PEG.js grammar: Make rules with operators more generic

spec/parser.spec.js

@@ -292,24 +292,30 @@ describe("PEG.js grammar parser", function() {
 
   /* Canonical PrefixedExpression is "!\"abcd\"". */
   it("parses PrefixedExpression", function() {
-    expect('start = $"abcd"?'   ).toParseAs(oneRuleGrammar(textOptionalLiteral));
-    expect('start = $\n"abcd"?' ).toParseAs(oneRuleGrammar(textOptionalLiteral));
-    expect('start = &"abcd"?'   ).toParseAs(oneRuleGrammar(simpleAndOptionalLiteral));
-    expect('start = &\n"abcd"?' ).toParseAs(oneRuleGrammar(simpleAndOptionalLiteral));
     expect('start = !"abcd"?'   ).toParseAs(oneRuleGrammar(simpleNotOptionalLiteral));
     expect('start = !\n"abcd"?' ).toParseAs(oneRuleGrammar(simpleNotOptionalLiteral));
     expect('start = "abcd"?'    ).toParseAs(oneRuleGrammar(optionalLiteral));
   });
 
+  /* Canonical PrefixedOperator is "!". */
+  it("parses PrefixedOperator", function() {
+    expect('start = $"abcd"?'   ).toParseAs(oneRuleGrammar(textOptionalLiteral));
+    expect('start = &"abcd"?'   ).toParseAs(oneRuleGrammar(simpleAndOptionalLiteral));
+    expect('start = !"abcd"?'   ).toParseAs(oneRuleGrammar(simpleNotOptionalLiteral));
+  });
+
   /* Canonical SuffixedExpression is "\"abcd\"?". */
   it("parses SuffixedExpression", function() {
     expect('start = "abcd"?'  ).toParseAs(oneRuleGrammar(optionalLiteral));
     expect('start = "abcd"\n?').toParseAs(oneRuleGrammar(optionalLiteral));
+    expect('start = "abcd"'   ).toParseAs(literalGrammar("abcd"));
+  });
+
+  /* Canonical SuffixedOperator is "?". */
+  it("parses SuffixedExpression", function() {
+    expect('start = "abcd"?'  ).toParseAs(oneRuleGrammar(optionalLiteral));
     expect('start = "abcd"*'  ).toParseAs(oneRuleGrammar(zeroOrMoreLiteral));
-    expect('start = "abcd"\n*').toParseAs(oneRuleGrammar(zeroOrMoreLiteral));
     expect('start = "abcd"+'  ).toParseAs(oneRuleGrammar(oneOrMoreLiteral));
-    expect('start = "abcd"\n+').toParseAs(oneRuleGrammar(oneOrMoreLiteral));
-    expect('start = "abcd"'   ).toParseAs(literalGrammar("abcd"));
   });
 
   /* Canonical PrimaryExpression is "\"abcd\"". */
@@ -331,12 +337,16 @@ describe("PEG.js grammar parser", function() {
 
   /* Canonical SemanticPredicateExpression is "\"abcd\"". */
   it("parses SemanticPredicateExpression", function() {
-    expect('start = &{ code }'  ).toParseAs(oneRuleGrammar(semanticAnd));
-    expect('start = &\n{ code }').toParseAs(oneRuleGrammar(semanticAnd));
     expect('start = !{ code }'  ).toParseAs(oneRuleGrammar(semanticNot));
     expect('start = !\n{ code }').toParseAs(oneRuleGrammar(semanticNot));
   });
 
+  /* Canonical SemanticPredicateOperator is "!". */
+  it("parses SemanticPredicateExpression", function() {
+    expect('start = &{ code }').toParseAs(oneRuleGrammar(semanticAnd));
+    expect('start = !{ code }').toParseAs(oneRuleGrammar(semanticNot));
+  });
+
   /* The SourceCharacter rule is not tested. */
 
   /* Canonical WhiteSpace is " ". */

src/parser.pegjs

@@ -12,6 +12,23 @@
  */
 
 {
+  var OPS_TO_PREFIXED_TYPES = {
+    "$": "text",
+    "&": "simple_and",
+    "!": "simple_not"
+  };
+
+  var OPS_TO_SUFFIXED_TYPES = {
+    "?": "optional",
+    "*": "zero_or_more",
+    "+": "one_or_more"
+  };
+
+  var OPS_TO_SEMANTIC_PREDICATE_TYPES = {
+    "&": "semantic_and",
+    "!": "semantic_not"
+  };
+
   function extractOptional(optional, index) {
     return optional ? optional[index] : null;
   }
@@ -101,47 +118,27 @@ LabeledExpression
   / PrefixedExpression
 
 PrefixedExpression
-  = "$" __ expression:SuffixedExpression {
-      return {
-        type:       "text",
-        expression: expression
-      };
-    }
-  / "&" __ expression:SuffixedExpression {
-      return {
-        type:       "simple_and",
-        expression: expression
-      };
-    }
-  / "!" __ expression:SuffixedExpression {
-      return {
-        type:       "simple_not",
-        expression: expression
-      };
+  = operator:PrefixedOperator __ expression:SuffixedExpression {
+      return { type: OPS_TO_PREFIXED_TYPES[operator], expression: expression };
     }
   / SuffixedExpression
 
+PrefixedOperator
+  = "$"
+  / "&"
+  / "!"
+
 SuffixedExpression
-  = expression:PrimaryExpression __ "?" {
-      return {
-        type:       "optional",
-        expression: expression
-      };
-    }
-  / expression:PrimaryExpression __ "*" {
-      return {
-        type:       "zero_or_more",
-        expression: expression
-      };
-    }
-  / expression:PrimaryExpression __ "+" {
-      return {
-        type:       "one_or_more",
-        expression: expression
-      };
+  = expression:PrimaryExpression __ operator:SuffixedOperator {
+      return { type: OPS_TO_SUFFIXED_TYPES[operator], expression: expression };
     }
   / PrimaryExpression
 
+SuffixedOperator
+  = "?"
+  / "*"
+  / "+"
+
 PrimaryExpression
   = LiteralMatcher
   / CharacterClassMatcher
@@ -156,8 +153,13 @@ RuleReferenceExpression
     }
 
 SemanticPredicateExpression
-  = "&" __ code:CodeBlock { return { type: "semantic_and", code: code }; }
-  / "!" __ code:CodeBlock { return { type: "semantic_not", code: code }; }
+  = operator:SemanticPredicateOperator __ code:CodeBlock {
+      return { type: OPS_TO_SEMANTIC_PREDICATE_TYPES[operator], code: code };
+    }
+
+SemanticPredicateOperator
+  = "&"
+  / "!"
 
 /* "Lexical" elements */