Split on sentence and other boundaries

NEWS.md

@@ -14,6 +14,9 @@
 * `str_replace()` and `str_replace_all()` now behave correctly when a
   replacement string contains `$`s, `\\\\1`, etc. (#83, @gagolews).
 
+* `boundary()` has a different default argument which works for splitting on
+   sentence boundaries (#58, @lmullen).
+
 # stringr 1.0.0
 
 * stringr is now powered by [stringi](https://github.com/Rexamine/stringi) 

R/modifiers.r

@@ -115,12 +115,18 @@ regex <- function(pattern, ignore_case = FALSE, multiline = FALSE,
 
 #' @param type Boundary type to detect.
 #' @param skip_word_none Ignore "words" that don't contain any characters
-#'   or numbers - i.e. punctuation.
+#'   or numbers - i.e. punctuation. Default \code{NA} will skip such "words"
+#'   only when splitting on \code{word} boundaries.
 #' @export
 #' @rdname modifiers
 boundary <- function(type = c("character", "line_break", "sentence", "word"),
-                    skip_word_none = TRUE, ...) {
+                    skip_word_none = NA, ...) {
   type <- match.arg(type)
+
+  if (identical(skip_word_none, NA)) {
+    skip_word_none <- type == "word"
+  }
+
   options <- stri_opts_brkiter(
     type = type,
     skip_word_none = skip_word_none,

tests/testthat/test-split.r

@@ -67,3 +67,16 @@ test_that("n sets exact number of splits in str_split_fixed", {
     equals(c("Subject", "Roger: his drinking problems")))
 
 })
+
+test_that("str_split can split sentences correctly", {
+  test <- "This is a sentence. Is this a sentence? Why, yes it is."
+
+  expect_that(
+    length(str_split(test, boundary("sentence"))[[1]]),
+    equals(3))
+  expect_that(
+    str_split(test, boundary("sentence")),
+    equals(list(c("This is a sentence. ", "Is this a sentence? ",
+                  "Why, yes it is."))))
+
+})