有什么区别++ i和i ++的区别

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。

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：


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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