具有空第二个参数的C条件运算符('?') [英] C conditional operator ('?') with empty second parameter

问题描述

通常是?"运算符以以下形式使用:

Typically the '?' operator is used in the following form:

A ? B : C

但是在B = A的情况下，我看到以下缩写

However in cases where B = A I have seen the following abbreviation

A ? : C

这出奇地有效.最好将第二个参数保留为(样式明智的)，还是某些编译器将无法处理此参数?

This surprisingly works. Is it better to leave the second parameter in (style wise), or is their a chance certain compilers won't be able to handle this?

推荐答案

C语言不允许(据我所知)，但是gcc之类的编译器将快捷方式a?:c用作扩展名. a?:c 的含义与 a?a:c 相同.

It is not permitted by the language C (as far as I know), but compilers such as gcc have the shortcut a?:c as an extension. a?:c means the same as a?a:c.

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