adding until loops as the inverse of while loops

lib/grammar.js

@@ -470,6 +470,15 @@
         return new WhileNode($2, {
           guard: $4
         });
+      }), o("UNTIL Expression", function() {
+        return new WhileNode($2, {
+          invert: true
+        });
+      }), o("UNTIL Expression WHEN Expression", function() {
+        return new WhileNode($2, {
+          invert: true,
+          guard: $4
+        });
       })
     ],
     // The while loop can either be normal, with a block of expressions to execute,
@@ -740,7 +749,7 @@
   //     2 + (3 * 4)
   // And not:
   //     (2 + 3) * 4
-  operators = [["left", '?'], ["nonassoc", 'UMINUS', 'UPLUS', '!', '!!', '~', '++', '--'], ["left", '*', '/', '%'], ["left", '+', '-'], ["left", '<<', '>>', '>>>'], ["left", '&', '|', '^'], ["left", '<=', '<', '>', '>='], ["right", 'DELETE', 'INSTANCEOF', 'TYPEOF'], ["left", '==', '!='], ["left", '&&', '||'], ["right", '-=', '+=', '/=', '*=', '%=', '||=', '&&=', '?='], ["left", '.'], ["right", 'INDENT'], ["left", 'OUTDENT'], ["right", 'WHEN', 'LEADING_WHEN', 'IN', 'OF', 'BY', 'THROW'], ["right", 'FOR', 'NEW', 'SUPER', 'CLASS'], ["left", 'EXTENDS'], ["right", 'ASSIGN', 'RETURN'], ["right", '->', '=>', '<-', 'UNLESS', 'IF', 'ELSE', 'WHILE']];
+  operators = [["left", '?'], ["nonassoc", 'UMINUS', 'UPLUS', '!', '!!', '~', '++', '--'], ["left", '*', '/', '%'], ["left", '+', '-'], ["left", '<<', '>>', '>>>'], ["left", '&', '|', '^'], ["left", '<=', '<', '>', '>='], ["right", 'DELETE', 'INSTANCEOF', 'TYPEOF'], ["left", '==', '!='], ["left", '&&', '||'], ["right", '-=', '+=', '/=', '*=', '%=', '||=', '&&=', '?='], ["left", '.'], ["right", 'INDENT'], ["left", 'OUTDENT'], ["right", 'WHEN', 'LEADING_WHEN', 'IN', 'OF', 'BY', 'THROW'], ["right", 'FOR', 'NEW', 'SUPER', 'CLASS'], ["left", 'EXTENDS'], ["right", 'ASSIGN', 'RETURN'], ["right", '->', '=>', '<-', 'UNLESS', 'IF', 'ELSE', 'WHILE', 'UNTIL']];
   // Wrapping Up
   // -----------
   // Finally, now what we have our **grammar** and our **operators**, we can create

lib/lexer.js

@@ -615,7 +615,7 @@
   // CoffeeScript-only keywords, which we're more relaxed about allowing. They can't
   // be used standalone, but you can reference them as an attached property.
   COFFEE_ALIASES = ["and", "or", "is", "isnt", "not"];
-  COFFEE_KEYWORDS = COFFEE_ALIASES.concat(["then", "unless", "yes", "no", "on", "off", "of", "by", "where", "when"]);
+  COFFEE_KEYWORDS = COFFEE_ALIASES.concat(["then", "unless", "until", "yes", "no", "on", "off", "of", "by", "where", "when"]);
   // The combined list of keywords is the superset that gets passed verbatim to
   // the parser.
   KEYWORDS = JS_KEYWORDS.concat(COFFEE_KEYWORDS);

lib/nodes.js

@@ -1176,6 +1176,9 @@
   // flexibility or more speed than a comprehension can provide.
   exports.WhileNode = (function() {
     WhileNode = function WhileNode(condition, opts) {
+      if (opts && opts.invert) {
+        condition = new OpNode('!', condition);
+      }
       this.children = [(this.condition = condition)];
       this.guard = opts && opts.guard;
       return this;

lib/rewriter.js

@@ -375,7 +375,7 @@
   // Tokens indicating that the implicit call must enclose a block of expressions.
   IMPLICIT_BLOCK = ['->', '=>', '{', '[', ','];
   // Tokens that always mark the end of an implicit call for single-liners.
-  IMPLICIT_END = ['IF', 'UNLESS', 'FOR', 'WHILE', 'TERMINATOR', 'INDENT'].concat(EXPRESSION_END);
+  IMPLICIT_END = ['IF', 'UNLESS', 'FOR', 'WHILE', 'UNTIL', 'TERMINATOR', 'INDENT'].concat(EXPRESSION_END);
   // Single-line flavors of block expressions that have unclosed endings.
   // The grammar can't disambiguate them, so we insert the implicit indentation.
   SINGLE_LINERS = ['ELSE', "->", "=>", 'TRY', 'FINALLY', 'THEN'];

src/grammar.coffee

@@ -414,6 +414,8 @@ grammar: {
   WhileSource: [
     o "WHILE Expression",                       -> new WhileNode $2
     o "WHILE Expression WHEN Expression",       -> new WhileNode $2, {guard : $4}
+    o "UNTIL Expression",                       -> new WhileNode $2, {invert: true}
+    o "UNTIL Expression WHEN Expression",       -> new WhileNode $2, {invert: true, guard: $4}
   ]
 
   # The while loop can either be normal, with a block of expressions to execute,
@@ -603,7 +605,7 @@ operators: [
   ["right",     'FOR', 'NEW', 'SUPER', 'CLASS']
   ["left",      'EXTENDS']
   ["right",     'ASSIGN', 'RETURN']
-  ["right",     '->', '=>', '<-', 'UNLESS', 'IF', 'ELSE', 'WHILE']
+  ["right",     '->', '=>', '<-', 'UNLESS', 'IF', 'ELSE', 'WHILE', 'UNTIL']
 ]
 
 # Wrapping Up

src/lexer.coffee

@@ -449,7 +449,7 @@ JS_KEYWORDS: [
 # be used standalone, but you can reference them as an attached property.
 COFFEE_ALIASES:  ["and", "or", "is", "isnt", "not"]
 COFFEE_KEYWORDS: COFFEE_ALIASES.concat [
-  "then", "unless",
+  "then", "unless", "until",
   "yes", "no", "on", "off",
   "of", "by", "where", "when"
 ]

src/nodes.coffee

@@ -855,6 +855,7 @@ exports.SplatNode: class SplatNode extends BaseNode
 exports.WhileNode: class WhileNode extends BaseNode
 
   constructor: (condition, opts) ->
+    condition: new OpNode('!', condition) if opts and opts.invert
     @children:[@condition: condition]
     @guard: opts and opts.guard
 

src/rewriter.coffee

@@ -283,7 +283,7 @@ IMPLICIT_CALL:  ['IDENTIFIER', 'NUMBER', 'STRING', 'JS', 'REGEX', 'NEW', 'PARAM_
 IMPLICIT_BLOCK: ['->', '=>', '{', '[', ',']
 
 # Tokens that always mark the end of an implicit call for single-liners.
-IMPLICIT_END:   ['IF', 'UNLESS', 'FOR', 'WHILE', 'TERMINATOR', 'INDENT'].concat EXPRESSION_END
+IMPLICIT_END:   ['IF', 'UNLESS', 'FOR', 'WHILE', 'UNTIL', 'TERMINATOR', 'INDENT'].concat EXPRESSION_END
 
 # Single-line flavors of block expressions that have unclosed endings.
 # The grammar can't disambiguate them, so we insert the implicit indentation.

test/test_while.coffee

@@ -28,3 +28,11 @@ results: while i -= 1 when i % 2 is 0
 
 ok results.join(' ') is '16 12 8 4'
 
+
+value: false
+i: 0
+results: until value
+  value: true if i is 5
+  i += 1
+
+ok i is 6