初学者C“ ==”始终计算为false

Question

Just a beginner question. I tried to find an answer to this but I couldn't.

Why

for (int i = 0;i==10;++i) {
/* body of the for loop */
}

Never executes the body of the for loop? but this one works?

for (int i = 0;i<=10;++i) {
/* body of the for loop */
}

The (i==0) should be a boolean expression evaluating to false if i==0, right? This perfectly works if I put that expression in an if statement like

for(int i=10;;++i) {
if (i==10) break;
}

Thanks!

Answer 1

C ++ 101：中间条件必须为true，循环才能继续。

Answer 2

A for loop basically means to continue as long as the middle condition is true.

So the loop, in this case will only continue when i==10. Which it isn't therefore it stops.

Answer 3

Because the condition in your first loop says only to increment when i is equal to to 10. You set i to 0, so it will never increment because it has no way of getting there.

The second one works because you say i is equal to 0, and while i is less than or equal to 10, it is incremented by 1. 0 is less than 10, but not equal to it.

Answer 4

for (int i = 0; <condition>;++i) {
/* body of the for loop */
}

The key to understanding this is that the body executes every time the condition evaluates to TRUE. In your example, it evaluates to FALSE first time itself, and hence nothing executes.

In your second example, condition is omitted. Which means the body executes forever, until you break out of it. Which you do when i == 10. Hence the body executes 10 times.

Answer 5

for(;true;)
{
//this is infinite loop
}

为了进入循环，条件应该为true，在您的情况下，i == 10返回false，因此不会进入循环。

Answer 6

        for (int i = 0;i==10;++i) {
         /* body of the for loop */
        }

for this code i=0 initially, when condition is checked (i==10) it results in false so loop will not iterate.

Check carefully for what values of i you want to run the loop.

for example your loop may be

     for (int i = 0;i<=10;++i) {
       /* body of the for loop */
      }

the body of loop will iterate from 0 to 10 including both.