循环中的前增量和后增量之间的区别? [英] Difference between pre-increment and post-increment in a loop?

问题描述

for循环中的++i和i++是否存在差异?仅仅是语法吗?

Is there a difference in ++i and i++ in a for loop? Is it simply a syntax thing?

推荐答案

a ++被称为后缀.

向a加1，返回旧值.

++ a被称为前缀.

向a加1，返回新值.

C#:

string[] items = {"a","b","c","d"};
int i = 0;
foreach (string item in items)
{
    Console.WriteLine(++i);
}
Console.WriteLine("");

i = 0;
foreach (string item in items)
{
    Console.WriteLine(i++);
}

输出:

1
2
3
4

0
1
2
3

foreach和while循环取决于您使用哪种增量类型.像下面这样的for循环，因为您没有使用i的返回值，所以没有区别:

foreach and while loops depend on which increment type you use. With for loops like below it makes no difference as you're not using the return value of i:

for (int i = 0; i < 5; i++) { Console.Write(i);}
Console.WriteLine("");
for (int i = 0; i < 5; ++i) { Console.Write(i); }

0 1 2 3 4
0 1 2 3 4

0 1 2 3 4
0 1 2 3 4

如果使用评估值，则增量类型将变得很重要:

If the value as evaluated is used then the type of increment becomes significant:

int n = 0;
for (int i = 0; n < 5; n = i++) { }

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