语法范围 [英] Range for syntax

问题描述

当我写这样的东西时:

int data[] = {10,44,56,78,8};      
int i = 0;
for(int element : data)
   ...

该 for 然后由编译器以常规的 for 翻译?是 for 只是语法糖?

that for is then translated by the compiler in a regular for? is that for only a syntactic sugar?

推荐答案

该标准将基于范围的 for 语句定义为等同于:

The standard defines the range-based for statement to be equivalent to:

{
  auto && __range = range-init;
  for ( auto __begin = begin-expr,
             __end = end-expr;
        __begin != __end;
        ++__begin ) {
    for-range-declaration = *__begin;
    statement
  }
}

在您的情况下， range-init 是(data)， begin-expr 是 __ range ， end-expr 是 __ range + 5 ， for-range-clarification 是 int元素和 statement 是 ... .也就是说，如果我们替换所有这些，则您的 for 循环等效于:

In your case, range-init is (data), begin-expr is __range, end-expr is __range + 5, for-range-declaration is int element and statement is .... That is, if we substitute all of these, your for loop is equivalent to:

{
  auto && __range = (data);
  for ( auto __begin = __range,
             __end = __range + 5;
        __begin != __end;
        ++__begin ) {
    int element = *__begin;
    ...
  }
}

此翻译是否实际上由编译器完成是实现细节.您唯一可以保证的是，您的代码将与上面的代码等效.

Whether this translation is actually done by the compiler is an implementation detail. The only thing you can guarantee is that your code will be equivalent to the above code.

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