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#' Detect the presence or absence of a pattern in a string.
#'
#' Vectorised over \code{string} and \code{pattern}.
#'
#' @param string input vector. This must be an atomic vector, and will be
#' coerced to a character vector
#' @param pattern pattern to look for, as defined by a POSIX regular
#' expression. See the ``Extended Regular Expressions'' section of
#' \code{\link{regex}} for details. See \code{\link{fixed}},
#' \code{\link{ignore.case}} and \code{\link{perl}} for how to use other
#' types of matching: fixed, case insensitive and perl-compatible.
#' @return boolean vector
#' @seealso \code{\link{grepl}} which this function wraps
#' @keywords character
#' @export
#' @examples
#' fruit <- c("apple", "banana", "pear", "pinapple")
#' str_detect(fruit, "a")
#' str_detect(fruit, "^a")
#' str_detect(fruit, "a$")
#' str_detect(fruit, "b")
#' str_detect(fruit, "[aeiou]")
#'
#' # Also vectorised over pattern
#' str_detect("aecfg", letters)
str_detect <- function(string, pattern) {
string <- check_string(string)
pattern <- check_pattern(pattern, string)
if (length(pattern) == 1) {
results <- re_call("grepl", string, pattern)
} else {
results <- unlist(re_mapply("grepl", string, pattern))
}
is.na(results) <- is.na(string)
results
}
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