+ = C ++中的运算符 [英] += Operator in C++

问题描述

有人请告诉我下面的代码添加两个变量的数据类型 int 之间的区别。我想知道哪一个更好。

Someone please tell me the difference between the following codes which add two variables of datatype int. I want to know which one is better.

代码A：

sum = sum + value;

代码B ：

sum += value;

我们通常喜欢 ++ code> + = 1 。还有什么特别的原因吗？

We usually prefer ++ operator over += 1. Is there any specific reason behind that as well ?

我想知道上述代码之间的区别，相对于约定或效率水平。

推荐答案

someVar ++ 运算符与 someVar + = 1 相同，还有其他东西。

While the end result of the e.g. someVar++ operator is the same as someVar += 1 there are other things playing in as well.

我们使用一个简单的语句，例如

Lets take a simple statement like

foo = bar++;

它实际上等同于（但不等于）

It's actually equivalent (but not equal) to

temp = bar;
bar += 1;
foo = temp;

对于前缀和后缀递增或递减运算符，它们有不同的 运算符优先级 ，这将影响像指针运算

As for the prefix and suffix increment or decrement operators, they have different operator precedence, which will affect things like pointer arithmetic using those operators.

foo += 1;

和

foo = foo + 1;

对于基本类型没有什么不同（例如 int 或 float ）或指针类型，但是如果 foo 是一个操作符重载的对象，会有很大的区别。

there's no different for primitive types (like int or float) or pointer types, but there's a very big difference if foo is an object with operator overloading. Then

foo += 1;

等于

foo.operator+=(1);

while

foo = foo + 1;

等于

temp = foo.operator+(1);
foo.operator=(temp);

语义上有很大的区别。实际上，特别是如果任何操作符重载函数有副作用，或者复制构造函数或析构函数有一些副作用（或者你忘记了三，五或零的规则）。

Semantically a very big difference. Practically too, especially if any of the operator overload functions have side-effects, or if the copy-constructor or destructor have some side-effects (or you forget the rules of three, five or zero).

这篇关于+ = C ++中的运算符的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！