BROKEN: non-associative operators are not yet working

Author: peteraldous

Diff for: shared/src/main/scala/scala/util/parsing/combinator/Parsers.scala

@@ -1107,8 +1107,12 @@ trait Parsers {
     private def expandLeft(lhs: Exp, input: Reader[Elem], minLevel: Int): Expansion = {
       binop(input) match {
         case Success(op, binInput) => {
-          val prec = precedence(op);
-          if (prec >= minLevel) {
+          val (prec, assoc) = opData(op);
+          val canExpand = assoc match {
+            case Associativity.Non => prec > minLevel
+            case _ => prec >= minLevel
+          };
+          if (canExpand) {
             primary(binInput) match {
               case Success(rhs, next) => {
                 expandRight(rhs, next, prec) match {

Diff for: shared/src/test/scala/scala/util/parsing/combinator/PrecedenceParserTest.scala

@@ -23,6 +23,12 @@ class PrecedenceParsersTest {
   object Divide extends Op {
     override def toString = "/"
   }
+  object LT extends Op {
+    override def toString = "<"
+  }
+  object GT extends Op {
+    override def toString = ">"
+  }
   object Equals extends Op {
     override def toString = "="
   }
@@ -39,9 +45,18 @@ class PrecedenceParsersTest {
     val prec = List(
       (Associativity.Left, List(Mult, Divide)),
       (Associativity.Left, List(Plus, Minus)),
+      (Associativity.Non, List(LT, GT)),
       (Associativity.Right, List(Equals)))
     def integer: Parser[Leaf] = "[0-9]+".r ^^ { (s: String) => Leaf(s.toInt) }
-    def binop: Parser[Op] = "+" ^^^ Plus | "-" ^^^ Minus | "*" ^^^ Mult | "/" ^^^ Divide | "=" ^^^ Equals
+    def binop: Parser[Op] = {
+      "+" ^^^ Plus |
+      "-" ^^^ Minus |
+      "*" ^^^ Mult |
+      "/" ^^^ Divide |
+      "<" ^^^ LT |
+      ">" ^^^ GT |
+      "=" ^^^ Equals
+    }
     def token: Parser[Token] = integer | binop
     def expression = new PrecedenceParser(integer, binop, prec, Binop.apply)
   }
@@ -73,6 +88,11 @@ class PrecedenceParsersTest {
     }
   }
 
+  @Test
+  def testNonAssoc(): Unit = {
+    testExp(Binop(Leaf(1), LT, Leaf(2)), "1 < 2 < 3", List[Token](LT, Leaf(3)));
+  }
+
   @Test
   def testGracefulEnd(): Unit = {
     testExp(Leaf(4), "4 +", List[Token](Plus));