問題描述

當(dāng)我嘗試在 gcc 4.8.2 中編譯以下代碼時，出現(xiàn)以下錯誤:

test.cc: 在函數(shù)‘void foo(int*)’中:test.cc:15:16: 錯誤:沒有匹配的函數(shù)調(diào)用‘begin(int*&)’for (int i : bar) {^

以及來自模板庫深處的其他一些人.

#include 使用命名空間標(biāo)準(zhǔn)；void foo(int*);int main() {int bar[3] = {1,2,3};for (int i : bar) {cout<<我＜＜結(jié)束;}富(酒吧)；}void foo(int* bar) {for (int i : bar) {cout<<我＜＜結(jié)束;}}

如果我重新定義 foo 以使用索引的 for 循環(huán)，那么代碼會編譯并按預(yù)期運行.此外，如果我將基于范圍的輸出循環(huán)移動到 main 中，我也會得到預(yù)期的行為.

如何將數(shù)組 bar 傳遞給 foo 使其能夠在其上執(zhí)行基于范圍的 for 循環(huán)?

隨著數(shù)組衰減變成一個指針，你'丟失了一條重要信息:它的大小.

使用數(shù)組引用，您的基于范圍的循環(huán)可以工作:

void foo(int (&bar)[3]);int main() {int bar[3] = {1,2,3};for (int i : bar) {cout<<我＜＜結(jié)束;}富(酒吧)；}void foo(int (&bar)[3]) {for (int i : bar) {cout<<我＜＜結(jié)束;}}

或者，以通用方式(即在函數(shù)簽名中不指定數(shù)組大小)，

模板void foo(int (&bar)[array_size]) {for (int i : bar) {cout<<我＜＜結(jié)束;}}

試試

When I try to compile the following code in gcc 4.8.2, I get the following error:

test.cc: In function ‘void foo(int*)’:
test.cc:15:16: error: no matching function for call to ‘begin(int*&)’
   for (int i : bar) {
                ^

Along with a bunch of others from deeper in the template library.

#include <iostream>
using namespace std;

void foo(int*);

int main() {
  int bar[3] = {1,2,3};
  for (int i : bar) {
    cout << i << endl;
  }
  foo(bar);
}

void foo(int* bar) {
  for (int i : bar) {
    cout << i << endl;
  }
}

If I redefine foo to use an indexed for loop, then the code compiles and behaves as expected. Also, if I move the range-based output loop into main, I get the expected behaviour as well.

How do I pass the array bar to foo in such a way that it is capable of executing a range-based for-loop on it?

With the array decaying into a pointer you're losing one important piece of information: its size.

With an array reference your range based loop works:

void foo(int (&bar)[3]);

int main() {
  int bar[3] = {1,2,3};
  for (int i : bar) {
    cout << i << endl;
  }
  foo(bar);
}

void foo(int (&bar)[3]) {
  for (int i : bar) {
    cout << i << endl;
  }
}

or, in a generic fashion (i.e. without specifying the array size in the function signature),

template <std::size_t array_size>
void foo(int (&bar)[array_size]) {
  for (int i : bar) {
    cout << i << endl;
  }
}

Try it out

這篇關(guān)于傳遞給非主函數(shù)的數(shù)組上基于范圍的 for 循環(huán)的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網(wǎng)！