以下C代码转换为什么？

Question

So I have a for loop which goes like this:

for(span=N>>1;span;span>>=1)

I am assuming the start and end conditions are equivalent to as follows:

span = N>>1; //right shift N by 1 and initialize to span
while(span!=0)
{
 span = span >> 1;
}

However it seems a little bizarre in the context of my code. Thanks in advance!

Answer 1

In every iteration you are dividing the variable span by 2 until it reaches 0.

so if initially N = 8, then values for span will be 4, 2, 1, 0 -> exit loop

Answer 2

That is correct.

• The initializer sets span = N >> 1 , right-shifting N by 1.
• The loop condition is span , which is equivalent to span != 0 .
• Every time the loop comes around, span is right-shifted again by 1.

In the context of positive integers, this is equivalent to for(span=N/2;span>0;span/=2) . However, without knowing your particular context I cannot comment whether this is or is not bizarre.

Answer 3

简短而甜美...是的，只要您已经展示了代码，您的解释就坚定而良好。