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83 lines
1.6 KiB
83 lines
1.6 KiB
// run
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// Copyright 2016 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Ensure that range loops over a string have the requisite side-effects.
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package main
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import (
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"fmt"
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"os"
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)
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func check(n int) {
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var i int
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var r rune
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b := make([]byte, n)
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for i = range b {
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b[i] = byte(i + 1)
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}
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s := string(b)
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// When n == 0, i is untouched by the range loop.
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// Picking an initial value of -1 for i makes the
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// "want" calculation below correct in all cases.
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i = -1
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for i = range s {
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b[i] = s[i]
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}
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if want := n - 1; i != want {
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fmt.Printf("index after range with side-effect = %d want %d\n", i, want)
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os.Exit(1)
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}
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i = -1
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r = '\x00'
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for i, r = range s {
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b[i] = byte(r)
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}
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if want := n - 1; i != want {
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fmt.Printf("index after range with side-effect = %d want %d\n", i, want)
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os.Exit(1)
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}
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if want := rune(n); r != want {
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fmt.Printf("rune after range with side-effect = %q want %q\n", r, want)
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os.Exit(1)
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}
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i = -1
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// i is shadowed here, so its value should be unchanged.
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for i := range s {
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b[i] = s[i]
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}
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if want := -1; i != want {
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fmt.Printf("index after range without side-effect = %d want %d\n", i, want)
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os.Exit(1)
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}
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i = -1
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r = -1
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// i and r are shadowed here, so their values should be unchanged.
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for i, r := range s {
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b[i] = byte(r)
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}
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if want := -1; i != want {
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fmt.Printf("index after range without side-effect = %d want %d\n", i, want)
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os.Exit(1)
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}
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if want := rune(-1); r != want {
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fmt.Printf("rune after range without side-effect = %q want %q\n", r, want)
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os.Exit(1)
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}
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}
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func main() {
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check(0)
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check(1)
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check(15)
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}
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