Can someone explain why this isn't an infinite loop? (C++)

[PNGeng]

This was a question from my C++ midterm.

I see an infinite loop, but the correct answer is 12. Can anyone explain this?

Question: What is the value of i after the loop exits?
int i;
for(i=0; i < 10; i++)
i+=3;
i=1;

[DaleSwanson]

Think like a compiler; ignore white space; treat semicolons as ends of lines.

[jhae2.718]

I'm assuming that should be:

int i;
for(i=0; i < 10; i++)
i+=3;
i+=1;

as otherwise the answer would be 1.

The best way is to step through the code by hand:

Iteration Value i<10?
1 3 yes // starts at zero then adds 3
2 7 yes // incremented by 1, then add 3
3 11 no // same, then stops at next test

then add one to get 12.

[dimensionless]

The loop ends when i = 10 or i > 10. This condition is set in the line:

for(i=0; i < 10; i++)

[rcgldr]

Without any braces, the for loop only includes the next statement. The equivalent code with braces would be:


int i;

for(i=0; i < 10; i++)
{
i+=3;
}

i=1;