问题描述
说，我想用为循环用C打印消息五次。为什么，如果我后添加一个分号for循环是这样的：
Say I want to print a message in C five times using a for loop. Why is it that if I add a semicolon after for loop like this:
for (i=0;i<5;i++);
该消息不打印5次，但如果我不把分号那里呢？
the message does not get printed 5 times, but it does if I do not put the semicolon there?
推荐答案
分号是所谓合法声明的空语句的，表示什么都不做。因为为循环执行一个单一的操作（这可能是块放在 {} ）分号被视为循环体，导致在你所观察到的行为。
Semicolon is a legitimate statement called null statement that means "do nothing". Since the for loop executes a single operation (which could be a block enclosed in {}) semicolon is treated as the body of the loop, resulting in the behavior that you observed.
以下code
for (i=0;i<5;i++);
{
printf("hello\n");
}
是国际preTED如下：
is interpreted as follows:
- 重复五次
为（i = 0;我小于5;我++） - ...什么都不做（分号）
- 打开局部变量新的作用域
{ - ...打印你好
- 关闭范围
}
- Repeat five times
for (i=0;i<5;i++) - ... do nothing (semicolon)
- Open a new scope for local variables
{ - ... Print "hello"
- Close the scope
}
正如你所看到的，是被重复操作; ，而不是的printf 。
请参见，第1.5.2节
As you can see, the operation that gets repeated is ;, not the printf.
See K&R, section 1.5.2
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