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#' Get name of variable for a specific element of list environment
#'
#' @param x A list environment.
#'
#' @param name The name or index of element of interest.
#'
#' @param mustExist If `TRUE`, an error is generated if `name` does not exist.
#'
#' @param create If `TRUE`, element `name` is created if missing.
#'
#' @return The name of the underlying variable
#'
#' @aliases get_variable.listenv
#' @export
#' @keywords internal
get_variable <- function(...) UseMethod("get_variable")
#' @rdname get_variable
#' @export
get_variable.listenv <- function(x, name, mustExist = FALSE,
create = !mustExist, ...) {
if (is.character(name)) {
} else if (is.numeric(name)) {
} else {
stopf("Subscript must be a name or an index: %s", mode(name), call. = FALSE)
}
dim <- dim(x)
if (is.null(dim)) {
if (length(name) != 1L) {
stopf("Subscript must be a scalar: %s", length(name), call. = FALSE)
}
} else {
ndim <- length(dim)
if (length(name) != 1L && length(name) != ndim) {
stopf("Subscript must be a scalar or of equal length to the number of dimension (%d): %d", ndim, length(name), call. = FALSE) #nolint
}
## Map multi-dimensional index to scalar index
if (length(name) > 1L) {
stop_if_not(is.numeric(name))
idxs <- name
if (anyNA(idxs)) stop("Unknown (NA) index detected")
for (kk in seq_len(ndim)) {
if (idxs[kk] < 1 || idxs[kk] > dim[kk]) {
stopf("Index #%d out of range [1,%d]: %s", kk, dim[kk], idxs[kk])
}
}
bases <- rev(c(cumprod(dim[-ndim]), 1))
idx <- sum(bases * (idxs - 1)) + 1
name <- idx
}
}
map <- mapping(x)
## Existing variable?
var <- map[name]
if (length(var) == 1L && !is.na(var)) return(var)
if (mustExist) {
stopf("No such %s element: %s", sQuote(class(x)[1]), name)
}
## Create new variable
if (is.character(name)) {
var <- name
## Non-existing name?
if (!is.element(name, names(map))) {
map <- c(map, var)
names(map)[length(map)] <- var
}
} else if (is.numeric(name)) {
i <- name
## Expand map?
if (i > length(map)) {
extra <- rep(NA_character_, times = i - length(map))
map <- c(map, extra)
}
## Create internal variable
var <- new_variable(x, value = NULL, create = create)
map[i] <- var
}
## Update map?
if (create) mapping(x) <- map
var
}
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