有什么区别++ i和i ++的区别 [英] What is the difference between ++i and i++

问题描述

在C，是两者的区别： ++我和我++ ，并应在使用一个为循环的增量块？

In C, what is the difference between using ++i and i++, and which should be used in the incrementation block of a for loop?

推荐答案

• ++我将递增 i的值，然后返回增加后的值。

• ++i will increment the value of i, and then return the incremented value.

   i = 1;
   j = ++i;
   (i is 2, j is 2)
  




• 我++ 将递增 i的值，但返回的原始值 I 递增之前举行。

• i++ will increment the value of i, but return the original value that i held before being incremented.

   i = 1;
   j = i++;
   (i is 2, j is 1)
  




对于为循环，无论是作品。 ++我似乎更常见，可​​能因为这是在 K＆放大器使用; - [R 。

For a for loop, either works. ++i seems more common, perhaps because that is what is used in K&R.

在任何情况下，按照指引preFER ++我在 i ++ ，你赢了T出问题。

In any case, follow the guideline "prefer ++i over i++" and you won't go wrong.

有一个关于 ++我和我++ 的效率夫妇的意见。在任何非学生项目的编译器，将不会有性能差异。您可以通过查看生成的code，这将是相同的验证。

There's a couple of comments regarding the efficiency of ++i and i++. In any non-student-project compiler, there will be no performance difference. You can verify this by looking at the generated code, which will be identical.

效率问题是有趣......这里是我的上述问题的回答：
是否有性能差异之间我++和++我用C？

The efficiency question is interesting... here's my attempt at an answer: Is there a performance difference between i++ and ++i in C?

作为的在弗氏的笔记，它是一个C ++对象不同，因为符++（）是一个函数，编译器无法知道优化掉临时对象的创建来保存中间值。

As On Freund notes, it's different for a C++ object, since operator++() is a function and the compiler can't know to optimize away the creation of a temporary object to hold the intermediate value.

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