“++”之间的区别是什么？和“+ = 1”运营商？ [英] What is the difference between "++" and "+= 1 " operators?

问题描述

在C ++的循环中，我通常遇到使用 ++ 或 + = 1 不能告诉他们的区别。例如，如果我有一个整数

  int num = 0; 
  

，然后在循环中执行：

  num ++; 
  

或

  num + = 1; 
  

它们都会增加 num 的值，但是他们的区别是什么？我怀疑 num ++ 可以工作得比 num + = 1 ，但如何？这个差别是否微妙到足以被忽略？

解决方案

num + = 1 所有这些表达式（ num + = 1 ，

num ++ 和 ++ num ）递增 num ，但是 num ++ 的值是 num 之前的 增加之前的值。

说明：

  int a = 0; 
 int b = a ++; // now b == 0 and a == 1 
 int c = ++ a; // now c == 2 and a == 2 
 int d =（a + = 1）; // now d == 3 and a == 3 
  

使用任何你喜欢的。我更喜欢 ++ num 到 num + = 1 ，因为它更短。

In a loop in C++, I usually encounter situations to use ++ or +=1, but I can't tell their difference. For instance, if I have an integer

int num = 0;

and then in a loop I do:

num ++;

or

num += 1;

they both increase the value of num, but what is their difference? I doubt num++ could work faster than num+=1, but how? Is this difference subtle enough to be ignored?

解决方案

num += 1 is rather equivalent to ++num.

All those expressions (num += 1, num++ and ++num) increment the value of num by one, but the value of num++ is the value num had before it got incremented.

Illustration:

int a = 0;
int b = a++; // now b == 0 and a == 1
int c = ++a; // now c == 2 and a == 2
int d = (a += 1); // now d == 3 and a == 3

Use whatever pleases you. I prefer ++num to num += 1 because it is shorter.

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