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() } } } } trait 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)) } } trait 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 }