Implement xrange.__len__. (#159)

runtime/range.go

@@ -182,6 +182,11 @@ func xrangeIter(f *Frame, o *Object) (*Object, *BaseException) {
 	return &(&rangeIterator{Object{typ: rangeIteratorType}, r.start, r.stop, r.step}).Object, nil
 }
 
+func xrangeLen(f *Frame, o *Object) (*Object, *BaseException) {
+	r := toXRangeUnsafe(o)
+	return NewInt((r.stop - r.start) / r.step).ToObject(), nil
+}
+
 func xrangeNew(f *Frame, _ *Type, args Args, _ KWArgs) (*Object, *BaseException) {
 	expectedTypes := []*Type{IntType, IntType, IntType}
 	argc := len(args)
@@ -229,6 +234,7 @@ func initXRangeType(map[string]*Object) {
 	xrangeType.flags &^= typeFlagBasetype
 	xrangeType.slots.GetItem = &binaryOpSlot{xrangeGetItem}
 	xrangeType.slots.Iter = &unaryOpSlot{xrangeIter}
+	xrangeType.slots.Len = &unaryOpSlot{xrangeLen}
 	xrangeType.slots.New = &newSlot{xrangeNew}
 	xrangeType.slots.Repr = &unaryOpSlot{xrangeRepr}
 }

runtime/range_test.go

@@ -85,6 +85,20 @@ func TestXRangeGetItem(t *testing.T) {
 	}
 }
 
+func TestXRangeLen(t *testing.T) {
+	cases := []invokeTestCase{
+		{args: wrapArgs(newTestXRange(10)), want: NewInt(10).ToObject()},
+		{args: wrapArgs(newTestXRange(10, 12)), want: NewInt(2).ToObject()},
+		{args: wrapArgs(newTestXRange(5, 16, 5)), want: NewInt(3).ToObject()},
+		{args: wrapArgs(newTestXRange(5, -2, -3)), want: NewInt(3).ToObject()},
+	}
+	for _, cas := range cases {
+		if err := runInvokeMethodTestCase(xrangeType, "__len__", &cas); err != "" {
+			t.Error(err)
+		}
+	}
+}
+
 func TestXRangeNew(t *testing.T) {
 	fun := newBuiltinFunction("TestXRangeNew", func(f *Frame, args Args, _ KWArgs) (*Object, *BaseException) {
 		xrange, raised := xrangeType.Call(f, args, nil)