Implement .reduce() and .reduceRight() on typed arrays

src/harmony-typedarray.js

Index: src/harmony-typedarray.js
diff --git a/src/harmony-typedarray.js b/src/harmony-typedarray.js
index 014206c4cba8400cf745b9295d5cb223695ad6cb..17f72950ddeb57e59801ca817e0ca6bd22741766 100644
--- a/src/harmony-typedarray.js
+++ b/src/harmony-typedarray.js
@@ -69,6 +69,90 @@ function NAMEOf() {  // length == 0
   return array;
 }
 
+// ES6 draft 10-14-14, section 22.2.3.19
+function NAMEReduce(f /* initialValue */) {  // length == 1
+  if (!%IsTypedArray(this)) {
+    throw MakeTypeError('not_typed_array');
+  }
+  if (!IS_SPEC_FUNCTION(f)) {
+    throw MakeTypeError('called_non_callable', [ f ]);
+  }
+
+  var length = %_TypedArrayGetLength(this);
+  var accumulator;
+  var i;
+
+  if (%_ArgumentsLength() > 1) {
+    accumulator = %_Arguments(1);
+    i = 0;
+  } else if (length == 0) {
+    throw MakeTypeError('reduce_no_initial', []);
+  } else {
+    accumulator = this[0];
+    i = 1;
+  }
+
+  var receiver = %GetDefaultReceiver(f);
+  var needs_wrapper = false;
+  if (IS_NULL_OR_UNDEFINED(receiver)) {
+    receiver = %GetDefaultReceiver(f) || receiver;
+  } else {
+    needs_wrapper = SHOULD_CREATE_WRAPPER(f, receiver);
+  }
+
+  var stepping = DEBUG_IS_ACTIVE && %DebugCallbackSupportsStepping(f);
+  for (; i < length; i++) {
+    var element = this[i];
+    // Prepare break slots for debugger step in.
+    if (stepping) %DebugPrepareStepInIfStepping(f);
+    var new_receiver = needs_wrapper ? ToObject(receiver) : receiver;
+    accumulator = %_CallFunction(receiver, accumulator, element, i, this, f);
+  }
+  return accumulator;
+}
+
+// ES6 draft 10-14-14, section 22.2.3.20
+function NAMEReduceRight(f /* initialValue */) {  // length == 1
+  if (!%IsTypedArray(this)) {
+    throw MakeTypeError('not_typed_array', []);
+  }
+  if (!IS_SPEC_FUNCTION(f)) {
+    throw MakeTypeError('called_non_callable', [ f ]);
+  }
+
+  var length = %_TypedArrayGetLength(this);
+  var accumulator;
+  var i;
+
+  if (%_ArgumentsLength() > 1) {
+    accumulator = %_Arguments(1);
+    i = length - 1;
+  } else if (length == 0) {
+    throw MakeTypeError('reduce_no_initial', []);
+  } else {
+    i = length - 1;
+    accumulator = this[i--];
+  }
+
+  var receiver = %GetDefaultReceiver(f);
+  var needs_wrapper = false;
+  if (IS_NULL_OR_UNDEFINED(receiver)) {
+    receiver = %GetDefaultReceiver(f) || receiver;
+  } else {
+    needs_wrapper = SHOULD_CREATE_WRAPPER(f, receiver);
+  }
+
+  var stepping = DEBUG_IS_ACTIVE && %DebugCallbackSupportsStepping(f);
+  for (; i >= 0; i--) {
+    var element = this[i];
+    // Prepare break slots for debugger step in.
+    if (stepping) %DebugPrepareStepInIfStepping(f);
+    var new_receiver = needs_wrapper ? ToObject(receiver) : receiver;
+    accumulator = %_CallFunction(receiver, accumulator, element, i, this, f);
+  }
+  return accumulator;
+}
+
 endmacro
 
 TYPED_ARRAYS(TYPED_ARRAY_HARMONY_ADDITIONS)
@@ -84,8 +168,10 @@ macro EXTEND_TYPED_ARRAY(ARRAY_ID, NAME, ELEMENT_SIZE)
   ));
 
   // Set up non-enumerable functions on the prototype object.
-  InstallFunctions(global.NAME.prototype, DONT_ENUM, $Array(
-    "forEach", NAMEForEach
+  InstallFunctions(global.NAME.prototype, DONT_ENUM | DONT_DELETE | READ_ONLY, $Array(
+    "forEach", NAMEForEach,
+    "reduce", NAMEReduce,
+    "reduceRight", NAMEReduceRight
   ));
 endmacro