R/locate.R

In re2r: RE2 Regular Expression

## This file is part of the 're2r' package for R.
## Copyright (C) 2016, Qin Wenfeng
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#' Locate the position of patterns in a string.
#'
#' Locate the position of patterns in a string.If the match is of length 0, (e.g. from a special match like $) end will be one character less than start. Vectorised over string and pattern.
#'
#' @param pattern a character vector or pre-compiled regular expressions
#' @param string a character vector
#' @param parallel use multithread
#' @param grain_size a minimum chunk size for tuning the behavior of parallel algorithms
#' @param ... further arguments passed to \code{\link{re2}}
#' @examples
#' re2_locate("yabba dabba doo", "d")
#'
#' fruit <- c("apple", "banana", "pear", "pineapple")
#' re2_locate(fruit, "$")
#' re2_locate(fruit, "a")
#' re2_locate(fruit, "e")
#' re2_locate(fruit, c("a", "b", "p", "p"))
#'
#' re2_locate_all(fruit, "a")
#' re2_locate_all(fruit, "e")
#' re2_locate_all(fruit, c("a", "b", "p", "p"))
#'
#' # Find location of every character
#' re2_locate_all(fruit, "\\P{M}")
#'
#' @return For \code{\link{re2_locate}}, an integer matrix. First column gives start postion of match, and second column gives end position. For \code{\link{re2_locate_all}} a list of integer matrices.
#'
#' @export
re2_locate = function(string, pattern,  parallel = FALSE, grain_size= 100000, ...) {

    if (is.character(pattern) || mode(pattern) == "logical") {
        pattern = re2(pattern, ...)
    }
    cpp_locate(stri_enc_toutf8(string), pattern, FALSE, parallel, grain_size)
}

#' @rdname re2_locate
#' @export
re2_locate_all = function(string, pattern,  parallel = FALSE, grain_size= 100000, ...) {

    if (is.character(pattern) || mode(pattern) == "logical") {
        pattern = re2(pattern, ...)
    }
    cpp_locate(stri_enc_toutf8(string), pattern, TRUE, parallel, grain_size)
}