R/altrep_backend-trim.R

In charr: String Processing Reimagined for 'ALTREP' Strings

# Copied from stringi; stri_* renamed to ci_*.
# kate: default-dictionary en_US

## This file is part of the 'stringi' package for R.
## Copyright (c) 2013-2025, Marek Gagolewski <https://www.gagolewski.com/>
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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{ci_trim} is a convenience wrapper over \code{ci_trim_left}
# and \code{ci_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{ci_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{ci_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
# ci_trim_left('               aaa')
# ci_trim_right('r-project.org/', '\\P{P}')
# ci_trim_both(' Total of 23.5 bitcoins. ', '\\p{N}')
# ci_trim_both(' Total of 23.5 bitcoins. ', '\\P{N}', negate=TRUE)
#
# @aliases ci_trim
# @family search_replace
# @family search_charclass
# @rdname ci_trim
# @export
ci_trim_both <- function(str, pattern="\\P{Wspace}", negate=FALSE)
{
    .Call(C_ci_trim_both, str, pattern, negate)
}


# @rdname ci_trim
# @export
ci_trim_left <- function(str, pattern="\\P{Wspace}", negate=FALSE)
{
    .Call(C_ci_trim_left, str, pattern, negate)
}


# @rdname ci_trim
# @export
ci_trim_right <- function(str, pattern="\\P{Wspace}", negate=FALSE)
{
    .Call(C_ci_trim_right, str, pattern, negate)
}


# @rdname ci_trim
# @export
ci_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=ci_trim_both(str, pattern, negate),
        left=ci_trim_left(str, pattern, negate),
        right=ci_trim_right(str, pattern, negate)
    )
}