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package examples;
abstract class Parsers {
type intype;
trait Parser[a] {
type Result = Option[Pair[a, intype]];
def apply(in: intype): Result;
def filter(pred: a => boolean) = new Parser[a] {
def apply(in: intype): 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: intype): 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: intype): 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: intype): 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: intype): 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());
}
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;
}
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