1 files changed, 108 insertions, 0 deletions
diff --git a/docs/examples/Parsers.scala b/docs/examples/Parsers.scala
new file mode 100644
index 0000000000..10512ab2fd
--- /dev/null
+++ b/docs/examples/Parsers.scala
@@ -0,0 +1,108 @@
+package examples;
+
+abstract class Parsers {
+
+  type inputType;
+
+  trait Parser[a] {
+
+    type Result = Option[Pair[a, inputType]];
+
+    def apply(in: inputType): Result;
+
+    def filter(pred: a => boolean) = new Parser[a] {
+      def apply(in: inputType): Result = Parser.this.apply(in) match {
+        case None => None
+        case Some(Pair(x, in1)) => if (pred(x)) Some(Pair(x, in1)) else None
+      }
+    }
+
+    def map[b](f: a => b) = new Parser[b] {
+      def apply(in: inputType): Result = Parser.this.apply(in) match {
+        case None => None
+        case Some(Pair(x, in1)) => Some(Pair(f(x), in1))
+      }
+    }
+
+    def flatMap[b](f: a => Parser[b]) = new Parser[b] {
+      def apply(in: inputType): Result = Parser.this.apply(in) match {
+        case None => None
+        case Some(Pair(x, in1)) => f(x).apply(in1)
+      }
+    }
+
+    def ||| (p: => Parser[a]) = new Parser[a] {
+      def apply(in: inputType): Result = Parser.this.apply(in) match {
+	case None => p(in)
+	case s => s
+      }
+    }
+
+    def &&& [b](p: => Parser[b]): Parser[b] =
+      for (val _ <- this; val x <- p) yield x;
+  }
+
+  def succeed[a](x: a) = new Parser[a] {
+    def apply(in: inputType): Result = Some(Pair(x, in))
+  }
+
+  def rep[a](p: Parser[a]): Parser[List[a]] =
+    rep1(p) ||| succeed(List());
+
+  def rep1[a](p: Parser[a]): Parser[List[a]] =
+    for (val x <- p; val xs <- rep(p)) yield x :: xs;
+
+  def opt[a](p: Parser[a]): Parser[List[a]] =
+    (for (val x <- p) yield List(x)) ||| succeed(List());
+}
+
+class Tokenizer(in: Iterator[char], delimiters: String) extends Iterator[String] {
+
+  val EOI: char = 0;
+
+  def nextChar() =
+    if (in.hasNext) in.next else EOI;
+
+  private var ch = nextChar();
+
+  def isDelimiter(ch: Char) = {
+    var i = 0;
+    while (i < delimiters.length() && delimiters.charAt(i) != ch) { i = i + 1 }
+    i < delimiters.length()
+  }
+
+  def hasNext: boolean = ch != EOI;
+
+  private val buf = new StringBuffer;
+
+  def next: String = {
+    while (ch <= ' ' && ch != EOI) nextChar();
+    if (ch == EOI) ""
+    else {
+      if (isDelimiter(ch)) ch.toString()
+      else {
+        buf.setLength(0); buf append ch;
+	while (ch > ' ' && ch != EOI && !isDelimiter(ch)) {
+          buf append ch; nextChar();
+        }
+        buf.toString()
+      }
+    }
+  }
+}
+
+abstract class TokenParsers extends Parsers {
+  type inputType = Stream[String];
+  def nextToken() = new Parser[String] {
+    def apply(in: inputType): Result =
+      if (in.isEmpty) None else Some(Pair(in.head, in.tail));
+  }
+}
+
+abstract class CharParsers extends Parsers {
+  def any: Parser[char];
+  def chr(ch: char) =
+    for (val c <- any; c == ch) yield c;
+  def chr(p: char => boolean) =
+    for (val c <- any; p(c)) yield c;
+}