more builtins

builtins/pow.go

@@ -0,0 +1,34 @@
+package builtins
+
+import "monkey/object"
+
+func pow(x, y int64) int64 {
+	p := int64(1)
+	for y > 0 {
+		if y&1 != 0 {
+			p *= x
+		}
+		y >>= 1
+		x *= x
+	}
+	return p
+}
+
+// Pow ...
+func Pow(args ...object.Object) object.Object {
+	if len(args) != 2 {
+		return newError("wrong number of arguments. got=%d, want=2",
+			len(args))
+	}
+
+	if x, ok := args[0].(*object.Integer); ok {
+		if y, ok := args[1].(*object.Integer); ok {
+			value := pow(x.Value, y.Value)
+			return &object.Integer{Value: value}
+		} else {
+			return newError("expected argument #2 to `pow` to be `int` got=%s", args[1].Type())
+		}
+	} else {
+		return newError("expected argument #1 to `pow` to be `int` got=%s", args[0].Type())
+	}
+}