R/search_match_4.R

In stringi: Fast and Portable Character String Processing Facilities

# kate: default-dictionary en_US

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#' @title
#' Extract Regex Pattern Matches, Together with Capture Groups
#'
#' @description
#' These functions extract substrings in \code{str} that
#' match a given regex \code{pattern}. Additionally, they extract matches
#' to every \emph{capture group}, i.e., to all the sub-patterns given
#' in round parentheses.
#'
#' @details
#' Vectorized over \code{str} and \code{pattern} (with recycling
#' of the elements in the shorter vector if necessary). This allows to,
#' for instance, search for one pattern in each given string,
#' search for each pattern in one given string,
#' and search for the i-th pattern within the i-th string.
#'
#' If no pattern match is detected and \code{omit_no_match=FALSE},
#' then \code{NA}s are included in the resulting matrix (matrices), see Examples.
#'
#' \code{stri_match}, \code{stri_match_all}, \code{stri_match_first},
#' and \code{stri_match_last} are convenience functions.
#' They merely call \code{stri_match_*_regex} and are
#' provided for consistency with other string searching functions' wrappers,
#' see, among others, \code{\link{stri_extract}}.
#'
#' @param str character vector; strings to search in
#' @param pattern,regex character vector;
#'     search patterns; for more details refer to \link{stringi-search}
#' @param opts_regex a named list with \pkg{ICU} Regex settings,
#' see \code{\link{stri_opts_regex}}; \code{NULL}
#' for default settings
#' @param omit_no_match single logical value; if \code{FALSE},
#' then a row with missing values will indicate that there was no match;
#' \code{stri_match_all_*} only
#' @param cg_missing single string to be used if a capture group match
#' is unavailable
#' @param mode single string;
#' one of: \code{'first'} (the default), \code{'all'}, \code{'last'}
#' @param ... supplementary arguments passed to the underlying functions,
#' including additional settings for \code{opts_regex}
#'
#' @return
#' For \code{stri_match_all*},
#' a list of character matrices is returned. Each list element
#' represents the results of a different search scenario.
#'
#' For \code{stri_match_first*} and \code{stri_match_last*}
#' a character matrix is returned.
#' Each row corresponds to a different search result.
#'
#' The first matrix column gives the whole match. The second one corresponds to
#' the first capture group, the third -- the second capture group, and so on.
#'
#' If regular expressions feature a named capture group,
#' the matrix columns will be named accordingly.
#' However, for \code{stri_match_first*} and \code{stri_match_last*}
#' this will only be the case if there is a single pattern.
#'
#'
#' @examples
#' stri_match_all_regex('breakfast=eggs, lunch=pizza, dessert=icecream',
#'    '(\\w+)=(\\w+)')
#' stri_match_all_regex(c('breakfast=eggs', 'lunch=pizza', 'no food here'),
#'    '(\\w+)=(\\w+)')
#' stri_match_all_regex(c('breakfast=eggs;lunch=pizza',
#'    'breakfast=bacon;lunch=spaghetti', 'no food here'),
#'    '(\\w+)=(\\w+)')
#' stri_match_all_regex(c('breakfast=eggs;lunch=pizza',
#'    'breakfast=bacon;lunch=spaghetti', 'no food here'),
#'    '(?<when>\\w+)=(?<what>\\w+)')  # named capture groups
#' stri_match_first_regex(c('breakfast=eggs;lunch=pizza',
#'    'breakfast=bacon;lunch=spaghetti', 'no food here'),
#'    '(\\w+)=(\\w+)')
#' stri_match_last_regex(c('breakfast=eggs;lunch=pizza',
#'    'breakfast=bacon;lunch=spaghetti', 'no food here'),
#'    '(\\w+)=(\\w+)')
#'
#' stri_match_first_regex(c('abcd', ':abcd', ':abcd:'), '^(:)?([^:]*)(:)?$')
#' stri_match_first_regex(c('abcd', ':abcd', ':abcd:'), '^(:)?([^:]*)(:)?$', cg_missing='')
#'
#' # Match all the pattern of the form XYX, including overlapping matches:
#' stri_match_all_regex('ACAGAGACTTTAGATAGAGAAGA', '(?=(([ACGT])[ACGT]\\2))')[[1]][,2]
#' # Compare the above to:
#' stri_extract_all_regex('ACAGAGACTTTAGATAGAGAAGA', '([ACGT])[ACGT]\\1')
#'
#' @family search_extract
#' @export
#' @rdname stri_match
stri_match_all <- function(str, ..., regex)
{
    stri_match_all_regex(str, regex, ...)
}


#' @export
#' @rdname stri_match
stri_match_first <- function(str, ..., regex)
{
    stri_match_first_regex(str, regex, ...)
}


#' @export
#' @rdname stri_match
stri_match_last <- function(str, ..., regex)
{
    stri_match_last_regex(str, regex, ...)
}


#' @export
#' @rdname stri_match
stri_match <- function(str, ..., regex, mode = c("first", "all", "last"))
{
    # `first` is default for compatibility with stringr
    mode <- match.arg(mode)  # this is slow

    switch(mode,
        first = stri_match_first_regex(str, regex, ...),
        last = stri_match_last_regex(str, regex, ...),
        all = stri_match_all_regex(str, regex, ...))
}


#' @export
#' @rdname stri_match
stri_match_all_regex <- function(str, pattern,
    omit_no_match = FALSE, cg_missing = NA_character_,
    ..., opts_regex = NULL)
{
    if (!missing(...))
        opts_regex <- do.call(stri_opts_regex, as.list(c(opts_regex, ...)))
    .Call(C_stri_match_all_regex, str, pattern, omit_no_match, cg_missing, opts_regex)
}


#' @export
#' @rdname stri_match
stri_match_first_regex <- function(str, pattern, cg_missing = NA_character_, ...,
    opts_regex = NULL)
{
    if (!missing(...))
        opts_regex <- do.call(stri_opts_regex, as.list(c(opts_regex, ...)))
    .Call(C_stri_match_first_regex, str, pattern, cg_missing, opts_regex)
}


#' @export
#' @rdname stri_match
stri_match_last_regex <- function(str, pattern, cg_missing = NA_character_, ...,
    opts_regex = NULL)
{
    if (!missing(...))
        opts_regex <- do.call(stri_opts_regex, as.list(c(opts_regex, ...)))
    .Call(C_stri_match_last_regex, str, pattern, cg_missing, opts_regex)
}