rearrange builtins

builtins/bool.go

@@ -0,0 +1,40 @@
+package builtins
+
+import "monkey/object"
+
+// Bool ...
+func Bool(args ...object.Object) object.Object {
+	if len(args) != 1 {
+		return newError("wrong number of arguments. got=%d, want=1", len(args))
+	}
+
+	switch arg := args[0].(type) {
+	case *object.Null:
+		return &object.Boolean{Value: false}
+	case *object.Boolean:
+		return arg
+	case *object.Integer:
+		if arg.Value == 0 {
+			return &object.Boolean{Value: false}
+		}
+		return &object.Boolean{Value: true}
+	case *object.String:
+		if len(arg.Value) > 0 {
+			return &object.Boolean{Value: true}
+		}
+		return &object.Boolean{Value: false}
+	case *object.Array:
+		if len(arg.Elements) > 0 {
+			return &object.Boolean{Value: true}
+		}
+		return &object.Boolean{Value: false}
+	case *object.Hash:
+		if len(arg.Pairs) > 0 {
+			return &object.Boolean{Value: true}
+		}
+		return &object.Boolean{Value: false}
+
+	default:
+		return newError("argument to `bool` not supported, got=%s", args[0].Type())
+	}
+}