num_procs < 10) {
      amount <- 100 / ceiling(length(work_pieces) / num_procs)
      reps <- ceiling(length(work_pieces) / num_procs)
    } else {
      amount <- 10
      reps <- 10
    }
    progress_steps <- rep(amount, reps)
    if (length(work_pieces) < (reps + 1)) {
      selected_pieces <- length(work_pieces)
      progress_steps <- c(sum(head(progress_steps, reps)),
                          tail(progress_steps, reps))
    } else {
      selected_pieces <- round(seq(1, length(work_pieces), 
                                   length.out = reps + 1))[-1]
    }
    progress_steps <- paste0(' + ', round(progress_steps, 2), '%')
    progress_message <- 'Progress: 0%'
  } else {
    progress_message <- ''
    selected_pieces <- NULL
  }
  piece_counter <- 1
  step_counter <- 1
  work_pieces <- lapply(work_pieces, 
    function (x) {
      if (piece_counter %in% selected_pieces) {
        wp <- c(x, list(progress_amount = progress_steps[step_counter]))
        step_counter <<- step_counter + 1
      } else {
        wp <- x
      }
      piece_counter <<- piece_counter + 1
      wp
    })
  if (!silent) {
    .message("Detected dimension sizes:")
    longest_dim_len <- max(sapply(names(final_dims), nchar))
    longest_size_len <- max(sapply(paste0(final_dims, ''), nchar))
    sapply(names(final_dims), 
      function(x) {
        message(paste0("*   ", paste(rep(' ', longest_dim_len - nchar(x)), collapse = ''), 
                       x, ": ", paste(rep(' ', longest_size_len - nchar(paste0(final_dims[x], ''))), collapse = ''), 
                       final_dims[x]))
      })
    bytes <- prod(c(final_dims, 8))
    dim_sizes <- paste(final_dims, collapse = ' x ')
    .message(paste("Total size of requested data:"))
    .message(paste(dim_sizes, " x 8 bytes =", 
                   format(structure(bytes, class = "object_size"), units = "auto")), 
                   indent = 2)
    .message("If the size of the requested data is close to or above the free shared RAM memory, R may crash.")
    .message("If the size of the requested data is close to or above the half of the free RAM memory, R may crash.")
    .message(paste0("Will now proceed to read and process ", length(work_pieces), " data files:"))
    if (length(work_pieces) < 30) {
      lapply(work_pieces, function (x) .message(x[['file_path']], indent = 2))
    } else {
      .message("The list of files is long. You can check it after .Load() finishes in the output '$Files'.", indent = 2, exdent = 5)
    }
  }

  # Build the cluster of processes that will do the work and dispatch work pieces.
  # The function .LoadDataFile is applied to each work piece. This function will
  # open the data file, regrid if needed, subset, apply the mask, 
  # compute and apply the weights if needed,
  # disable extreme values and store in the shared memory matrix.
#print("O")
  if (!silent) {
    .message("Loading... This may take several minutes...")
    if (progress_message != '') {
      .message(progress_message, appendLF = FALSE)
    }
  }
  if (num_procs == 1) {
    found_files <- lapply(work_pieces, .LoadDataFile, 
                          shared_matrix_pointer = shared_matrix_pointer,
                          file_data_reader = file_data_reader, 
                          synonims = synonims,
                          transform = transform, 
                          transform_params = transform_params,
                          silent = silent, debug = debug)
  } else {
    cluster <- makeCluster(num_procs, outfile = "")
    # Send the heavy work to the workers
    work_errors <- try({
      found_files <- clusterApplyLB(cluster, work_pieces, .LoadDataFile, 
                                    shared_matrix_pointer = shared_matrix_pointer,
                                    file_data_reader = file_data_reader,
                                    synonims = synonims,
                                    transform = transform, 
                                    transform_params = transform_params,
                                    silent = silent, debug = debug)
    })
    stopCluster(cluster)
  }

  if (!silent) {
    if (progress_message != '') {
      .message("\n", tag = '')
    }
  }
#print("P")
  data_array <- array(bigmemory::as.matrix(data_array), dim = final_dims)
  gc()

  # Load metadata and remove the metadata folder
  loaded_metadata_files <- list.files(metadata_folder)
  loaded_metadata <- lapply(paste0(metadata_folder, '/', loaded_metadata_files), readRDS)
  unlink(metadata_folder, recursive = TRUE)
  return_metadata <- vector('list', length = prod(dim(array_of_metadata_flags)[metadata_dims]))
  return_metadata[as.numeric(loaded_metadata_files)] <- loaded_metadata
  dim(return_metadata) <- dim(array_of_metadata_flags[metadata_dims])
  attr(data_array, 'variables') <- return_metadata

  failed_pieces <- work_pieces[which(unlist(found_files))]
  for (failed_piece in failed_pieces) {
    array_of_not_found_files <- do.call('[<-', 
      c(list(array_of_not_found_files), 
        as.list(failed_piece[['file_indices_in_array_of_files']]),
        list(value = TRUE)))
  }
  if (any(array_of_not_found_files)) {
    for (i in 1:prod(dim(array_of_files_to_load))) {
      if (is.na(array_of_not_found_files[i])) {
        array_of_files_to_load[i] <- NA
      } else {
        if (array_of_not_found_files[i]) {
          array_of_not_found_files[i] <- array_of_files_to_load[i]
          array_of_files_to_load[i] <- NA
        } else {
          array_of_not_found_files[i] <- NA
        }
      }
    }
  } else {
    array_of_not_found_files <- NULL
  }

  # Replace the vars and common vars by the transformed vars and common vars
  for (i in 1:length(dat)) {
    if (length(names(transformed_vars[[i]])) > 0) {
      picked_vars[[i]][names(transformed_vars[[i]])] <- transformed_vars[[i]]
    } else if (length(names(picked_vars_ordered[[i]])) > 0) {
      picked_vars[[i]][names(picked_vars_ordered[[i]])] <- picked_vars_ordered[[i]]
    }
  }
  if (length(names(transformed_common_vars)) > 0) {
    picked_common_vars[names(transformed_common_vars)] <- transformed_common_vars
  } else if (length(names(picked_common_vars_ordered)) > 0) {
    picked_common_vars[names(picked_common_vars_ordered)] <- picked_common_vars_ordered
  }
if (debug) {
print("-> THE TRANSFORMED VARS:")
print(str(transformed_vars))
print("-> THE PICKED VARS:")
print(str(picked_vars))
}
  if (!silent) {
    .message("Successfully retrieved data.")
  }

  file_selectors <- NULL
  for (i in 1:length(dat)) {
    file_selectors[[dat[[i]][['name']]]] <- dat[[i]][['selectors']][which(names(dat[[i]][['selectors']]) %in% found_file_dims[[i]])]
  }
  list(Data = data_array, 
       Variables = c(list(common = picked_common_vars), picked_vars),
       Files = array_of_files_to_load, 
       NotFoundFiles = array_of_not_found_files,
       FileSelectors = file_selectors)
}

# This function is the responsible for loading the data of each work
# piece.
.LoadDataFile <- function(work_piece, shared_matrix_pointer, 
                          file_data_reader, synonims,
                          transform, transform_params,
                          silent = FALSE, debug = FALSE) {
#  suppressPackageStartupMessages({library(bigmemory)})
### TODO: Specify dependencies as parameter
#  suppressPackageStartupMessages({library(ncdf4)})
  # Auxiliar function to convert array indices to lineal indices.
  # This function expects a numeric vector of single indices or a list of 
  # numeric vectors with multiple indices for each dimension, and a 
  # numeric vector of dimension sizes.
  .arrayIndices2VectorIndices <- function(indices, dims) {
    # Check indices
    if (!is.list(indices)) {
      if (is.numeric(indices)) {
        indices <- as.list(indices)
      } else {
        stop("Parameter 'indices' must be a numeric vector or a list of ",
             "numeric vectors.")
      }
    }
    sapply(indices, 
      function(x) {
        if (!is.numeric(x)) {
          stop("Parameter 'indices' must be a numeric vector or a list ",
               "of numeric vectors.")
        } else if (any(is.na(x) | is.nan(x) | is.infinite(x))) {
          stop("Parameter 'indices' must not contain NA/NaN/Inf values.")
        } else if (length(x) < 1) {
          stop("Parameter 'indices' must contain at least one index ",
               "for each dimension.")
        }
      })
  
    # Check dims
    if (!is.numeric(dims)) {
      stop("Parameter 'dims' must be a numeric vector.")
    } else if (any(is.na(dims) | is.nan(dims) | is.infinite(dims))) {
      stop("Parameter 'dims' must not contain NA/NaN/Inf values.")
    } else if (any(sapply(dims, length) != 1)) {
      stop("Parameter 'dims' must contain a single numeric element for ",
           "each dimension.")
    } else if (length(indices) != length(dims)) {
      stop("There must be as many dimension selectors in 'indices' as ",
           "dimensions in 'dims'.")
    }
  
    find_indices <- function(indices, dims) {
      if (max(indices[[1]]) > dims[1] || min(indices[[1]]) < 1) {
        stop("Provided indices out of range.")
      }
      if (length(dims) == 1) {
        indices[[1]]
      } else {
        found_indices <- find_indices(indices[-1], dims[-1])
        new_found_indices <- c()
        for (i in 1:length(indices[[1]])) {
          new_found_indices <- c(new_found_indices, (indices[[1]][i] - 1) * prod(dims[-1]) + found_indices)
        }
        new_found_indices
      }
    }
  
    indices <- rev(indices)
    dims <- rev(dims)
  
    find_indices(indices, dims)
  }

#print("1")
  store_indices <- as.list(work_piece[['store_position']])
  first_round_indices <- work_piece[['first_round_indices']]
  second_round_indices <- work_piece[['second_round_indices']]
#print("2")
  file_to_open <- work_piece[['file_path']]
  sub_array <- file_data_reader(file_to_open, NULL, 
                                work_piece[['file_selectors']],
                                first_round_indices, synonims)
if (debug) {
if (all(unlist(store_indices[1:6]) == 1)) {
print("-> LOADING A WORK PIECE")
print("-> STRUCTURE OF READ UNTRANSFORMED DATA:")
print(str(sub_array))
print("-> STRUCTURE OF VARIABLES TO TRANSFORM:")
print(str(work_piece[['vars_to_transform']]))
print("-> COMMON ARRAY DIMENSIONS:")
print(str(work_piece[['store_dims']]))
}
}
  if (!is.null(sub_array)) {
    # Apply data transformation once we have the data arrays.
    if (!is.null(transform)) {
if (debug) {
if (all(unlist(store_indices[1:6]) == 1)) {
print("-> PROCEEDING TO TRANSFORM ARRAY")
print("-> DIMENSIONS OF ARRAY RIGHT BEFORE TRANSFORMING:")
print(dim(sub_array))
}
}
      sub_array <- do.call(transform, c(list(data_array = sub_array,
                                             variables = work_piece[['vars_to_transform']],
                                             file_dims = names(work_piece[['file_selectors']])),
                                             transform_params))
if (debug) {
if (all(unlist(store_indices[1:6]) == 1)) {
print("-> STRUCTURE OF ARRAY AND VARIABLES RIGHT AFTER TRANSFORMING:")
print(str(sub_array))
print("-> DIMENSIONS OF ARRAY RIGHT AFTER TRANSFORMING:")
print(dim(sub_array$data_array))
}
}
      sub_array <- sub_array$data_array
      # Subset with second round of indices
      dims_to_crop <- which(!sapply(second_round_indices, is.null))
      if (length(dims_to_crop) > 0) {
        dimnames_to_crop <- names(second_round_indices)[dims_to_crop]
        sub_array <- Subset(sub_array, dimnames_to_crop, 
                            second_round_indices[dimnames_to_crop])
      }
if (debug) {
if (all(unlist(store_indices[1:6]) == 1)) {
print("-> STRUCTURE OF ARRAY AND VARIABLES RIGHT AFTER SUBSETTING WITH 2nd ROUND INDICES:")
print(str(sub_array))
}
}
    }

    metadata <- attr(sub_array, 'variables')

    store_indices <- lapply(names(store_indices), 
      function (x) {
        if (!(x %in% names(first_round_indices))) {
          store_indices[[x]]
        } else if (is.null(second_round_indices[[x]])) {
          1:dim(sub_array)[x]
        } else {
          if (is.numeric(second_round_indices[[x]])) {
            ## TODO: Review carefully this line. Inner indices are all 
            ## aligned to the left-most positions. If dataset A has longitudes
            ## 1, 2, 3, 4 but dataset B has only longitudes 3 and 4, then
            ## they will be stored as follows:
            ## 1, 2, 3, 4
            ## 3, 4, NA, NA
            ##x - min(x) + 1
            1:length(second_round_indices[[x]])
          } else {
            1:length(second_round_indices[[x]])
          }
        }
      })
if (debug) {
if (all(unlist(store_indices) == 1)) {
print("-> STRUCTURE OF FIRST ROUND INDICES FOR THIS WORK PIECE:")
print(str(first_round_indices))
print("-> STRUCTURE OF SECOND ROUND INDICES FOR THIS WORK PIECE:")
print(str(second_round_indices))
print("-> STRUCTURE OF STORE INDICES FOR THIS WORK PIECE:")
print(str(store_indices))
}
}
    matrix_indices <- .arrayIndices2VectorIndices(store_indices, work_piece[['store_dims']])
    data_array <- bigmemory::attach.big.matrix(shared_matrix_pointer)
    data_array[matrix_indices] <- as.vector(sub_array)
    rm(data_array)
    gc()

    if (!is.null(work_piece[['save_metadata_in']])) {
      saveRDS(metadata, file = work_piece[['save_metadata_in']])
    }
  }
  if (!is.null(work_piece[['progress_amount']]) && !silent) {
    message(work_piece[['progress_amount']], appendLF = FALSE)
  }
  is.null(sub_array)
}