diff --git a/README.md b/README.md
index 1549129..6d15897 100644
--- a/README.md
+++ b/README.md
@@ -291,7 +291,7 @@ expression as many times as possible.
 #### *expression* ?
 
 Try to match the expression. If the match succeeds, return its match result,
-otherwise return an empty string.
+otherwise return `null`.
 
 #### & *expression*
 
diff --git a/examples/css.pegjs b/examples/css.pegjs
index 7dc6c25..940d2ed 100644
--- a/examples/css.pegjs
+++ b/examples/css.pegjs
@@ -33,7 +33,7 @@ stylesheet
 
       return {
         type:    "stylesheet",
-        charset: charset !== "" ? charset[1] : null,
+        charset: charset !== null ? charset[1] : null,
         imports: importsConverted,
         rules:   rulesConverted
       };
@@ -44,7 +44,7 @@ import
       return {
         type:  "import_rule",
         href:  href,
-        media: media !== "" ? media : []
+        media: media !== null ? media : []
       };
     }
 
@@ -75,16 +75,16 @@ page
     declarationsHead:declaration?
     declarationsTail:(";" S* declaration?)*
     "}" S* {
-      var declarations = declarationsHead !== "" ? [declarationsHead] : [];
+      var declarations = declarationsHead !== null ? [declarationsHead] : [];
       for (var i = 0; i < declarationsTail.length; i++) {
-        if (declarationsTail[i][2] !== "") {
+        if (declarationsTail[i][2] !== null) {
           declarations.push(declarationsTail[i][2]);
         }
       }
 
       return {
         type:         "page_rule",
-        qualifier:    qualifier !== "" ? qualifier : null,
+        qualifier:    qualifier,
         declarations: declarations
       };
     }
@@ -119,9 +119,9 @@ ruleset
         selectors.push(selectorsTail[i][2]);
       }
 
-      var declarations = declarationsHead !== "" ? [declarationsHead] : [];
+      var declarations = declarationsHead !== null ? [declarationsHead] : [];
       for (i = 0; i < declarationsTail.length; i++) {
-        if (declarationsTail[i][2] !== "") {
+        if (declarationsTail[i][2] !== null) {
           declarations.push(declarationsTail[i][2]);
         }
       }
@@ -196,8 +196,8 @@ attrib
       return {
         type:      "attribute_selector",
         attribute: attribute,
-        operator:  operatorAndValue !== "" ? operatorAndValue[0] : null,
-        value:     operatorAndValue !== "" ? operatorAndValue[2] : null
+        operator:  operatorAndValue !== null ? operatorAndValue[0] : null,
+        value:     operatorAndValue !== null ? operatorAndValue[2] : null
       };
     }
 
@@ -208,7 +208,7 @@ pseudo
           return {
             type:   "function",
             name:   name,
-            params: params !== "" ? [params[0]] : []
+            params: params !== null ? [params[0]] : []
           };
         }
       / IDENT
@@ -230,7 +230,7 @@ declaration
         type:       "declaration",
         property:   property,
         expression: expression,
-        important:  important !== "" ? true : false
+        important:  important !== null ? true : false
       };
     }
 
@@ -262,7 +262,12 @@ term
       / FREQ S*
       / PERCENTAGE S*
       / NUMBER S*
-    )               { return { type: "value",  value: operator + value[0] }; }
+    ) {
+      return {
+        type: "value",
+        value: (operator !== null ? operator : "") + value[0]
+      };
+    }
   / value:URI S*    { return { type: "uri",    value: value               }; }
   / function
   / hexcolor
@@ -331,7 +336,7 @@ comment
 
 ident
   = dash:"-"? nmstart:nmstart nmchars:nmchar* {
-      return dash + nmstart + nmchars.join("");
+      return (dash !== null ? dash : "") + nmstart + nmchars.join("");
     }
 
 name
diff --git a/examples/javascript.pegjs b/examples/javascript.pegjs
index 370ee25..13206ad 100644
--- a/examples/javascript.pegjs
+++ b/examples/javascript.pegjs
@@ -478,25 +478,25 @@ ArrayLiteral
   = "[" __ elision:(Elision __)? "]" {
       return {
         type:     "ArrayLiteral",
-        elements: elision !== "" ? elision[0] : []
+        elements: elision !== null ? elision[0] : []
       };
     }
   / "[" __ elements:ElementList __ elision:("," __ (Elision __)?)? "]" {
       return {
         type:     "ArrayLiteral",
-        elements: elements.concat(elision !== "" && elision[2] !== "" ? elision[2][0] : [])
+        elements: elements.concat(elision !== null && elision[2] !== null ? elision[2][0] : [])
       };
     }
 
 ElementList
   = head:(
       elision:(Elision __)? element:AssignmentExpression {
-        return (elision !== "" ? elision[0] : []).concat(element);
+        return (elision !== null ? elision[0] : []).concat(element);
       }
     )
     tail:(
       __ "," __ elision:(Elision __)? element:AssignmentExpression {
-        return (elision !== "" ? elision[0] : []).concat(element);
+        return (elision !== null ? elision[0] : []).concat(element);
       }
     )* {
       var result = head;
@@ -519,7 +519,7 @@ ObjectLiteral
   = "{" __ properties:(PropertyNameAndValueList __ ("," __)?)? "}" {
       return {
         type:       "ObjectLiteral",
-        properties: properties !== "" ? properties[0] : []
+        properties: properties !== null ? properties[0] : []
       };
     }
 
@@ -663,7 +663,7 @@ CallExpression
 
 Arguments
   = "(" __ args:ArgumentList? __ ")" {
-    return args !== "" ? args : [];
+    return args !== null ? args : [];
   }
 
 ArgumentList
@@ -1143,7 +1143,7 @@ Block
   = "{" __ statements:(StatementList __)? "}" {
       return {
         type:       "Block",
-        statements: statements !== "" ? statements[0] : []
+        statements: statements !== null ? statements[0] : []
       };
     }
 
@@ -1187,7 +1187,7 @@ VariableDeclaration
       return {
         type:  "VariableDeclaration",
         name:  name,
-        value: value !== "" ? value[1] : null
+        value: value !== null ? value[1] : null
       };
     }
 
@@ -1196,7 +1196,7 @@ VariableDeclarationNoIn
       return {
         type:  "VariableDeclaration",
         name:  name,
-        value: value !== "" ? value[1] : null
+        value: value !== null ? value[1] : null
       };
     }
 
@@ -1221,7 +1221,7 @@ IfStatement
         type:          "IfStatement",
         condition:     condition,
         ifStatement:   ifStatement,
-        elseStatement: elseStatement !== "" ? elseStatement[3] : null
+        elseStatement: elseStatement !== null ? elseStatement[3] : null
       };
     }
 
@@ -1272,9 +1272,9 @@ ForStatement
     {
       return {
         type:        "ForStatement",
-        initializer: initializer !== "" ? initializer : null,
-        test:        test !== "" ? test : null,
-        counter:     counter !== "" ? counter : null,
+        initializer: initializer,
+        test:        test,
+        counter:     counter,
         statement:   statement
       };
     }
@@ -1358,10 +1358,10 @@ CaseBlock
     before:CaseClauses?
     defaultAndAfter:(__ DefaultClause __ CaseClauses?)? __
     "}" {
-      var before = before !== "" ? before : [];
-      if (defaultAndAfter !== "") {
+      var before = before !== null ? before : [];
+      if (defaultAndAfter !== null) {
         var defaultClause = defaultAndAfter[1];
-        var clausesAfter = defaultAndAfter[3] !== ""
+        var clausesAfter = defaultAndAfter[3] !== null
           ? defaultAndAfter[3]
           : [];
       } else {
@@ -1386,7 +1386,7 @@ CaseClause
       return {
         type:       "CaseClause",
         selector:   selector,
-        statements: statements !== "" ? statements[1] : []
+        statements: statements !== null ? statements[1] : []
       };
     }
 
@@ -1394,7 +1394,7 @@ DefaultClause
   = DefaultToken __ ":" statements:(__ StatementList)? {
       return {
         type:       "DefaultClause",
-        statements: statements !== "" ? statements[1] : []
+        statements: statements !== null ? statements[1] : []
       };
     }
 
@@ -1470,7 +1470,7 @@ FunctionDeclaration
       return {
         type:     "Function",
         name:     name,
-        params:   params !== "" ? params : [],
+        params:   params !== null ? params : [],
         elements: elements
       };
     }
@@ -1481,8 +1481,8 @@ FunctionExpression
     "{" __ elements:FunctionBody __ "}" {
       return {
         type:     "Function",
-        name:     name !== "" ? name : null,
-        params:   params !== "" ? params : [],
+        name:     name,
+        params:   params !== null ? params : [],
         elements: elements
       };
     }
@@ -1497,13 +1497,13 @@ FormalParameterList
     }
 
 FunctionBody
-  = elements:SourceElements? { return elements !== "" ? elements : []; }
+  = elements:SourceElements? { return elements !== null ? elements : []; }
 
 Program
   = elements:SourceElements? {
       return {
         type:     "Program",
-        elements: elements !== "" ? elements : []
+        elements: elements !== null ? elements : []
       };
     }
 
diff --git a/lib/compiler/passes/generate-bytecode.js b/lib/compiler/passes/generate-bytecode.js
index e9d95cd..9709f9e 100644
--- a/lib/compiler/passes/generate-bytecode.js
+++ b/lib/compiler/passes/generate-bytecode.js
@@ -466,7 +466,7 @@ module.exports = function(ast, options) {
     },
 
     optional: function(node, context) {
-      var emptyStringIndex = addConst('""');
+      var nullIndex = addConst('null');
 
       return buildSequence(
         generate(node.expression, {
@@ -476,7 +476,7 @@ module.exports = function(ast, options) {
         }),
         buildCondition(
           [op.IF_ERROR],
-          buildSequence([op.POP], [op.PUSH, emptyStringIndex]),
+          buildSequence([op.POP], [op.PUSH, nullIndex]),
           []
         )
       );
diff --git a/lib/parser.js b/lib/parser.js
index ded3551..e10921e 100644
--- a/lib/parser.js
+++ b/lib/parser.js
@@ -79,12 +79,12 @@ module.exports = (function() {
         peg$startRuleFunction  = peg$parsegrammar,
 
         peg$c0 = peg$FAILED,
-        peg$c1 = "",
+        peg$c1 = null,
         peg$c2 = [],
         peg$c3 = function(initializer, rules) {
               return {
                 type:        "grammar",
-                initializer: initializer !== "" ? initializer : null,
+                initializer: initializer,
                 rules:       rules
               };
             },
@@ -98,7 +98,7 @@ module.exports = (function() {
               return {
                 type:        "rule",
                 name:        name,
-                expression:  displayName !== ""
+                expression:  displayName !== null
                   ? {
                       type:       "named",
                       name:       displayName,
@@ -197,100 +197,101 @@ module.exports = (function() {
                 expression: expression
               };
             },
-        peg$c18 = function(name) {
+        peg$c18 = "",
+        peg$c19 = function(name) {
               return {
                 type: "rule_ref",
                 name: name
               };
             },
-        peg$c19 = function() { return { type: "any" }; },
-        peg$c20 = function(expression) { return expression; },
-        peg$c21 = { type: "other", description: "action" },
-        peg$c22 = function(braced) { return braced.substr(1, braced.length - 2); },
-        peg$c23 = "{",
-        peg$c24 = { type: "literal", value: "{", description: "\"{\"" },
-        peg$c25 = "}",
-        peg$c26 = { type: "literal", value: "}", description: "\"}\"" },
-        peg$c27 = /^[^{}]/,
-        peg$c28 = { type: "class", value: "[^{}]", description: "[^{}]" },
-        peg$c29 = "=",
-        peg$c30 = { type: "literal", value: "=", description: "\"=\"" },
-        peg$c31 = function() { return "="; },
-        peg$c32 = ":",
-        peg$c33 = { type: "literal", value: ":", description: "\":\"" },
-        peg$c34 = function() { return ":"; },
-        peg$c35 = ";",
-        peg$c36 = { type: "literal", value: ";", description: "\";\"" },
-        peg$c37 = function() { return ";"; },
-        peg$c38 = "/",
-        peg$c39 = { type: "literal", value: "/", description: "\"/\"" },
-        peg$c40 = function() { return "/"; },
-        peg$c41 = "&",
-        peg$c42 = { type: "literal", value: "&", description: "\"&\"" },
-        peg$c43 = function() { return "&"; },
-        peg$c44 = "!",
-        peg$c45 = { type: "literal", value: "!", description: "\"!\"" },
-        peg$c46 = function() { return "!"; },
-        peg$c47 = "$",
-        peg$c48 = { type: "literal", value: "$", description: "\"$\"" },
-        peg$c49 = function() { return "$"; },
-        peg$c50 = "?",
-        peg$c51 = { type: "literal", value: "?", description: "\"?\"" },
-        peg$c52 = function() { return "?"; },
-        peg$c53 = "*",
-        peg$c54 = { type: "literal", value: "*", description: "\"*\"" },
-        peg$c55 = function() { return "*"; },
-        peg$c56 = "+",
-        peg$c57 = { type: "literal", value: "+", description: "\"+\"" },
-        peg$c58 = function() { return "+"; },
-        peg$c59 = "(",
-        peg$c60 = { type: "literal", value: "(", description: "\"(\"" },
-        peg$c61 = function() { return "("; },
-        peg$c62 = ")",
-        peg$c63 = { type: "literal", value: ")", description: "\")\"" },
-        peg$c64 = function() { return ")"; },
-        peg$c65 = ".",
-        peg$c66 = { type: "literal", value: ".", description: "\".\"" },
-        peg$c67 = function() { return "."; },
-        peg$c68 = { type: "other", description: "identifier" },
-        peg$c69 = "_",
-        peg$c70 = { type: "literal", value: "_", description: "\"_\"" },
-        peg$c71 = function(chars) { return chars; },
-        peg$c72 = { type: "other", description: "literal" },
-        peg$c73 = "i",
-        peg$c74 = { type: "literal", value: "i", description: "\"i\"" },
-        peg$c75 = function(value, flags) {
+        peg$c20 = function() { return { type: "any" }; },
+        peg$c21 = function(expression) { return expression; },
+        peg$c22 = { type: "other", description: "action" },
+        peg$c23 = function(braced) { return braced.substr(1, braced.length - 2); },
+        peg$c24 = "{",
+        peg$c25 = { type: "literal", value: "{", description: "\"{\"" },
+        peg$c26 = "}",
+        peg$c27 = { type: "literal", value: "}", description: "\"}\"" },
+        peg$c28 = /^[^{}]/,
+        peg$c29 = { type: "class", value: "[^{}]", description: "[^{}]" },
+        peg$c30 = "=",
+        peg$c31 = { type: "literal", value: "=", description: "\"=\"" },
+        peg$c32 = function() { return "="; },
+        peg$c33 = ":",
+        peg$c34 = { type: "literal", value: ":", description: "\":\"" },
+        peg$c35 = function() { return ":"; },
+        peg$c36 = ";",
+        peg$c37 = { type: "literal", value: ";", description: "\";\"" },
+        peg$c38 = function() { return ";"; },
+        peg$c39 = "/",
+        peg$c40 = { type: "literal", value: "/", description: "\"/\"" },
+        peg$c41 = function() { return "/"; },
+        peg$c42 = "&",
+        peg$c43 = { type: "literal", value: "&", description: "\"&\"" },
+        peg$c44 = function() { return "&"; },
+        peg$c45 = "!",
+        peg$c46 = { type: "literal", value: "!", description: "\"!\"" },
+        peg$c47 = function() { return "!"; },
+        peg$c48 = "$",
+        peg$c49 = { type: "literal", value: "$", description: "\"$\"" },
+        peg$c50 = function() { return "$"; },
+        peg$c51 = "?",
+        peg$c52 = { type: "literal", value: "?", description: "\"?\"" },
+        peg$c53 = function() { return "?"; },
+        peg$c54 = "*",
+        peg$c55 = { type: "literal", value: "*", description: "\"*\"" },
+        peg$c56 = function() { return "*"; },
+        peg$c57 = "+",
+        peg$c58 = { type: "literal", value: "+", description: "\"+\"" },
+        peg$c59 = function() { return "+"; },
+        peg$c60 = "(",
+        peg$c61 = { type: "literal", value: "(", description: "\"(\"" },
+        peg$c62 = function() { return "("; },
+        peg$c63 = ")",
+        peg$c64 = { type: "literal", value: ")", description: "\")\"" },
+        peg$c65 = function() { return ")"; },
+        peg$c66 = ".",
+        peg$c67 = { type: "literal", value: ".", description: "\".\"" },
+        peg$c68 = function() { return "."; },
+        peg$c69 = { type: "other", description: "identifier" },
+        peg$c70 = "_",
+        peg$c71 = { type: "literal", value: "_", description: "\"_\"" },
+        peg$c72 = function(chars) { return chars; },
+        peg$c73 = { type: "other", description: "literal" },
+        peg$c74 = "i",
+        peg$c75 = { type: "literal", value: "i", description: "\"i\"" },
+        peg$c76 = function(value, flags) {
               return {
                 type:       "literal",
                 value:      value,
                 ignoreCase: flags === "i"
               };
             },
-        peg$c76 = { type: "other", description: "string" },
-        peg$c77 = function(string) { return string; },
-        peg$c78 = "\"",
-        peg$c79 = { type: "literal", value: "\"", description: "\"\\\"\"" },
-        peg$c80 = function(chars) { return chars.join(""); },
-        peg$c81 = "\\",
-        peg$c82 = { type: "literal", value: "\\", description: "\"\\\\\"" },
-        peg$c83 = { type: "any", description: "any character" },
-        peg$c84 = function(char_) { return char_; },
-        peg$c85 = "'",
-        peg$c86 = { type: "literal", value: "'", description: "\"'\"" },
-        peg$c87 = { type: "other", description: "character class" },
-        peg$c88 = "[",
-        peg$c89 = { type: "literal", value: "[", description: "\"[\"" },
-        peg$c90 = "^",
-        peg$c91 = { type: "literal", value: "^", description: "\"^\"" },
-        peg$c92 = "]",
-        peg$c93 = { type: "literal", value: "]", description: "\"]\"" },
-        peg$c94 = function(inverted, parts, flags) {
+        peg$c77 = { type: "other", description: "string" },
+        peg$c78 = function(string) { return string; },
+        peg$c79 = "\"",
+        peg$c80 = { type: "literal", value: "\"", description: "\"\\\"\"" },
+        peg$c81 = function(chars) { return chars.join(""); },
+        peg$c82 = "\\",
+        peg$c83 = { type: "literal", value: "\\", description: "\"\\\\\"" },
+        peg$c84 = { type: "any", description: "any character" },
+        peg$c85 = function(char_) { return char_; },
+        peg$c86 = "'",
+        peg$c87 = { type: "literal", value: "'", description: "\"'\"" },
+        peg$c88 = { type: "other", description: "character class" },
+        peg$c89 = "[",
+        peg$c90 = { type: "literal", value: "[", description: "\"[\"" },
+        peg$c91 = "^",
+        peg$c92 = { type: "literal", value: "^", description: "\"^\"" },
+        peg$c93 = "]",
+        peg$c94 = { type: "literal", value: "]", description: "\"]\"" },
+        peg$c95 = function(inverted, parts, flags) {
               var partsConverted = utils.map(parts, function(part) { return part.data; });
               var rawText = "["
-                + inverted
+                + (inverted !== null ? inverted : "")
                 + utils.map(parts, function(part) { return part.rawText; }).join("")
                 + "]"
-                + flags;
+                + (flags !== null ? flags : "");
 
               return {
                 type:       "class",
@@ -301,9 +302,9 @@ module.exports = (function() {
                 ignoreCase: flags === "i"
               };
             },
-        peg$c95 = "-",
-        peg$c96 = { type: "literal", value: "-", description: "\"-\"" },
-        peg$c97 = function(begin, end) {
+        peg$c96 = "-",
+        peg$c97 = { type: "literal", value: "-", description: "\"-\"" },
+        peg$c98 = function(begin, end) {
               if (begin.data.charCodeAt(0) > end.data.charCodeAt(0)) {
                 throw new this.SyntaxError(
                   "Invalid character range: " + begin.rawText + "-" + end.rawText + "."
@@ -316,18 +317,18 @@ module.exports = (function() {
                 rawText: begin.rawText + "-" + end.rawText
               };
             },
-        peg$c98 = function(char_) {
+        peg$c99 = function(char_) {
               return {
                 data:    char_,
                 // FIXME: Get the raw text from the input directly.
                 rawText: utils.quoteForRegexpClass(char_)
               };
             },
-        peg$c99 = "x",
-        peg$c100 = { type: "literal", value: "x", description: "\"x\"" },
-        peg$c101 = "u",
-        peg$c102 = { type: "literal", value: "u", description: "\"u\"" },
-        peg$c103 = function(char_) {
+        peg$c100 = "x",
+        peg$c101 = { type: "literal", value: "x", description: "\"x\"" },
+        peg$c102 = "u",
+        peg$c103 = { type: "literal", value: "u", description: "\"u\"" },
+        peg$c104 = function(char_) {
               return char_
                 .replace("b", "\b")
                 .replace("f", "\f")
@@ -336,48 +337,48 @@ module.exports = (function() {
                 .replace("t", "\t")
                 .replace("v", "\x0B"); // IE does not recognize "\v".
             },
-        peg$c104 = "\\0",
-        peg$c105 = { type: "literal", value: "\\0", description: "\"\\\\0\"" },
-        peg$c106 = function() { return "\x00"; },
-        peg$c107 = "\\x",
-        peg$c108 = { type: "literal", value: "\\x", description: "\"\\\\x\"" },
-        peg$c109 = function(digits) {
+        peg$c105 = "\\0",
+        peg$c106 = { type: "literal", value: "\\0", description: "\"\\\\0\"" },
+        peg$c107 = function() { return "\x00"; },
+        peg$c108 = "\\x",
+        peg$c109 = { type: "literal", value: "\\x", description: "\"\\\\x\"" },
+        peg$c110 = function(digits) {
               return String.fromCharCode(parseInt(digits, 16));
             },
-        peg$c110 = "\\u",
-        peg$c111 = { type: "literal", value: "\\u", description: "\"\\\\u\"" },
-        peg$c112 = function(eol) { return eol; },
-        peg$c113 = /^[0-9]/,
-        peg$c114 = { type: "class", value: "[0-9]", description: "[0-9]" },
-        peg$c115 = /^[0-9a-fA-F]/,
-        peg$c116 = { type: "class", value: "[0-9a-fA-F]", description: "[0-9a-fA-F]" },
-        peg$c117 = /^[a-z]/,
-        peg$c118 = { type: "class", value: "[a-z]", description: "[a-z]" },
-        peg$c119 = /^[A-Z]/,
-        peg$c120 = { type: "class", value: "[A-Z]", description: "[A-Z]" },
-        peg$c121 = { type: "other", description: "comment" },
-        peg$c122 = "//",
-        peg$c123 = { type: "literal", value: "//", description: "\"//\"" },
-        peg$c124 = "/*",
-        peg$c125 = { type: "literal", value: "/*", description: "\"/*\"" },
-        peg$c126 = "*/",
-        peg$c127 = { type: "literal", value: "*/", description: "\"*/\"" },
-        peg$c128 = { type: "other", description: "end of line" },
-        peg$c129 = "\n",
-        peg$c130 = { type: "literal", value: "\n", description: "\"\\n\"" },
-        peg$c131 = "\r\n",
-        peg$c132 = { type: "literal", value: "\r\n", description: "\"\\r\\n\"" },
-        peg$c133 = "\r",
-        peg$c134 = { type: "literal", value: "\r", description: "\"\\r\"" },
-        peg$c135 = "\u2028",
-        peg$c136 = { type: "literal", value: "\u2028", description: "\"\\u2028\"" },
-        peg$c137 = "\u2029",
-        peg$c138 = { type: "literal", value: "\u2029", description: "\"\\u2029\"" },
-        peg$c139 = /^[\n\r\u2028\u2029]/,
-        peg$c140 = { type: "class", value: "[\\n\\r\\u2028\\u2029]", description: "[\\n\\r\\u2028\\u2029]" },
-        peg$c141 = { type: "other", description: "whitespace" },
-        peg$c142 = /^[ \t\x0B\f\xA0\uFEFF\u1680\u180E\u2000-\u200A\u202F\u205F\u3000]/,
-        peg$c143 = { type: "class", value: "[ \\t\\x0B\\f\\xA0\\uFEFF\\u1680\\u180E\\u2000-\\u200A\\u202F\\u205F\\u3000]", description: "[ \\t\\x0B\\f\\xA0\\uFEFF\\u1680\\u180E\\u2000-\\u200A\\u202F\\u205F\\u3000]" },
+        peg$c111 = "\\u",
+        peg$c112 = { type: "literal", value: "\\u", description: "\"\\\\u\"" },
+        peg$c113 = function(eol) { return eol; },
+        peg$c114 = /^[0-9]/,
+        peg$c115 = { type: "class", value: "[0-9]", description: "[0-9]" },
+        peg$c116 = /^[0-9a-fA-F]/,
+        peg$c117 = { type: "class", value: "[0-9a-fA-F]", description: "[0-9a-fA-F]" },
+        peg$c118 = /^[a-z]/,
+        peg$c119 = { type: "class", value: "[a-z]", description: "[a-z]" },
+        peg$c120 = /^[A-Z]/,
+        peg$c121 = { type: "class", value: "[A-Z]", description: "[A-Z]" },
+        peg$c122 = { type: "other", description: "comment" },
+        peg$c123 = "//",
+        peg$c124 = { type: "literal", value: "//", description: "\"//\"" },
+        peg$c125 = "/*",
+        peg$c126 = { type: "literal", value: "/*", description: "\"/*\"" },
+        peg$c127 = "*/",
+        peg$c128 = { type: "literal", value: "*/", description: "\"*/\"" },
+        peg$c129 = { type: "other", description: "end of line" },
+        peg$c130 = "\n",
+        peg$c131 = { type: "literal", value: "\n", description: "\"\\n\"" },
+        peg$c132 = "\r\n",
+        peg$c133 = { type: "literal", value: "\r\n", description: "\"\\r\\n\"" },
+        peg$c134 = "\r",
+        peg$c135 = { type: "literal", value: "\r", description: "\"\\r\"" },
+        peg$c136 = "\u2028",
+        peg$c137 = { type: "literal", value: "\u2028", description: "\"\\u2028\"" },
+        peg$c138 = "\u2029",
+        peg$c139 = { type: "literal", value: "\u2029", description: "\"\\u2029\"" },
+        peg$c140 = /^[\n\r\u2028\u2029]/,
+        peg$c141 = { type: "class", value: "[\\n\\r\\u2028\\u2029]", description: "[\\n\\r\\u2028\\u2029]" },
+        peg$c142 = { type: "other", description: "whitespace" },
+        peg$c143 = /^[ \t\x0B\f\xA0\uFEFF\u1680\u180E\u2000-\u200A\u202F\u205F\u3000]/,
+        peg$c144 = { type: "class", value: "[ \\t\\x0B\\f\\xA0\\uFEFF\\u1680\\u180E\\u2000-\\u200A\\u202F\\u205F\\u3000]", description: "[ \\t\\x0B\\f\\xA0\\uFEFF\\u1680\\u180E\\u2000-\\u200A\\u202F\\u205F\\u3000]" },
 
         peg$currPos          = 0,
         peg$reportedPos      = 0,
@@ -986,14 +987,14 @@ module.exports = (function() {
         }
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c1;
+          s2 = peg$c18;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
         }
         if (s2 !== peg$FAILED) {
           peg$reportedPos = s0;
-          s1 = peg$c18(s1);
+          s1 = peg$c19(s1);
           if (s1 === peg$FAILED) {
             peg$currPos = s0;
             s0 = s1;
@@ -1017,7 +1018,7 @@ module.exports = (function() {
             s1 = peg$parsedot();
             if (s1 !== peg$FAILED) {
               peg$reportedPos = s0;
-              s1 = peg$c19();
+              s1 = peg$c20();
             }
             if (s1 === peg$FAILED) {
               peg$currPos = s0;
@@ -1034,7 +1035,7 @@ module.exports = (function() {
                   s3 = peg$parserparen();
                   if (s3 !== peg$FAILED) {
                     peg$reportedPos = s0;
-                    s1 = peg$c20(s2);
+                    s1 = peg$c21(s2);
                     if (s1 === peg$FAILED) {
                       peg$currPos = s0;
                       s0 = s1;
@@ -1071,7 +1072,7 @@ module.exports = (function() {
         s2 = peg$parse__();
         if (s2 !== peg$FAILED) {
           peg$reportedPos = s0;
-          s1 = peg$c22(s1);
+          s1 = peg$c23(s1);
           if (s1 === peg$FAILED) {
             peg$currPos = s0;
             s0 = s1;
@@ -1089,7 +1090,7 @@ module.exports = (function() {
       peg$silentFails--;
       if (s0 === peg$FAILED) {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c21); }
+        if (peg$silentFails === 0) { peg$fail(peg$c22); }
       }
 
       return s0;
@@ -1101,11 +1102,11 @@ module.exports = (function() {
       s0 = peg$currPos;
       s1 = peg$currPos;
       if (input.charCodeAt(peg$currPos) === 123) {
-        s2 = peg$c23;
+        s2 = peg$c24;
         peg$currPos++;
       } else {
         s2 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c24); }
+        if (peg$silentFails === 0) { peg$fail(peg$c25); }
       }
       if (s2 !== peg$FAILED) {
         s3 = [];
@@ -1122,11 +1123,11 @@ module.exports = (function() {
         }
         if (s3 !== peg$FAILED) {
           if (input.charCodeAt(peg$currPos) === 125) {
-            s4 = peg$c25;
+            s4 = peg$c26;
             peg$currPos++;
           } else {
             s4 = peg$FAILED;
-            if (peg$silentFails === 0) { peg$fail(peg$c26); }
+            if (peg$silentFails === 0) { peg$fail(peg$c27); }
           }
           if (s4 !== peg$FAILED) {
             s2 = [s2, s3, s4];
@@ -1171,12 +1172,12 @@ module.exports = (function() {
     function peg$parsenonBraceCharacter() {
       var s0;
 
-      if (peg$c27.test(input.charAt(peg$currPos))) {
+      if (peg$c28.test(input.charAt(peg$currPos))) {
         s0 = input.charAt(peg$currPos);
         peg$currPos++;
       } else {
         s0 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c28); }
+        if (peg$silentFails === 0) { peg$fail(peg$c29); }
       }
 
       return s0;
@@ -1187,17 +1188,17 @@ module.exports = (function() {
 
       s0 = peg$currPos;
       if (input.charCodeAt(peg$currPos) === 61) {
-        s1 = peg$c29;
+        s1 = peg$c30;
         peg$currPos++;
       } else {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c30); }
+        if (peg$silentFails === 0) { peg$fail(peg$c31); }
       }
       if (s1 !== peg$FAILED) {
         s2 = peg$parse__();
         if (s2 !== peg$FAILED) {
           peg$reportedPos = s0;
-          s1 = peg$c31();
+          s1 = peg$c32();
           if (s1 === peg$FAILED) {
             peg$currPos = s0;
             s0 = s1;
@@ -1221,17 +1222,17 @@ module.exports = (function() {
 
       s0 = peg$currPos;
       if (input.charCodeAt(peg$currPos) === 58) {
-        s1 = peg$c32;
+        s1 = peg$c33;
         peg$currPos++;
       } else {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c33); }
+        if (peg$silentFails === 0) { peg$fail(peg$c34); }
       }
       if (s1 !== peg$FAILED) {
         s2 = peg$parse__();
         if (s2 !== peg$FAILED) {
           peg$reportedPos = s0;
-          s1 = peg$c34();
+          s1 = peg$c35();
           if (s1 === peg$FAILED) {
             peg$currPos = s0;
             s0 = s1;
@@ -1255,17 +1256,17 @@ module.exports = (function() {
 
       s0 = peg$currPos;
       if (input.charCodeAt(peg$currPos) === 59) {
-        s1 = peg$c35;
+        s1 = peg$c36;
         peg$currPos++;
       } else {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c36); }
+        if (peg$silentFails === 0) { peg$fail(peg$c37); }
       }
       if (s1 !== peg$FAILED) {
         s2 = peg$parse__();
         if (s2 !== peg$FAILED) {
           peg$reportedPos = s0;
-          s1 = peg$c37();
+          s1 = peg$c38();
           if (s1 === peg$FAILED) {
             peg$currPos = s0;
             s0 = s1;
@@ -1289,17 +1290,17 @@ module.exports = (function() {
 
       s0 = peg$currPos;
       if (input.charCodeAt(peg$currPos) === 47) {
-        s1 = peg$c38;
+        s1 = peg$c39;
         peg$currPos++;
       } else {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c39); }
+        if (peg$silentFails === 0) { peg$fail(peg$c40); }
       }
       if (s1 !== peg$FAILED) {
         s2 = peg$parse__();
         if (s2 !== peg$FAILED) {
           peg$reportedPos = s0;
-          s1 = peg$c40();
+          s1 = peg$c41();
           if (s1 === peg$FAILED) {
             peg$currPos = s0;
             s0 = s1;
@@ -1323,17 +1324,17 @@ module.exports = (function() {
 
       s0 = peg$currPos;
       if (input.charCodeAt(peg$currPos) === 38) {
-        s1 = peg$c41;
+        s1 = peg$c42;
         peg$currPos++;
       } else {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c42); }
+        if (peg$silentFails === 0) { peg$fail(peg$c43); }
       }
       if (s1 !== peg$FAILED) {
         s2 = peg$parse__();
         if (s2 !== peg$FAILED) {
           peg$reportedPos = s0;
-          s1 = peg$c43();
+          s1 = peg$c44();
           if (s1 === peg$FAILED) {
             peg$currPos = s0;
             s0 = s1;
@@ -1357,17 +1358,17 @@ module.exports = (function() {
 
       s0 = peg$currPos;
       if (input.charCodeAt(peg$currPos) === 33) {
-        s1 = peg$c44;
+        s1 = peg$c45;
         peg$currPos++;
       } else {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c45); }
+        if (peg$silentFails === 0) { peg$fail(peg$c46); }
       }
       if (s1 !== peg$FAILED) {
         s2 = peg$parse__();
         if (s2 !== peg$FAILED) {
           peg$reportedPos = s0;
-          s1 = peg$c46();
+          s1 = peg$c47();
           if (s1 === peg$FAILED) {
             peg$currPos = s0;
             s0 = s1;
@@ -1391,17 +1392,17 @@ module.exports = (function() {
 
       s0 = peg$currPos;
       if (input.charCodeAt(peg$currPos) === 36) {
-        s1 = peg$c47;
+        s1 = peg$c48;
         peg$currPos++;
       } else {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c48); }
+        if (peg$silentFails === 0) { peg$fail(peg$c49); }
       }
       if (s1 !== peg$FAILED) {
         s2 = peg$parse__();
         if (s2 !== peg$FAILED) {
           peg$reportedPos = s0;
-          s1 = peg$c49();
+          s1 = peg$c50();
           if (s1 === peg$FAILED) {
             peg$currPos = s0;
             s0 = s1;
@@ -1425,17 +1426,17 @@ module.exports = (function() {
 
       s0 = peg$currPos;
       if (input.charCodeAt(peg$currPos) === 63) {
-        s1 = peg$c50;
+        s1 = peg$c51;
         peg$currPos++;
       } else {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c51); }
+        if (peg$silentFails === 0) { peg$fail(peg$c52); }
       }
       if (s1 !== peg$FAILED) {
         s2 = peg$parse__();
         if (s2 !== peg$FAILED) {
           peg$reportedPos = s0;
-          s1 = peg$c52();
+          s1 = peg$c53();
           if (s1 === peg$FAILED) {
             peg$currPos = s0;
             s0 = s1;
@@ -1459,17 +1460,17 @@ module.exports = (function() {
 
       s0 = peg$currPos;
       if (input.charCodeAt(peg$currPos) === 42) {
-        s1 = peg$c53;
+        s1 = peg$c54;
         peg$currPos++;
       } else {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c54); }
+        if (peg$silentFails === 0) { peg$fail(peg$c55); }
       }
       if (s1 !== peg$FAILED) {
         s2 = peg$parse__();
         if (s2 !== peg$FAILED) {
           peg$reportedPos = s0;
-          s1 = peg$c55();
+          s1 = peg$c56();
           if (s1 === peg$FAILED) {
             peg$currPos = s0;
             s0 = s1;
@@ -1493,17 +1494,17 @@ module.exports = (function() {
 
       s0 = peg$currPos;
       if (input.charCodeAt(peg$currPos) === 43) {
-        s1 = peg$c56;
+        s1 = peg$c57;
         peg$currPos++;
       } else {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c57); }
+        if (peg$silentFails === 0) { peg$fail(peg$c58); }
       }
       if (s1 !== peg$FAILED) {
         s2 = peg$parse__();
         if (s2 !== peg$FAILED) {
           peg$reportedPos = s0;
-          s1 = peg$c58();
+          s1 = peg$c59();
           if (s1 === peg$FAILED) {
             peg$currPos = s0;
             s0 = s1;
@@ -1527,17 +1528,17 @@ module.exports = (function() {
 
       s0 = peg$currPos;
       if (input.charCodeAt(peg$currPos) === 40) {
-        s1 = peg$c59;
+        s1 = peg$c60;
         peg$currPos++;
       } else {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c60); }
+        if (peg$silentFails === 0) { peg$fail(peg$c61); }
       }
       if (s1 !== peg$FAILED) {
         s2 = peg$parse__();
         if (s2 !== peg$FAILED) {
           peg$reportedPos = s0;
-          s1 = peg$c61();
+          s1 = peg$c62();
           if (s1 === peg$FAILED) {
             peg$currPos = s0;
             s0 = s1;
@@ -1561,17 +1562,17 @@ module.exports = (function() {
 
       s0 = peg$currPos;
       if (input.charCodeAt(peg$currPos) === 41) {
-        s1 = peg$c62;
+        s1 = peg$c63;
         peg$currPos++;
       } else {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c63); }
+        if (peg$silentFails === 0) { peg$fail(peg$c64); }
       }
       if (s1 !== peg$FAILED) {
         s2 = peg$parse__();
         if (s2 !== peg$FAILED) {
           peg$reportedPos = s0;
-          s1 = peg$c64();
+          s1 = peg$c65();
           if (s1 === peg$FAILED) {
             peg$currPos = s0;
             s0 = s1;
@@ -1595,17 +1596,17 @@ module.exports = (function() {
 
       s0 = peg$currPos;
       if (input.charCodeAt(peg$currPos) === 46) {
-        s1 = peg$c65;
+        s1 = peg$c66;
         peg$currPos++;
       } else {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c66); }
+        if (peg$silentFails === 0) { peg$fail(peg$c67); }
       }
       if (s1 !== peg$FAILED) {
         s2 = peg$parse__();
         if (s2 !== peg$FAILED) {
           peg$reportedPos = s0;
-          s1 = peg$c67();
+          s1 = peg$c68();
           if (s1 === peg$FAILED) {
             peg$currPos = s0;
             s0 = s1;
@@ -1634,11 +1635,11 @@ module.exports = (function() {
       s3 = peg$parseletter();
       if (s3 === peg$FAILED) {
         if (input.charCodeAt(peg$currPos) === 95) {
-          s3 = peg$c69;
+          s3 = peg$c70;
           peg$currPos++;
         } else {
           s3 = peg$FAILED;
-          if (peg$silentFails === 0) { peg$fail(peg$c70); }
+          if (peg$silentFails === 0) { peg$fail(peg$c71); }
         }
       }
       if (s3 !== peg$FAILED) {
@@ -1648,11 +1649,11 @@ module.exports = (function() {
           s5 = peg$parsedigit();
           if (s5 === peg$FAILED) {
             if (input.charCodeAt(peg$currPos) === 95) {
-              s5 = peg$c69;
+              s5 = peg$c70;
               peg$currPos++;
             } else {
               s5 = peg$FAILED;
-              if (peg$silentFails === 0) { peg$fail(peg$c70); }
+              if (peg$silentFails === 0) { peg$fail(peg$c71); }
             }
           }
         }
@@ -1663,11 +1664,11 @@ module.exports = (function() {
             s5 = peg$parsedigit();
             if (s5 === peg$FAILED) {
               if (input.charCodeAt(peg$currPos) === 95) {
-                s5 = peg$c69;
+                s5 = peg$c70;
                 peg$currPos++;
               } else {
                 s5 = peg$FAILED;
-                if (peg$silentFails === 0) { peg$fail(peg$c70); }
+                if (peg$silentFails === 0) { peg$fail(peg$c71); }
               }
             }
           }
@@ -1691,7 +1692,7 @@ module.exports = (function() {
         s2 = peg$parse__();
         if (s2 !== peg$FAILED) {
           peg$reportedPos = s0;
-          s1 = peg$c71(s1);
+          s1 = peg$c72(s1);
           if (s1 === peg$FAILED) {
             peg$currPos = s0;
             s0 = s1;
@@ -1709,7 +1710,7 @@ module.exports = (function() {
       peg$silentFails--;
       if (s0 === peg$FAILED) {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c68); }
+        if (peg$silentFails === 0) { peg$fail(peg$c69); }
       }
 
       return s0;
@@ -1726,11 +1727,11 @@ module.exports = (function() {
       }
       if (s1 !== peg$FAILED) {
         if (input.charCodeAt(peg$currPos) === 105) {
-          s2 = peg$c73;
+          s2 = peg$c74;
           peg$currPos++;
         } else {
           s2 = peg$FAILED;
-          if (peg$silentFails === 0) { peg$fail(peg$c74); }
+          if (peg$silentFails === 0) { peg$fail(peg$c75); }
         }
         if (s2 === peg$FAILED) {
           s2 = peg$c1;
@@ -1739,7 +1740,7 @@ module.exports = (function() {
           s3 = peg$parse__();
           if (s3 !== peg$FAILED) {
             peg$reportedPos = s0;
-            s1 = peg$c75(s1, s2);
+            s1 = peg$c76(s1, s2);
             if (s1 === peg$FAILED) {
               peg$currPos = s0;
               s0 = s1;
@@ -1761,7 +1762,7 @@ module.exports = (function() {
       peg$silentFails--;
       if (s0 === peg$FAILED) {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c72); }
+        if (peg$silentFails === 0) { peg$fail(peg$c73); }
       }
 
       return s0;
@@ -1780,7 +1781,7 @@ module.exports = (function() {
         s2 = peg$parse__();
         if (s2 !== peg$FAILED) {
           peg$reportedPos = s0;
-          s1 = peg$c77(s1);
+          s1 = peg$c78(s1);
           if (s1 === peg$FAILED) {
             peg$currPos = s0;
             s0 = s1;
@@ -1798,7 +1799,7 @@ module.exports = (function() {
       peg$silentFails--;
       if (s0 === peg$FAILED) {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c76); }
+        if (peg$silentFails === 0) { peg$fail(peg$c77); }
       }
 
       return s0;
@@ -1809,11 +1810,11 @@ module.exports = (function() {
 
       s0 = peg$currPos;
       if (input.charCodeAt(peg$currPos) === 34) {
-        s1 = peg$c78;
+        s1 = peg$c79;
         peg$currPos++;
       } else {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c79); }
+        if (peg$silentFails === 0) { peg$fail(peg$c80); }
       }
       if (s1 !== peg$FAILED) {
         s2 = [];
@@ -1824,15 +1825,15 @@ module.exports = (function() {
         }
         if (s2 !== peg$FAILED) {
           if (input.charCodeAt(peg$currPos) === 34) {
-            s3 = peg$c78;
+            s3 = peg$c79;
             peg$currPos++;
           } else {
             s3 = peg$FAILED;
-            if (peg$silentFails === 0) { peg$fail(peg$c79); }
+            if (peg$silentFails === 0) { peg$fail(peg$c80); }
           }
           if (s3 !== peg$FAILED) {
             peg$reportedPos = s0;
-            s1 = peg$c80(s2);
+            s1 = peg$c81(s2);
             if (s1 === peg$FAILED) {
               peg$currPos = s0;
               s0 = s1;
@@ -1885,19 +1886,19 @@ module.exports = (function() {
       s1 = peg$currPos;
       peg$silentFails++;
       if (input.charCodeAt(peg$currPos) === 34) {
-        s2 = peg$c78;
+        s2 = peg$c79;
         peg$currPos++;
       } else {
         s2 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c79); }
+        if (peg$silentFails === 0) { peg$fail(peg$c80); }
       }
       if (s2 === peg$FAILED) {
         if (input.charCodeAt(peg$currPos) === 92) {
-          s2 = peg$c81;
+          s2 = peg$c82;
           peg$currPos++;
         } else {
           s2 = peg$FAILED;
-          if (peg$silentFails === 0) { peg$fail(peg$c82); }
+          if (peg$silentFails === 0) { peg$fail(peg$c83); }
         }
         if (s2 === peg$FAILED) {
           s2 = peg$parseeolChar();
@@ -1905,7 +1906,7 @@ module.exports = (function() {
       }
       peg$silentFails--;
       if (s2 === peg$FAILED) {
-        s1 = peg$c1;
+        s1 = peg$c18;
       } else {
         peg$currPos = s1;
         s1 = peg$c0;
@@ -1916,11 +1917,11 @@ module.exports = (function() {
           peg$currPos++;
         } else {
           s2 = peg$FAILED;
-          if (peg$silentFails === 0) { peg$fail(peg$c83); }
+          if (peg$silentFails === 0) { peg$fail(peg$c84); }
         }
         if (s2 !== peg$FAILED) {
           peg$reportedPos = s0;
-          s1 = peg$c84(s2);
+          s1 = peg$c85(s2);
           if (s1 === peg$FAILED) {
             peg$currPos = s0;
             s0 = s1;
@@ -1944,11 +1945,11 @@ module.exports = (function() {
 
       s0 = peg$currPos;
       if (input.charCodeAt(peg$currPos) === 39) {
-        s1 = peg$c85;
+        s1 = peg$c86;
         peg$currPos++;
       } else {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c86); }
+        if (peg$silentFails === 0) { peg$fail(peg$c87); }
       }
       if (s1 !== peg$FAILED) {
         s2 = [];
@@ -1959,15 +1960,15 @@ module.exports = (function() {
         }
         if (s2 !== peg$FAILED) {
           if (input.charCodeAt(peg$currPos) === 39) {
-            s3 = peg$c85;
+            s3 = peg$c86;
             peg$currPos++;
           } else {
             s3 = peg$FAILED;
-            if (peg$silentFails === 0) { peg$fail(peg$c86); }
+            if (peg$silentFails === 0) { peg$fail(peg$c87); }
           }
           if (s3 !== peg$FAILED) {
             peg$reportedPos = s0;
-            s1 = peg$c80(s2);
+            s1 = peg$c81(s2);
             if (s1 === peg$FAILED) {
               peg$currPos = s0;
               s0 = s1;
@@ -2020,19 +2021,19 @@ module.exports = (function() {
       s1 = peg$currPos;
       peg$silentFails++;
       if (input.charCodeAt(peg$currPos) === 39) {
-        s2 = peg$c85;
+        s2 = peg$c86;
         peg$currPos++;
       } else {
         s2 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c86); }
+        if (peg$silentFails === 0) { peg$fail(peg$c87); }
       }
       if (s2 === peg$FAILED) {
         if (input.charCodeAt(peg$currPos) === 92) {
-          s2 = peg$c81;
+          s2 = peg$c82;
           peg$currPos++;
         } else {
           s2 = peg$FAILED;
-          if (peg$silentFails === 0) { peg$fail(peg$c82); }
+          if (peg$silentFails === 0) { peg$fail(peg$c83); }
         }
         if (s2 === peg$FAILED) {
           s2 = peg$parseeolChar();
@@ -2040,7 +2041,7 @@ module.exports = (function() {
       }
       peg$silentFails--;
       if (s2 === peg$FAILED) {
-        s1 = peg$c1;
+        s1 = peg$c18;
       } else {
         peg$currPos = s1;
         s1 = peg$c0;
@@ -2051,11 +2052,11 @@ module.exports = (function() {
           peg$currPos++;
         } else {
           s2 = peg$FAILED;
-          if (peg$silentFails === 0) { peg$fail(peg$c83); }
+          if (peg$silentFails === 0) { peg$fail(peg$c84); }
         }
         if (s2 !== peg$FAILED) {
           peg$reportedPos = s0;
-          s1 = peg$c84(s2);
+          s1 = peg$c85(s2);
           if (s1 === peg$FAILED) {
             peg$currPos = s0;
             s0 = s1;
@@ -2080,19 +2081,19 @@ module.exports = (function() {
       peg$silentFails++;
       s0 = peg$currPos;
       if (input.charCodeAt(peg$currPos) === 91) {
-        s1 = peg$c88;
+        s1 = peg$c89;
         peg$currPos++;
       } else {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c89); }
+        if (peg$silentFails === 0) { peg$fail(peg$c90); }
       }
       if (s1 !== peg$FAILED) {
         if (input.charCodeAt(peg$currPos) === 94) {
-          s2 = peg$c90;
+          s2 = peg$c91;
           peg$currPos++;
         } else {
           s2 = peg$FAILED;
-          if (peg$silentFails === 0) { peg$fail(peg$c91); }
+          if (peg$silentFails === 0) { peg$fail(peg$c92); }
         }
         if (s2 === peg$FAILED) {
           s2 = peg$c1;
@@ -2112,19 +2113,19 @@ module.exports = (function() {
           }
           if (s3 !== peg$FAILED) {
             if (input.charCodeAt(peg$currPos) === 93) {
-              s4 = peg$c92;
+              s4 = peg$c93;
               peg$currPos++;
             } else {
               s4 = peg$FAILED;
-              if (peg$silentFails === 0) { peg$fail(peg$c93); }
+              if (peg$silentFails === 0) { peg$fail(peg$c94); }
             }
             if (s4 !== peg$FAILED) {
               if (input.charCodeAt(peg$currPos) === 105) {
-                s5 = peg$c73;
+                s5 = peg$c74;
                 peg$currPos++;
               } else {
                 s5 = peg$FAILED;
-                if (peg$silentFails === 0) { peg$fail(peg$c74); }
+                if (peg$silentFails === 0) { peg$fail(peg$c75); }
               }
               if (s5 === peg$FAILED) {
                 s5 = peg$c1;
@@ -2133,7 +2134,7 @@ module.exports = (function() {
                 s6 = peg$parse__();
                 if (s6 !== peg$FAILED) {
                   peg$reportedPos = s0;
-                  s1 = peg$c94(s2, s3, s5);
+                  s1 = peg$c95(s2, s3, s5);
                   if (s1 === peg$FAILED) {
                     peg$currPos = s0;
                     s0 = s1;
@@ -2167,7 +2168,7 @@ module.exports = (function() {
       peg$silentFails--;
       if (s0 === peg$FAILED) {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c87); }
+        if (peg$silentFails === 0) { peg$fail(peg$c88); }
       }
 
       return s0;
@@ -2180,17 +2181,17 @@ module.exports = (function() {
       s1 = peg$parseclassCharacter();
       if (s1 !== peg$FAILED) {
         if (input.charCodeAt(peg$currPos) === 45) {
-          s2 = peg$c95;
+          s2 = peg$c96;
           peg$currPos++;
         } else {
           s2 = peg$FAILED;
-          if (peg$silentFails === 0) { peg$fail(peg$c96); }
+          if (peg$silentFails === 0) { peg$fail(peg$c97); }
         }
         if (s2 !== peg$FAILED) {
           s3 = peg$parseclassCharacter();
           if (s3 !== peg$FAILED) {
             peg$reportedPos = s0;
-            s1 = peg$c97(s1, s3);
+            s1 = peg$c98(s1, s3);
             if (s1 === peg$FAILED) {
               peg$currPos = s0;
               s0 = s1;
@@ -2220,7 +2221,7 @@ module.exports = (function() {
       s1 = peg$parsebracketDelimitedCharacter();
       if (s1 !== peg$FAILED) {
         peg$reportedPos = s0;
-        s1 = peg$c98(s1);
+        s1 = peg$c99(s1);
       }
       if (s1 === peg$FAILED) {
         peg$currPos = s0;
@@ -2262,19 +2263,19 @@ module.exports = (function() {
       s1 = peg$currPos;
       peg$silentFails++;
       if (input.charCodeAt(peg$currPos) === 93) {
-        s2 = peg$c92;
+        s2 = peg$c93;
         peg$currPos++;
       } else {
         s2 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c93); }
+        if (peg$silentFails === 0) { peg$fail(peg$c94); }
       }
       if (s2 === peg$FAILED) {
         if (input.charCodeAt(peg$currPos) === 92) {
-          s2 = peg$c81;
+          s2 = peg$c82;
           peg$currPos++;
         } else {
           s2 = peg$FAILED;
-          if (peg$silentFails === 0) { peg$fail(peg$c82); }
+          if (peg$silentFails === 0) { peg$fail(peg$c83); }
         }
         if (s2 === peg$FAILED) {
           s2 = peg$parseeolChar();
@@ -2282,7 +2283,7 @@ module.exports = (function() {
       }
       peg$silentFails--;
       if (s2 === peg$FAILED) {
-        s1 = peg$c1;
+        s1 = peg$c18;
       } else {
         peg$currPos = s1;
         s1 = peg$c0;
@@ -2293,11 +2294,11 @@ module.exports = (function() {
           peg$currPos++;
         } else {
           s2 = peg$FAILED;
-          if (peg$silentFails === 0) { peg$fail(peg$c83); }
+          if (peg$silentFails === 0) { peg$fail(peg$c84); }
         }
         if (s2 !== peg$FAILED) {
           peg$reportedPos = s0;
-          s1 = peg$c84(s2);
+          s1 = peg$c85(s2);
           if (s1 === peg$FAILED) {
             peg$currPos = s0;
             s0 = s1;
@@ -2321,11 +2322,11 @@ module.exports = (function() {
 
       s0 = peg$currPos;
       if (input.charCodeAt(peg$currPos) === 92) {
-        s1 = peg$c81;
+        s1 = peg$c82;
         peg$currPos++;
       } else {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c82); }
+        if (peg$silentFails === 0) { peg$fail(peg$c83); }
       }
       if (s1 !== peg$FAILED) {
         s2 = peg$currPos;
@@ -2333,19 +2334,19 @@ module.exports = (function() {
         s3 = peg$parsedigit();
         if (s3 === peg$FAILED) {
           if (input.charCodeAt(peg$currPos) === 120) {
-            s3 = peg$c99;
+            s3 = peg$c100;
             peg$currPos++;
           } else {
             s3 = peg$FAILED;
-            if (peg$silentFails === 0) { peg$fail(peg$c100); }
+            if (peg$silentFails === 0) { peg$fail(peg$c101); }
           }
           if (s3 === peg$FAILED) {
             if (input.charCodeAt(peg$currPos) === 117) {
-              s3 = peg$c101;
+              s3 = peg$c102;
               peg$currPos++;
             } else {
               s3 = peg$FAILED;
-              if (peg$silentFails === 0) { peg$fail(peg$c102); }
+              if (peg$silentFails === 0) { peg$fail(peg$c103); }
             }
             if (s3 === peg$FAILED) {
               s3 = peg$parseeolChar();
@@ -2354,7 +2355,7 @@ module.exports = (function() {
         }
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c1;
+          s2 = peg$c18;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -2365,11 +2366,11 @@ module.exports = (function() {
             peg$currPos++;
           } else {
             s3 = peg$FAILED;
-            if (peg$silentFails === 0) { peg$fail(peg$c83); }
+            if (peg$silentFails === 0) { peg$fail(peg$c84); }
           }
           if (s3 !== peg$FAILED) {
             peg$reportedPos = s0;
-            s1 = peg$c103(s3);
+            s1 = peg$c104(s3);
             if (s1 === peg$FAILED) {
               peg$currPos = s0;
               s0 = s1;
@@ -2396,12 +2397,12 @@ module.exports = (function() {
       var s0, s1, s2, s3;
 
       s0 = peg$currPos;
-      if (input.substr(peg$currPos, 2) === peg$c104) {
-        s1 = peg$c104;
+      if (input.substr(peg$currPos, 2) === peg$c105) {
+        s1 = peg$c105;
         peg$currPos += 2;
       } else {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c105); }
+        if (peg$silentFails === 0) { peg$fail(peg$c106); }
       }
       if (s1 !== peg$FAILED) {
         s2 = peg$currPos;
@@ -2409,14 +2410,14 @@ module.exports = (function() {
         s3 = peg$parsedigit();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c1;
+          s2 = peg$c18;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
         }
         if (s2 !== peg$FAILED) {
           peg$reportedPos = s0;
-          s1 = peg$c106();
+          s1 = peg$c107();
           if (s1 === peg$FAILED) {
             peg$currPos = s0;
             s0 = s1;
@@ -2439,12 +2440,12 @@ module.exports = (function() {
       var s0, s1, s2, s3, s4, s5;
 
       s0 = peg$currPos;
-      if (input.substr(peg$currPos, 2) === peg$c107) {
-        s1 = peg$c107;
+      if (input.substr(peg$currPos, 2) === peg$c108) {
+        s1 = peg$c108;
         peg$currPos += 2;
       } else {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c108); }
+        if (peg$silentFails === 0) { peg$fail(peg$c109); }
       }
       if (s1 !== peg$FAILED) {
         s2 = peg$currPos;
@@ -2469,7 +2470,7 @@ module.exports = (function() {
         s2 = s3;
         if (s2 !== peg$FAILED) {
           peg$reportedPos = s0;
-          s1 = peg$c109(s2);
+          s1 = peg$c110(s2);
           if (s1 === peg$FAILED) {
             peg$currPos = s0;
             s0 = s1;
@@ -2492,12 +2493,12 @@ module.exports = (function() {
       var s0, s1, s2, s3, s4, s5, s6, s7;
 
       s0 = peg$currPos;
-      if (input.substr(peg$currPos, 2) === peg$c110) {
-        s1 = peg$c110;
+      if (input.substr(peg$currPos, 2) === peg$c111) {
+        s1 = peg$c111;
         peg$currPos += 2;
       } else {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c111); }
+        if (peg$silentFails === 0) { peg$fail(peg$c112); }
       }
       if (s1 !== peg$FAILED) {
         s2 = peg$currPos;
@@ -2534,7 +2535,7 @@ module.exports = (function() {
         s2 = s3;
         if (s2 !== peg$FAILED) {
           peg$reportedPos = s0;
-          s1 = peg$c109(s2);
+          s1 = peg$c110(s2);
           if (s1 === peg$FAILED) {
             peg$currPos = s0;
             s0 = s1;
@@ -2558,17 +2559,17 @@ module.exports = (function() {
 
       s0 = peg$currPos;
       if (input.charCodeAt(peg$currPos) === 92) {
-        s1 = peg$c81;
+        s1 = peg$c82;
         peg$currPos++;
       } else {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c82); }
+        if (peg$silentFails === 0) { peg$fail(peg$c83); }
       }
       if (s1 !== peg$FAILED) {
         s2 = peg$parseeol();
         if (s2 !== peg$FAILED) {
           peg$reportedPos = s0;
-          s1 = peg$c112(s2);
+          s1 = peg$c113(s2);
           if (s1 === peg$FAILED) {
             peg$currPos = s0;
             s0 = s1;
@@ -2590,12 +2591,12 @@ module.exports = (function() {
     function peg$parsedigit() {
       var s0;
 
-      if (peg$c113.test(input.charAt(peg$currPos))) {
+      if (peg$c114.test(input.charAt(peg$currPos))) {
         s0 = input.charAt(peg$currPos);
         peg$currPos++;
       } else {
         s0 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c114); }
+        if (peg$silentFails === 0) { peg$fail(peg$c115); }
       }
 
       return s0;
@@ -2604,12 +2605,12 @@ module.exports = (function() {
     function peg$parsehexDigit() {
       var s0;
 
-      if (peg$c115.test(input.charAt(peg$currPos))) {
+      if (peg$c116.test(input.charAt(peg$currPos))) {
         s0 = input.charAt(peg$currPos);
         peg$currPos++;
       } else {
         s0 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c116); }
+        if (peg$silentFails === 0) { peg$fail(peg$c117); }
       }
 
       return s0;
@@ -2629,12 +2630,12 @@ module.exports = (function() {
     function peg$parselowerCaseLetter() {
       var s0;
 
-      if (peg$c117.test(input.charAt(peg$currPos))) {
+      if (peg$c118.test(input.charAt(peg$currPos))) {
         s0 = input.charAt(peg$currPos);
         peg$currPos++;
       } else {
         s0 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c118); }
+        if (peg$silentFails === 0) { peg$fail(peg$c119); }
       }
 
       return s0;
@@ -2643,12 +2644,12 @@ module.exports = (function() {
     function peg$parseupperCaseLetter() {
       var s0;
 
-      if (peg$c119.test(input.charAt(peg$currPos))) {
+      if (peg$c120.test(input.charAt(peg$currPos))) {
         s0 = input.charAt(peg$currPos);
         peg$currPos++;
       } else {
         s0 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c120); }
+        if (peg$silentFails === 0) { peg$fail(peg$c121); }
       }
 
       return s0;
@@ -2690,7 +2691,7 @@ module.exports = (function() {
       peg$silentFails--;
       if (s0 === peg$FAILED) {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c121); }
+        if (peg$silentFails === 0) { peg$fail(peg$c122); }
       }
 
       return s0;
@@ -2700,12 +2701,12 @@ module.exports = (function() {
       var s0, s1, s2, s3, s4, s5;
 
       s0 = peg$currPos;
-      if (input.substr(peg$currPos, 2) === peg$c122) {
-        s1 = peg$c122;
+      if (input.substr(peg$currPos, 2) === peg$c123) {
+        s1 = peg$c123;
         peg$currPos += 2;
       } else {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c123); }
+        if (peg$silentFails === 0) { peg$fail(peg$c124); }
       }
       if (s1 !== peg$FAILED) {
         s2 = [];
@@ -2715,7 +2716,7 @@ module.exports = (function() {
         s5 = peg$parseeolChar();
         peg$silentFails--;
         if (s5 === peg$FAILED) {
-          s4 = peg$c1;
+          s4 = peg$c18;
         } else {
           peg$currPos = s4;
           s4 = peg$c0;
@@ -2726,7 +2727,7 @@ module.exports = (function() {
             peg$currPos++;
           } else {
             s5 = peg$FAILED;
-            if (peg$silentFails === 0) { peg$fail(peg$c83); }
+            if (peg$silentFails === 0) { peg$fail(peg$c84); }
           }
           if (s5 !== peg$FAILED) {
             s4 = [s4, s5];
@@ -2747,7 +2748,7 @@ module.exports = (function() {
           s5 = peg$parseeolChar();
           peg$silentFails--;
           if (s5 === peg$FAILED) {
-            s4 = peg$c1;
+            s4 = peg$c18;
           } else {
             peg$currPos = s4;
             s4 = peg$c0;
@@ -2758,7 +2759,7 @@ module.exports = (function() {
               peg$currPos++;
             } else {
               s5 = peg$FAILED;
-              if (peg$silentFails === 0) { peg$fail(peg$c83); }
+              if (peg$silentFails === 0) { peg$fail(peg$c84); }
             }
             if (s5 !== peg$FAILED) {
               s4 = [s4, s5];
@@ -2791,28 +2792,28 @@ module.exports = (function() {
       var s0, s1, s2, s3, s4, s5;
 
       s0 = peg$currPos;
-      if (input.substr(peg$currPos, 2) === peg$c124) {
-        s1 = peg$c124;
+      if (input.substr(peg$currPos, 2) === peg$c125) {
+        s1 = peg$c125;
         peg$currPos += 2;
       } else {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c125); }
+        if (peg$silentFails === 0) { peg$fail(peg$c126); }
       }
       if (s1 !== peg$FAILED) {
         s2 = [];
         s3 = peg$currPos;
         s4 = peg$currPos;
         peg$silentFails++;
-        if (input.substr(peg$currPos, 2) === peg$c126) {
-          s5 = peg$c126;
+        if (input.substr(peg$currPos, 2) === peg$c127) {
+          s5 = peg$c127;
           peg$currPos += 2;
         } else {
           s5 = peg$FAILED;
-          if (peg$silentFails === 0) { peg$fail(peg$c127); }
+          if (peg$silentFails === 0) { peg$fail(peg$c128); }
         }
         peg$silentFails--;
         if (s5 === peg$FAILED) {
-          s4 = peg$c1;
+          s4 = peg$c18;
         } else {
           peg$currPos = s4;
           s4 = peg$c0;
@@ -2823,7 +2824,7 @@ module.exports = (function() {
             peg$currPos++;
           } else {
             s5 = peg$FAILED;
-            if (peg$silentFails === 0) { peg$fail(peg$c83); }
+            if (peg$silentFails === 0) { peg$fail(peg$c84); }
           }
           if (s5 !== peg$FAILED) {
             s4 = [s4, s5];
@@ -2841,16 +2842,16 @@ module.exports = (function() {
           s3 = peg$currPos;
           s4 = peg$currPos;
           peg$silentFails++;
-          if (input.substr(peg$currPos, 2) === peg$c126) {
-            s5 = peg$c126;
+          if (input.substr(peg$currPos, 2) === peg$c127) {
+            s5 = peg$c127;
             peg$currPos += 2;
           } else {
             s5 = peg$FAILED;
-            if (peg$silentFails === 0) { peg$fail(peg$c127); }
+            if (peg$silentFails === 0) { peg$fail(peg$c128); }
           }
           peg$silentFails--;
           if (s5 === peg$FAILED) {
-            s4 = peg$c1;
+            s4 = peg$c18;
           } else {
             peg$currPos = s4;
             s4 = peg$c0;
@@ -2861,7 +2862,7 @@ module.exports = (function() {
               peg$currPos++;
             } else {
               s5 = peg$FAILED;
-              if (peg$silentFails === 0) { peg$fail(peg$c83); }
+              if (peg$silentFails === 0) { peg$fail(peg$c84); }
             }
             if (s5 !== peg$FAILED) {
               s4 = [s4, s5];
@@ -2876,12 +2877,12 @@ module.exports = (function() {
           }
         }
         if (s2 !== peg$FAILED) {
-          if (input.substr(peg$currPos, 2) === peg$c126) {
-            s3 = peg$c126;
+          if (input.substr(peg$currPos, 2) === peg$c127) {
+            s3 = peg$c127;
             peg$currPos += 2;
           } else {
             s3 = peg$FAILED;
-            if (peg$silentFails === 0) { peg$fail(peg$c127); }
+            if (peg$silentFails === 0) { peg$fail(peg$c128); }
           }
           if (s3 !== peg$FAILED) {
             s1 = [s1, s2, s3];
@@ -2907,43 +2908,43 @@ module.exports = (function() {
 
       peg$silentFails++;
       if (input.charCodeAt(peg$currPos) === 10) {
-        s0 = peg$c129;
+        s0 = peg$c130;
         peg$currPos++;
       } else {
         s0 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c130); }
+        if (peg$silentFails === 0) { peg$fail(peg$c131); }
       }
       if (s0 === peg$FAILED) {
-        if (input.substr(peg$currPos, 2) === peg$c131) {
-          s0 = peg$c131;
+        if (input.substr(peg$currPos, 2) === peg$c132) {
+          s0 = peg$c132;
           peg$currPos += 2;
         } else {
           s0 = peg$FAILED;
-          if (peg$silentFails === 0) { peg$fail(peg$c132); }
+          if (peg$silentFails === 0) { peg$fail(peg$c133); }
         }
         if (s0 === peg$FAILED) {
           if (input.charCodeAt(peg$currPos) === 13) {
-            s0 = peg$c133;
+            s0 = peg$c134;
             peg$currPos++;
           } else {
             s0 = peg$FAILED;
-            if (peg$silentFails === 0) { peg$fail(peg$c134); }
+            if (peg$silentFails === 0) { peg$fail(peg$c135); }
           }
           if (s0 === peg$FAILED) {
             if (input.charCodeAt(peg$currPos) === 8232) {
-              s0 = peg$c135;
+              s0 = peg$c136;
               peg$currPos++;
             } else {
               s0 = peg$FAILED;
-              if (peg$silentFails === 0) { peg$fail(peg$c136); }
+              if (peg$silentFails === 0) { peg$fail(peg$c137); }
             }
             if (s0 === peg$FAILED) {
               if (input.charCodeAt(peg$currPos) === 8233) {
-                s0 = peg$c137;
+                s0 = peg$c138;
                 peg$currPos++;
               } else {
                 s0 = peg$FAILED;
-                if (peg$silentFails === 0) { peg$fail(peg$c138); }
+                if (peg$silentFails === 0) { peg$fail(peg$c139); }
               }
             }
           }
@@ -2952,7 +2953,7 @@ module.exports = (function() {
       peg$silentFails--;
       if (s0 === peg$FAILED) {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c128); }
+        if (peg$silentFails === 0) { peg$fail(peg$c129); }
       }
 
       return s0;
@@ -2961,12 +2962,12 @@ module.exports = (function() {
     function peg$parseeolChar() {
       var s0;
 
-      if (peg$c139.test(input.charAt(peg$currPos))) {
+      if (peg$c140.test(input.charAt(peg$currPos))) {
         s0 = input.charAt(peg$currPos);
         peg$currPos++;
       } else {
         s0 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c140); }
+        if (peg$silentFails === 0) { peg$fail(peg$c141); }
       }
 
       return s0;
@@ -2976,17 +2977,17 @@ module.exports = (function() {
       var s0, s1;
 
       peg$silentFails++;
-      if (peg$c142.test(input.charAt(peg$currPos))) {
+      if (peg$c143.test(input.charAt(peg$currPos))) {
         s0 = input.charAt(peg$currPos);
         peg$currPos++;
       } else {
         s0 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c143); }
+        if (peg$silentFails === 0) { peg$fail(peg$c144); }
       }
       peg$silentFails--;
       if (s0 === peg$FAILED) {
         s1 = peg$FAILED;
-        if (peg$silentFails === 0) { peg$fail(peg$c141); }
+        if (peg$silentFails === 0) { peg$fail(peg$c142); }
       }
 
       return s0;
diff --git a/spec/compiler/passes/generate-bytecode.spec.js b/spec/compiler/passes/generate-bytecode.spec.js
index 829b78b..d9a1e4e 100644
--- a/spec/compiler/passes/generate-bytecode.spec.js
+++ b/spec/compiler/passes/generate-bytecode.spec.js
@@ -477,7 +477,7 @@ describe("compiler pass |generateBytecode|", function() {
 
     it("defines correct constants", function() {
       expect(pass).toChangeAST(grammar, constsDetails([
-        '""',
+        'null',
         '"a"',
         '{ type: "literal", value: "a", description: "\\"a\\"" }'
       ]));
diff --git a/spec/generated-parser.spec.js b/spec/generated-parser.spec.js
index f1912d4..c0fcff1 100644
--- a/spec/generated-parser.spec.js
+++ b/spec/generated-parser.spec.js
@@ -621,7 +621,7 @@ describe("generated parser", function() {
       it("matches correctly", function() {
         var parser = PEG.buildParser('start = "a"?', options);
 
-        expect(parser).toParse("",  "");
+        expect(parser).toParse("",  null);
         expect(parser).toParse("a", "a");
       });
     });
@@ -1112,8 +1112,8 @@ describe("generated parser", function() {
          */
         var parser = PEG.buildParser([
               'S = &(A "c") a:"a"+ B:B !("a" / "b" / "c") { return a.join("") + B; }',
-              'A = a:"a" A:A? b:"b" { return a + A + b; }',
-              'B = b:"b" B:B? c:"c" { return b + B + c; }'
+              'A = a:"a" A:A? b:"b" { return [a, A, b].join(""); }',
+              'B = b:"b" B:B? c:"c" { return [b, B, c].join(""); }'
             ].join("\n"), options);
 
         expect(parser).toParse("abc",       "abc");
diff --git a/src/parser.pegjs b/src/parser.pegjs
index dba4f37..e5d20e1 100644
--- a/src/parser.pegjs
+++ b/src/parser.pegjs
@@ -6,7 +6,7 @@ grammar
   = __ initializer:initializer? rules:rule+ {
       return {
         type:        "grammar",
-        initializer: initializer !== "" ? initializer : null,
+        initializer: initializer,
         rules:       rules
       };
     }
@@ -24,7 +24,7 @@ rule
       return {
         type:        "rule",
         name:        name,
-        expression:  displayName !== ""
+        expression:  displayName !== null
           ? {
               type:       "named",
               name:       displayName,
@@ -249,10 +249,10 @@ class "character class"
   = "[" inverted:"^"? parts:(classCharacterRange / classCharacter)* "]" flags:"i"? __ {
       var partsConverted = utils.map(parts, function(part) { return part.data; });
       var rawText = "["
-        + inverted
+        + (inverted !== null ? inverted : "")
         + utils.map(parts, function(part) { return part.rawText; }).join("")
         + "]"
-        + flags;
+        + (flags !== null ? flags : "");
 
       return {
         type:       "class",