为什么在许多C ++标准库代码中将不等式测试为(！(a == b))? [英] Why is inequality tested as (!(a==b)) in a lot of C++ standard library code?

问题描述

这是C ++标准库 remove 代码中的代码.为什么不等式被测试为 if(！(* first == val))而不是 if(* first！= val)?

This is the code from the C++ standard library remove code. Why is inequality tested as if (!(*first == val)) instead of if (*first != val)?

 template <class ForwardIterator, class T>
      ForwardIterator remove (ForwardIterator first, ForwardIterator last, const T& val)
 {
     ForwardIterator result = first;
     while (first!=last) {
         if (!(*first == val)) {
             *result = *first;
             ++result;
         }
         ++first;
     }
     return result;
 }

推荐答案

因为这意味着对T的唯一要求是实现 operator == .您可能要求T具有 operator！= ，但是这里的总体思路是，您应该给模板的用户带来尽可能少的负担，而其他模板确实需要 operator == .

Because this means the only requirement on T is to implement an operator==. You could require T to have an operator!= but the general idea here is that you should put as little burden on the user of the template as possible and other templates do need operator==.

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