CODEWITHSUNDEEP
c
Pedro Kali
Pedro Kali

Reputation: 55

Understanding the enhanced syntax of for loop

I found the following for loop that I cannot understand why it looks different than the traditional one, i.e. (init; condition; increment):

int parent, i, indx;
for (; indx; indx = parent) {
    parent = (indx - 1) / 2;
    if (h->queue[parent] >= value) break;
    h->queue[indx] = h->queue[parent];
}

Can someone explain how to convert it to be in the form of (init; condition; increment)?

Upvotes: 0

Views: 56

Answers (2)

Phil
Phil

Reputation: 1256

for (; indx; indx = parent)

is the standard C for-loop. It simply has a blank (no instructions) for the initialization option.

Upvotes: 1

templatetypedef
templatetypedef

Reputation: 372992

In a for loop, each of the initialization, termination, and step expressions can be omitted. If the initialization step is skipped, there's no initialization done. If the step is skipped, no step is performed. If the test is skipped, the loop runs until it's broken out of.

Rather than trying to rewrite this loop to include all three expressions, I'd recommend investing the time to learn this syntax, since statements like these aren't all that uncommon.

Upvotes: 2

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