go/test/typeswitch1.go

// $G $D/$F.go && $L $F.$A && ./$A.out

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package main

import "fmt"

const (
	a = iota;
	b;
	c;
	d;
	e;
)

var x = []int{1,2,3}

func f(x int, len *byte) {
	*len = byte(x);
}

func whatis(x interface{}) string {
	switch xx := x.(type) {
	default:
		return fmt.Sprint("default ", xx);
	case int, int8, int16, int32:
		return fmt.Sprint("signed ", xx);
	case int64:
		return fmt.Sprint("signed64 ", int64(xx));
	case uint, uint8, uint16, uint32:
		return fmt.Sprint("unsigned ", xx);
	case uint64:
		return fmt.Sprint("unsigned64 ", uint64(xx));
	case nil:
		return fmt.Sprint("nil ", xx);
	}
	panic("not reached");
}

func whatis1(x interface{}) string {
	xx := x;
	switch xx.(type) {
	default:
		return fmt.Sprint("default ", xx);
	case int, int8, int16, int32:
		return fmt.Sprint("signed ", xx);
	case int64:
		return fmt.Sprint("signed64 ", xx.(int64));
	case uint, uint8, uint16, uint32:
		return fmt.Sprint("unsigned ", xx);
	case uint64:
		return fmt.Sprint("unsigned64 ", xx.(uint64));
	case nil:
		return fmt.Sprint("nil ", xx);
	}
	panic("not reached");
}

func check(x interface{}, s string) {
	w := whatis(x);
	if w != s {
		fmt.Println("whatis", x, "=>", w, "!=", s);
		panic();
	}

	w = whatis1(x);
	if w != s {
		fmt.Println("whatis1", x, "=>", w, "!=", s);
		panic();
	}
}

func main() {
	check(1, "signed 1");
	check(uint(1), "unsigned 1");
	check(int64(1), "signed64 1");
	check(uint64(1), "unsigned64 1");
	check(1.5, "default 1.5");
	check(nil, "nil <nil>");
}