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Commit 7f86709

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Merge pull request #370 from ilya-klyuchnikov/phrase
2 parents 55a539d + 1e703fe commit 7f86709

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2 files changed

+53
-1
lines changed

2 files changed

+53
-1
lines changed

‎shared/src/main/scala/scala/util/parsing/combinator/PackratParsers.scala

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -101,7 +101,7 @@ trait PackratParsers extends Parsers {
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* Overridden to make sure any input passed to the argument parser
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* is wrapped in a `PackratReader`.
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*/
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override def phrase[T](p: Parser[T]) = {
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override def phrase[T](p: Parser[T]):PackratParser[T] = {
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val q = super.phrase(p)
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new PackratParser[T] {
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def apply(in: Input) = in match {

‎shared/src/test/scala/scala/util/parsing/combinator/PackratParsersTest.scala

Lines changed: 52 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -133,6 +133,35 @@ class PackratParsersTest {
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assertFailure("end of input", "a a a a b b b b c c c")
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}
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@Test
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def test4: Unit = {
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import grammars4._
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import grammars4.parser._
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def extractResult(r: ParseResult[Res]): Res = r match {
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case Success(a,_) => a
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case NoSuccess(a,_) => sys.error(a)
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case Failure(a, _) => sys.error(a)
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case Error(a, _) => sys.error(a)
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}
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def check(expected: Term, input: String, ctx: Ctx): Unit = {
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val parseResult = phraseTerm(new lexical.Scanner(input))
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val result = extractResult(parseResult)
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val term = result(ctx)
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assertEquals(expected, term)
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}
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check(Var(-1, 0), "x", Nil)
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check(Var(0, 3), "x", List("x", "y", "z"))
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check(Var(1, 3), "y", List("x", "y", "z"))
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check(Var(2, 3), "z", List("x", "y", "z"))
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check(App(Var(0, 2), Var(1, 2)), "x y", List("x", "y"))
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check(App(App(Var(0, 2), Var(1, 2)), Var(0, 2)), "x y x", List("x", "y"))
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check(App(App(Var(0, 2), Var(1, 2)), Var(0, 2)), "(x y) x", List("x", "y"))
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check(Abs(App(App(Var(0, 1), Var(0, 1)), Var(0, 1))), """\x. x x x""", List())
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}
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}
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private object grammars1 extends StandardTokenParsers with PackratParsers {
@@ -195,3 +224,26 @@ private object grammars3 extends StandardTokenParsers with PackratParsers {
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p~opt(repMany(p,q))~q ^^ {case x~Some(xs)~y => x::xs:::(y::Nil)}
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}
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private object grammars4 {
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// untyped lambda calculus with named vars -> de brujin indices conversion on the fly
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// Adapted from https://github.com/ilya-klyuchnikov/tapl-scala/blob/master/src/main/scala/tapl/untyped/parser.scala
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sealed trait Term
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case class Var(i: Int, cl: Int) extends Term
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case class Abs(t: Term) extends Term
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case class App(t1: Term, t2: Term) extends Term
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object parser extends StandardTokenParsers with PackratParsers {
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lexical.delimiters ++= List("(", ")", ".", "\\")
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type Res = Ctx => Term
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type Ctx = List[String]
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private val term: PackratParser[Res] = app | atom | abs
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private val atom: PackratParser[Res] = "(" ~> term <~ ")" | id
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private val id : PackratParser[Res] = ident ^^ { n => (c: Ctx) => Var(c.indexOf(n), c.length) }
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private val app : PackratParser[Res] = (app ~ atom) ^^ {case t1 ~ t2 => (c: Ctx) => App(t1(c), t2(c)) } | atom
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private val abs : PackratParser[Res] = "\\" ~> ident ~ ("." ~> term) ^^ {case v ~ t => (c: Ctx) => Abs(t(v::c))}
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val phraseTerm : PackratParser[Res] = phrase(term)
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}
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}

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