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test/fixedbugs/issue13162.go
82 строки
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Martin Möhrmann
cmd/compile: improve string iteration performance
30 авг 2016, 21:17
30 авг 2016, 21:17
0dae9df
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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) }