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author | Gilles Dubochet <gilles.dubochet@epfl.ch> | 2005-12-16 18:44:33 +0000 |
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committer | Gilles Dubochet <gilles.dubochet@epfl.ch> | 2005-12-16 18:44:33 +0000 |
commit | 53a3cc7b17f4cf97075b7e71720777fd84109696 (patch) | |
tree | 0cc784e0b47ea49cc151a136d19f20bfa8ee2197 /docs/examples/parsers2.scala | |
parent | df50e05006b43b007c2587549030d24b5c154398 (diff) | |
download | scala-53a3cc7b17f4cf97075b7e71720777fd84109696.tar.gz scala-53a3cc7b17f4cf97075b7e71720777fd84109696.tar.bz2 scala-53a3cc7b17f4cf97075b7e71720777fd84109696.zip |
Created proper 'docs' folder for new layout.
Diffstat (limited to 'docs/examples/parsers2.scala')
-rw-r--r-- | docs/examples/parsers2.scala | 63 |
1 files changed, 63 insertions, 0 deletions
diff --git a/docs/examples/parsers2.scala b/docs/examples/parsers2.scala new file mode 100644 index 0000000000..47fa8d0f2e --- /dev/null +++ b/docs/examples/parsers2.scala @@ -0,0 +1,63 @@ +package examples; + +object parsers2 { + + abstract class Tree{} + case class Id (s: String) extends Tree {} + case class Num(n: int) extends Tree {} + case class Lst(elems: List[Tree]) extends Tree {} + + abstract class ListParsers extends CharParsers { + + def ident: Parser[Tree] = + for ( + val c: char <- chr(Character.isLetter); + val cs: List[char] <- rep(chr(Character.isLetterOrDigit)) + ) yield Id((c :: cs).mkString("", "", "")); + + def number: Parser[Tree] = + for ( + val d: char <- chr(Character.isDigit); + val ds: List[char] <- rep(chr(Character.isDigit)) + ) yield Num(((d - '0') /: ds) ((x, digit) => x * 10 + digit - '0')); + + def list: Parser[Tree] = + for ( + val _ <- chr('('); + val es <- listElems ||| succeed(List()); + val _ <- chr(')') + ) yield Lst(es); + + def listElems: Parser[List[Tree]] = + for ( + val x <- expr; + val xs <- chr(',') &&& listElems ||| succeed(List()) + ) yield x :: xs; + + def expr: Parser[Tree] = + list ||| ident ||| number; + + } + + class ParseString(s: String) extends Parsers { + type inputType = int; + val input = 0; + def any = new Parser[char] { + def apply(in: int): Parser[char]#Result = + if (in < s.length()) Some(Pair(s charAt in, in + 1)) else None; + } + } + + def main(args: Array[String]): unit = + Console.println( + if (args.length == 1) { + val ps = new ListParsers with ParseString(args(0)); + ps.expr(ps.input) match { + case Some(Pair(list, _)) => Console.println("parsed: " + list); + case None => "nothing parsed" + } + } else "usage: scala examples.parsers2 <expr-string>" + ); + +} + |