R/trim.R

In stringi: Fast and Portable Character String Processing Facilities

# kate: default-dictionary en_US

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#' @title
#' Trim Characters from the Left and/or Right Side of a String
#'
#' @description
#' These functions may be used, e.g., to remove unnecessary
#' white-spaces from strings. Trimming ends at the first or
#' starts at the last \code{pattern} match.
#'
#' @details
#' Vectorized over \code{str} and \code{pattern}.
#'
#' \code{stri_trim} is a convenience wrapper over \code{stri_trim_left}
#' and \code{stri_trim_right}.
#'
#' Contrary to many other string processing libraries,
#' our trimming functions are universal. The class of characters
#' to be retained or trimmed can be adjusted.
#'
#' For replacing pattern matches with
#' an arbitrary replacement string, see \code{\link{stri_replace}}.
#'
#' Trimming can also be used where you would normally rely on
#' regular expressions. For instance, you may get
#' \code{'23.5'} out of \code{'total of 23.5 bitcoins'}.
#'
#' For trimming white-spaces, please note the difference
#' between Unicode binary property `\code{\\p\{Wspace\}}` (more universal)
#' and general character category `\code{\\p\{Z\}}`,
#' see \link{stringi-search-charclass}.
#'
#' @param str a character vector of strings to be trimmed
#' @param pattern a single pattern, specifying the class of characters
#'     (see \link{stringi-search-charclass}) to
#'     to be preserved (if \code{negate} is \code{FALSE}; default)
#'     or trimmed (otherwise)
#' @param side character [\code{stri_trim} only]; defaults to \code{'both'}
#' @param negate either \code{TRUE} or \code{FALSE}; see \code{pattern}
#'
#'
#' @return
#' All functions return a character vector.
#'
#'
#' @examples
#' stri_trim_left('               aaa')
#' stri_trim_right('r-project.org/', '\\P{P}')
#' stri_trim_both(' Total of 23.5 bitcoins. ', '\\p{N}')
#' stri_trim_both(' Total of 23.5 bitcoins. ', '\\P{N}', negate=TRUE)
#'
#' @aliases stri_trim
#' @family search_replace
#' @family search_charclass
#' @rdname stri_trim
#' @export
stri_trim_both <- function(str, pattern="\\P{Wspace}", negate=FALSE)
{
    .Call(C_stri_trim_both, str, pattern, negate)
}


#' @rdname stri_trim
#' @export
stri_trim_left <- function(str, pattern="\\P{Wspace}", negate=FALSE)
{
    .Call(C_stri_trim_left, str, pattern, negate)
}


#' @rdname stri_trim
#' @export
stri_trim_right <- function(str, pattern="\\P{Wspace}", negate=FALSE)
{
    .Call(C_stri_trim_right, str, pattern, negate)
}


#' @rdname stri_trim
#' @export
stri_trim <- function(str, side=c("both", "left", "right"), pattern="\\P{Wspace}", negate=FALSE)
{
    # `both` is default for compatibility with stringr
    side <- match.arg(side)  # this is slow

    switch(side,
        both=stri_trim_both(str, pattern, negate),
        left=stri_trim_left(str, pattern, negate),
        right=stri_trim_right(str, pattern, negate)
    )
}