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