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#' Count the number of matches in a string.
#'
#' Vectorised over \code{string} and \code{pattern}, shorter is recycled to
#' same length as longest.
#'
#' @inheritParams str_detect
#' @keywords character
#' @return integer vector
#' @seealso
#' \code{\link{regexpr}} which this function wraps
#'
#' \code{\link{str_locate}}/\code{\link{str_locate_all}} to locate position
#' of matches
#'
#' @export
#' @examples
#' fruit <- c("apple", "banana", "pear", "pineapple")
#' str_count(fruit, "a")
#' str_count(fruit, "p")
#' str_count(fruit, "e")
#' str_count(fruit, c("a", "b", "p", "p"))
str_count <- function(string, pattern) {
if (length(string) == 0) return(character())
string <- check_string(string)
pattern <- check_pattern(pattern, string)
if (length(pattern) == 1) {
matches <- re_call("gregexpr", string, pattern)
} else {
matches <- unlist(re_mapply("gregexpr", string, pattern),
recursive = FALSE)
}
match_length <- function(x) {
len <- length(x)
if (len > 1) return(len)
if (identical(c(x), -1L)) 0L else 1L
}
vapply(matches, match_length, integer(1))
}
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