slightly nicer implementation of SplatNode.compileSplattedArray

lib/helpers.js

@@ -1,5 +1,5 @@
 (function(){
-  var compact, count, del, extend, flatten, helpers, include, indexOf, merge, starts;
+  var compact, count, del, ends, extend, flatten, helpers, include, indexOf, merge, starts;
   var __hasProp = Object.prototype.hasOwnProperty;
   if (!(typeof process !== "undefined" && process !== null)) {
     this.exports = this;
@@ -25,6 +25,11 @@
   helpers.starts = (starts = function(string, literal, start) {
     return string.substring(start, (start || 0) + literal.length) === literal;
   });
+  helpers.ends = (ends = function(string, literal, back) {
+    var start;
+    start = string.length - literal.length - ((typeof back !== "undefined" && back !== null) ? back : 0);
+    return string.substring(start, start + literal.length) === literal;
+  });
   helpers.compact = (compact = function(array) {
     var _a, _b, _c, _d, item;
     _a = []; _c = array;

lib/nodes.js

@@ -1,5 +1,5 @@
 (function(){
-  var AccessorNode, ArrayNode, AssignNode, BaseNode, CallNode, ClassNode, ClosureNode, CodeNode, CommentNode, DOUBLE_PARENS, ExistenceNode, Expressions, ExtendsNode, ForNode, IDENTIFIER, IS_STRING, IfNode, InNode, IndexNode, LiteralNode, NUMBER, ObjectNode, OpNode, ParentheticalNode, PushNode, RangeNode, ReturnNode, Scope, SliceNode, SplatNode, TAB, TRAILING_WHITESPACE, ThrowNode, TryNode, UTILITIES, ValueNode, WhileNode, _a, compact, del, flatten, helpers, include, indexOf, literal, merge, starts, utility;
+  var AccessorNode, ArrayNode, AssignNode, BaseNode, CallNode, ClassNode, ClosureNode, CodeNode, CommentNode, DOUBLE_PARENS, ExistenceNode, Expressions, ExtendsNode, ForNode, IDENTIFIER, IS_STRING, IfNode, InNode, IndexNode, LiteralNode, NUMBER, ObjectNode, OpNode, ParentheticalNode, PushNode, RangeNode, ReturnNode, Scope, SliceNode, SplatNode, TAB, TRAILING_WHITESPACE, ThrowNode, TryNode, UTILITIES, ValueNode, WhileNode, _a, compact, del, ends, flatten, helpers, include, indexOf, literal, merge, starts, utility;
   var __extends = function(child, parent) {
     var ctor = function(){ };
     ctor.prototype = parent.prototype;
@@ -23,6 +23,7 @@
   include = _a.include;
   indexOf = _a.indexOf;
   starts = _a.starts;
+  ends = _a.ends;
   exports.BaseNode = (function() {
     BaseNode = function() {    };
     BaseNode.prototype.compile = function(o) {
@@ -419,7 +420,7 @@
       this.variable = this.isSuper ? null : variable;
       this.args = (args || []);
       this.compileSplatArguments = function(o) {
-        return SplatNode.compileMixedArray.call(this, this.args, o);
+        return SplatNode.compileSplattedArray.call(this, this.args, o);
       };
       return this;
     };
@@ -670,7 +671,7 @@
     ArrayNode = function(objects) {
       this.objects = objects || [];
       this.compileSplatLiteral = function(o) {
-        return SplatNode.compileMixedArray.call(this, this.objects, o);
+        return SplatNode.compileSplattedArray.call(this, this.objects, o);
       };
       return this;
     };
@@ -1015,28 +1016,26 @@
       trail = trailings ? (", " + (name) + ".length - " + trailings) : '';
       return "" + (utility('slice')) + ".call(" + name + ", " + index + trail + ")";
     };
-    SplatNode.compileMixedArray = function(list, o) {
-      var _b, _c, _d, arg, args, code, i, prev;
+    SplatNode.compileSplattedArray = function(list, o) {
+      var _b, _c, arg, args, code, i, last, prev;
       args = [];
-      i = 0;
-      _c = list;
-      for (_b = 0, _d = _c.length; _b < _d; _b++) {
-        arg = _c[_b];
+      _b = list;
+      for (i = 0, _c = _b.length; i < _c; i++) {
+        arg = _b[i];
         code = arg.compile(o);
+        prev = args[(last = args.length - 1)];
         if (!(arg instanceof SplatNode)) {
-          prev = args[i - 1];
-          if (i === 1 && prev.substr(0, 1) === '[' && prev.substr(prev.length - 1, 1) === ']') {
-            args[i - 1] = ("" + (prev.substr(0, prev.length - 1)) + ", " + code + "]");
+          if (prev && starts(prev, '[') && ends(prev, ']')) {
+            args[last] = ("" + (prev.substr(0, prev.length - 1)) + ", " + code + "]");
             continue;
-          } else if (i > 1 && prev.substr(0, 9) === '.concat([' && prev.substr(prev.length - 2, 2) === '])') {
-            args[i - 1] = ("" + (prev.substr(0, prev.length - 2)) + ", " + code + "])");
+          } else if (prev && starts(prev, '.concat([') && ends(prev, '])')) {
+            args[last] = ("" + (prev.substr(0, prev.length - 2)) + ", " + code + "])");
             continue;
           } else {
             code = ("[" + code + "]");
           }
         }
         args.push(i === 0 ? code : (".concat(" + code + ")"));
-        i += 1;
       }
       return args.join('');
     };

src/helpers.coffee

@@ -22,6 +22,11 @@ helpers.include: include: (list, value) ->
 helpers.starts: starts: (string, literal, start) ->
   string.substring(start, (start or 0) + literal.length) is literal
 
+# Peek at the end of a given string to see if it matches a sequence.
+helpers.ends: ends: (string, literal, back) ->
+  start: string.length - literal.length - (back ? 0)
+  string.substring(start, start + literal.length) is literal
+
 # Trim out all falsy values from an array.
 helpers.compact: compact: (array) -> item for item in array when item
 

src/nodes.coffee

@@ -14,7 +14,7 @@ else
   Scope:        this.Scope
 
 # Import the helpers we plan to use.
-{compact, flatten, merge, del, include, indexOf, starts}: helpers
+{compact, flatten, merge, del, include, indexOf, starts, ends}: helpers
 
 #### BaseNode
 
@@ -403,7 +403,7 @@ exports.CallNode: class CallNode extends BaseNode
     @variable:  if @isSuper then null else variable
     @args:      (args or [])
     @compileSplatArguments: (o) ->
-      SplatNode.compileMixedArray.call(this, @args, o)
+      SplatNode.compileSplattedArray.call(this, @args, o)
 
   # Tag this invocation as creating a new instance.
   newInstance: ->
@@ -625,7 +625,7 @@ exports.ArrayNode: class ArrayNode extends BaseNode
   constructor: (objects) ->
     @objects: objects or []
     @compileSplatLiteral: (o) ->
-      SplatNode.compileMixedArray.call(this, @objects, o)
+      SplatNode.compileSplattedArray.call(this, @objects, o)
 
   compileNode: (o) ->
     o.indent: @idt 1
@@ -921,23 +921,21 @@ exports.SplatNode: class SplatNode extends BaseNode
 
   # Utility function that converts arbitrary number of elements, mixed with
   # splats, to a proper array
-  @compileMixedArray: (list, o) ->
+  @compileSplattedArray: (list, o) ->
     args: []
-    i: 0
-    for arg in list
+    for arg, i in list
       code: arg.compile o
+      prev: args[last: args.length - 1]
       if not (arg instanceof SplatNode)
-        prev: args[i - 1]
-        if i is 1 and prev.substr(0, 1) is '[' and prev.substr(prev.length - 1, 1) is ']'
-          args[i - 1]: "${prev.substr(0, prev.length - 1)}, $code]"
+        if prev and starts(prev, '[') and ends(prev, ']')
+          args[last]: "${prev.substr(0, prev.length - 1)}, $code]"
           continue
-        else if i > 1 and prev.substr(0, 9) is '.concat([' and prev.substr(prev.length - 2, 2) is '])'
-          args[i - 1]: "${prev.substr(0, prev.length - 2)}, $code])"
+        else if prev and starts(prev, '.concat([') and ends(prev, '])')
+          args[last]: "${prev.substr(0, prev.length - 2)}, $code])"
           continue
         else
           code: "[$code]"
       args.push(if i is 0 then code else ".concat($code)")
-      i: + 1
     args.join('')
 
 #### WhileNode

test/test_splats.coffee

@@ -105,3 +105,11 @@ ok pen is 2
 
 method 1, 2
 ok pen is 2
+
+
+# Array splat expansions with assigns.
+nums: [1, 2, 3]
+list: [a: 0, nums..., b: 4]
+ok a is 0
+ok b is 4
+ok list.join(' ') is '0 1 2 3 4'