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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 ||| (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](def 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 = 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;
}
abstract class
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