34 lines
1.1 KiB
Scala
34 lines
1.1 KiB
Scala
package examples.parsing
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import scala.util.parsing.combinator.{Parsers, ImplicitConversions, ~, mkTilde}
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import scala.util.parsing.input.CharArrayReader
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object listParser {
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abstract class Tree
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case class Id(s: String) extends Tree
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case class Num(n: Int) extends Tree
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case class Lst(elems: List[Tree]) extends Tree
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import Character.{isLetter, isLetterOrDigit, isDigit}
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def mkString(cs: List[Any]) = cs.mkString("")
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class ListParsers extends Parsers {
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type Elem = Char
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lazy val ident = rep1(elem("letter", isLetter), elem("letter or digit", isLetterOrDigit)) ^^ {cs => Id(mkString(cs))}
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lazy val number = chainl1(elem("digit", isDigit) ^^ (_ - '0'), success{(accum: Int, d: Int) => accum * 10 + d}) ^^ Num
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lazy val list = '(' ~> repsep(expr, ',') <~ ')' ^^ Lst
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lazy val expr: Parser[Tree] = list | ident | number
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}
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def main(args: Array[String]) {
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println(
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if (args.length == 1) {
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(new ListParsers).expr(new CharArrayReader(args(0).toCharArray()))
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}
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else
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"usage: scala examples.parsing.listParser <list-string>"
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)
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}
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}
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