在if语句中首先放置常量的原因是什么？ [英] What's the reasoning behind putting constants in if statements first?

问题描述

我在看一些例子C ++代码的硬件接口我正在使用，并注意到许多语句沿以下行：

I was looking at some example C++ code for a hardware interface I'm working with and noticed a lot of statements along the following lines:

if ( NULL == pMsg ) return rv;

我相信我听说有人说把恒定放在第一位是个好主意，这是为什么？只是这样，如果你有一个大的声明，你可以很快看到你正在比较或有更多的它吗？

I'm sure I've heard people say that putting the constant first is a good idea, but why is that? Is it just so that if you have a large statement you can quickly see what you're comparing against or is there more to it?

推荐答案

因此，你不要将比较（==）与赋值（=）混合。

So that you don't mix comparison (==) with assignment (=).

如你所知，你不能分配一个常量。如果你尝试，编译器会给你一个错误。

As you know, you can't assign to a constant. If you try, the compliler will give you an error.

基本上，它是防御性编程技术之一。保护自己免受伤害。

Basically, it's one of defensive programming techniques. To protect yourself from yourself.

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