Add filter/withFilter method to Parser

Complement map and flatMap when used in for comprehensions. This is
required when pattern matching is used on the result of the generators.

It is implemented through a new filterWithError method on ParseResult.

4 files changed, 37 insertions, 0 deletions

diff --git a/test/files/run/parserFilter.check b/test/files/run/parserFilter.check
new file mode 100644
index 0000000000..be04454426
--- /dev/null
+++ b/test/files/run/parserFilter.check
@@ -0,0 +1,9 @@
+[1.3] failure: Input doesn't match filter: false
+
+if false
+  ^
+[1.1] failure: Input doesn't match filter: not
+
+not true
+^
+[1.8] parsed: (if~true)
diff --git a/test/files/run/parserFilter.scala b/test/files/run/parserFilter.scala
new file mode 100644
index 0000000000..d007d441f4
--- /dev/null
+++ b/test/files/run/parserFilter.scala
@@ -0,0 +1,15 @@
+object Test extends scala.util.parsing.combinator.RegexParsers {
+    val keywords = Set("if", "false")
+    def word: Parser[String] = "\\w+".r
+
+    def keyword: Parser[String] = word filter (keywords.contains)
+    def ident: Parser[String] = word filter(!keywords.contains(_))
+
+    def test = keyword ~ ident
+
+    def main(args: Array[String]) {
+      println(parseAll(test, "if false"))
+      println(parseAll(test, "not true"))
+      println(parseAll(test, "if true"))
+    }
+}
diff --git a/test/files/run/parserForFilter.check b/test/files/run/parserForFilter.check
new file mode 100644
index 0000000000..a53c147719
--- /dev/null
+++ b/test/files/run/parserForFilter.check
@@ -0,0 +1 @@
+[1.13] parsed: (second,first)
diff --git a/test/files/run/parserForFilter.scala b/test/files/run/parserForFilter.scala
new file mode 100644
index 0000000000..1bc44f8033
--- /dev/null
+++ b/test/files/run/parserForFilter.scala
@@ -0,0 +1,12 @@
+object Test extends scala.util.parsing.combinator.RegexParsers {
+  def word: Parser[String] = "\\w+".r
+
+  def twoWords = for {
+    (a ~ b) <- word ~ word
+  } yield (b, a)
+
+  def main(args: Array[String]) {
+    println(parseAll(twoWords, "first second"))
+  }
+}
+