#' Check for scalar argument
#'
#' This function checks for user's input is a scalar
#'
#' @details user's entry must meet the following criteria:
#' character,
#' length 1,
#' not NA,
#' non-zero length
#'
#' @param x character (1)
#'
#' @return boolean TRUE or FALSE
#'
#' @export
is_scalar_character <- function(x){
is.character(x) && length (x) == 1 && !is.na(x) && nzchar(x)
}
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