Implemented negative character classes (e.g. [^a-z]).

lib/metagrammar.pegjs

@@ -63,7 +63,7 @@ braced: "{" (braced / nonBraceCharacter)* "}" { return $1 + $2.join("") + $3; }
 
 nonBraceCharacters: nonBraceCharacter+ { return $1.join(""); }
 
-nonBraceCharacter: !("{" / "}") . { return $2; }
+nonBraceCharacter: [^{}] { return $1; }
 
 colon:    ":" __ { return $1; }
 slash:    "/" __ { return $1; }
@@ -125,8 +125,8 @@ singleQuotedCharacter
 
 simpleSingleQuotedCharacter: !("'" / "\\" / eolChar) . { return $2; }
 
-class "character class": "[" (classCharacterRange / classCharacter)* "]" __ {
+class "character class": "[" "^"? (classCharacterRange / classCharacter)* "]" __ {
-  return $2.join("");
+  return $2 + $3.join("");
 }
 
 classCharacterRange: bracketDelimitedCharacter "-" bracketDelimitedCharacter {

test/compiler-test.js

@@ -205,6 +205,19 @@ test("classes", function() {
   doesNotParse(nonEmptyClassParser, "");
   doesNotParse(nonEmptyClassParser, "ab");
 
+  var invertedEmptyClassParser = PEG.buildParser('start: []');
+  doesNotParse(invertedEmptyClassParser, "");
+  doesNotParse(invertedEmptyClassParser, "a");
+  doesNotParse(invertedEmptyClassParser, "ab");
+
+  var invertedNonEmptyClassParser = PEG.buildParser('start: [^ab-d]');
+  doesNotParse(invertedNonEmptyClassParser, "a", "a");
+  doesNotParse(invertedNonEmptyClassParser, "b", "b");
+  doesNotParse(invertedNonEmptyClassParser, "c", "c");
+  doesNotParse(invertedNonEmptyClassParser, "d", "d");
+  doesNotParse(invertedNonEmptyClassParser, "");
+  doesNotParse(invertedNonEmptyClassParser, "ab");
+
   /*
    * Test that the parsing position moves forward after successful parsing of
    * a class.

test/metagrammar-test.js

@@ -276,6 +276,7 @@ with (PEG.Grammar) {
   test("parses class", function() {
     grammarParserParses("start: []",          classGrammar(""));
     grammarParserParses("start: [a-d]",       classGrammar("a-d"));
+    grammarParserParses("start: [^a-d]",      classGrammar("^a-d"));
     grammarParserParses("start: [a]",         classGrammar("a"));
     grammarParserParses("start: [a-de-hi-l]", classGrammar("a-de-hi-l"));