Added splats positional flexibility to pattern matching

lib/nodes.js

@@ -934,12 +934,13 @@
     // See the [ECMAScript Harmony Wiki](http://wiki.ecmascript.org/doku.php?id=harmony:destructuring)
     // for details.
     AssignNode.prototype.compile_pattern_match = function compile_pattern_match(o) {
-      var _a, _b, _c, access_class, assigns, code, i, idx, obj, val, val_var, value;
+      var _a, _b, _c, access_class, assigns, code, i, idx, obj, oindex, olength, splatted, val, val_var, value;
       val_var = o.scope.free_variable();
       value = this.value.is_statement() ? ClosureNode.wrap(this.value) : this.value;
       assigns = ['' + this.tab + val_var + " = " + (value.compile(o)) + ";"];
       o.top = true;
       o.as_statement = true;
+      splatted = false;
       _a = this.variable.base.objects;
       for (i = 0, _b = _a.length; i < _b; i++) {
         obj = _a[i];
@@ -950,12 +951,11 @@
           idx = _c[1];
         }
         access_class = this.variable.is_array() ? IndexNode : AccessorNode;
-        if (obj instanceof SplatNode) {
+        if (obj instanceof SplatNode && !splatted) {
-          val = literal(obj.compile_value(o, val_var, this.variable.base.objects.indexOf(obj)));
+          val = literal(obj.compile_value(o, val_var, ((oindex = this.variable.base.objects.indexOf(obj))), ((olength = this.variable.base.objects.length)) - oindex - 1));
+          splatted = true;
         } else {
-          if (!(typeof idx === 'object')) {
+          typeof idx !== 'object' ? splatted ? (idx = literal('' + (val_var) + ".length - " + (olength - idx))) : (idx = literal(idx)) : null;
-            idx = literal(idx);
-          }
           val = new ValueNode(literal(val_var), [new access_class(idx)]);
         }
         assigns.push(new AssignNode(obj, val).compile(o));
@@ -1123,8 +1123,12 @@
     };
     // A compiling a splat as a destructuring assignment means slicing arguments
     // from the right-hand-side's corresponding array.
-    SplatNode.prototype.compile_value = function compile_value(o, name, index) {
+    SplatNode.prototype.compile_value = function compile_value(o, name, index, trailings) {
-      return "Array.prototype.slice.call(" + name + ", " + index + ")";
+      if ((typeof trailings !== "undefined" && trailings !== null)) {
+        return "Array.prototype.slice.call(" + name + ", " + index + ", " + (name) + ".length - " + trailings + ")";
+      } else {
+        return "Array.prototype.slice.call(" + name + ", " + index + ")";
+      }
     };
     return SplatNode;
   }).call(this);

src/nodes.coffee

@@ -708,14 +708,21 @@ exports.AssignNode: class AssignNode extends BaseNode
     assigns: ["$@tab$val_var = ${ value.compile(o) };"]
     o.top: true
     o.as_statement: true
+    splatted: false
     for obj, i in @variable.base.objects
       idx: i
       [obj, idx]: [obj.value, obj.variable.base] if @variable.is_object()
       access_class: if @variable.is_array() then IndexNode else AccessorNode
-      if obj instanceof SplatNode
+      if obj instanceof SplatNode and not splatted
-        val: literal(obj.compile_value(o, val_var, @variable.base.objects.indexOf(obj)))
+        val: literal(obj.compile_value(o, val_var, (oindex: @variable.base.objects.indexOf(obj)), 
+          (olength: @variable.base.objects.length) - oindex - 1))
+        splatted: true
       else
-        idx: literal(idx) unless typeof idx is 'object'
+        if typeof idx isnt 'object'
+          if splatted
+            idx: literal("${val_var}.length - ${olength - idx}")
+          else
+            idx: literal(idx)
         val: new ValueNode(literal(val_var), [new access_class(idx)])
       assigns.push(new AssignNode(obj, val).compile(o))
     code: assigns.join("\n")
@@ -829,8 +836,9 @@ exports.SplatNode: class SplatNode extends BaseNode
 
   # A compiling a splat as a destructuring assignment means slicing arguments
   # from the right-hand-side's corresponding array.
-  compile_value: (o, name, index) ->
+  compile_value: (o, name, index, trailings) ->
-    "Array.prototype.slice.call($name, $index)"
+    if trailings? then "Array.prototype.slice.call($name, $index, ${name}.length - $trailings)" \
+    else "Array.prototype.slice.call($name, $index)"
 
 # Utility function that converts arbitrary number of elements, mixed with
 # splats, to a proper array

test/test_pattern_matching.coffee

@@ -28,6 +28,20 @@ ok a is 1
 ok b is 2
 ok c is 3
 
+[x,y...,z]: [1,2,3,4,5]
+
+ok x is 1
+ok y.length is 3
+ok z is 5
+
+[x, [y, mids..., last], z..., end]: [1, [10, 20, 30, 40], 2,3,4, 5]
+
+ok x is 1
+ok y is 10
+ok mids.length is 2 and mids[1] is 30
+ok last is 40
+ok z.length is 3 and z[2] is 4
+ok end is 5
 
 obj: {x: 10, y: 20, z: 30}