more builtins

builtins/abs.go

@@ -0,0 +1,20 @@
+package builtins
+
+import "monkey/object"
+
+// Abs  ...
+func Abs(args ...object.Object) object.Object {
+	if len(args) != 1 {
+		return newError("wrong number of arguments. got=%d, want=1",
+			len(args))
+	}
+
+	if i, ok := args[0].(*object.Integer); ok {
+		value := i.Value
+		if value < 0 {
+			value = value * -1
+		}
+		return &object.Integer{Value: value}
+	}
+	return newError("argument to `abs` not supported, got %s", args[0].Type())
+}