R/utils.R

In r-lib/ansistrings: Manipulation of 'ANSI' colored strings

#' Safe sequence operator
#'
#' This is a safer version of [base::seq()]. In particular, it avoids
#' creating backwards sequences, unless the `by` parameter is
#' explicitly negative.
#'
#' \code{\%:\%} is the operator version of `myseq`.
#'
#' @param from Start of sequence.
#' @param to End of sequence.
#' @param by Step size. Can be negative, and then `to` must not be more
#'   than `from`.
#' @return An integer vector.
#'
#' @keywords internal

myseq <- function(from, to, by = 1) {
  stopifnot(by != 0)
  if (by > 0) {
    if (to < from) {
      integer()
    } else {
      seq(from, to, by = by)
    }
  } else {
    if (to > from) {
      integer()
    } else {
      seq(from, to, by = by)
    }
  }
}

#' @rdname myseq

`%:%` <- function(from, to) myseq(from, to)

str_insert_parallel <- function(str, pos, insert) {

  text_starts <- c(1, pos)
  text_ends   <- c(pos - 1, nchar(str))

  text_pieces <- substring(str, text_starts, text_ends)

  res <- character(length(text_pieces) + length(insert))
  res[myseq(1, length(res), by = 2)] <- text_pieces
  res[myseq(2, length(res) - 1, by = 2)] <- insert

  paste(res, collapse = "")
}