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#' Pad a string.
#'
#' Vectorised over \code{string}. All other inputs should be of length 1.
#'
#' @param string input character vector
#' @param width pad strings to this minimum width
#' @param side side on which padding character is added (left, right or both)
#' @param pad single padding character (default is a space)
#' @return character vector
#' @seealso \code{\link{str_trim}} to remove whitespace
#' @keywords character
#' @export
#' @examples
#' rbind(
#' str_pad("hadley", 30, "left"),
#' str_pad("hadley", 30, "right"),
#' str_pad("hadley", 30, "both")
#' )
#' # Longer strings are returned unchanged
#' str_pad("hadley", 3)
str_pad <- function(string, width, side = "left", pad = " ") {
string <- check_string(string)
stopifnot(length(width) == 1)
stopifnot(length(side) == 1)
stopifnot(length(pad) == 1)
if (str_length(pad) != 1) {
stop("pad must be single character single")
}
side <- match.arg(side, c("left", "right", "both"))
needed <- pmax(0, width - str_length(string))
left <- switch(side,
left = needed, right = 0, both = floor(needed / 2))
right <- switch(side,
left = 0, right = needed, both = ceiling(needed / 2))
# String duplication is slow, so only do the absolute necessary
lengths <- unique(c(left, right))
padding <- str_dup(pad, lengths)
str_c(padding[match(left, lengths)], string, padding[match(right, lengths)])
}
#' Trim whitespace from start and end of string.
#'
#' @param string input character vector
#' @param side side on which whitespace is removed (left, right or both)
#' @return character vector with leading and trailing whitespace removed
#' @keywords character
#' @export
#' @seealso \code{\link{str_pad}} to add whitespace
#' @examples
#' str_trim(" String with trailing and leading white space\t")
#' str_trim("\n\nString with trailing and leading white space\n\n")
str_trim <- function(string, side = "both") {
string <- check_string(string)
stopifnot(length(side) == 1)
side <- match.arg(side, c("left", "right", "both"))
pattern <- switch(side, left = "^\\s+", right = "\\s+$",
both = "^\\s+|\\s+$")
str_replace_all(string, pattern, "")
}
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