0

Is it guaranteed in C that 1/2 == 0? I need that for an implementation of binary search:

/*
 * len is the array length
 * ary is an array of ptrs
 * f is a compare function
 * found is a ptr to the found element in the array
 * both i and offset are unsigned integers, used as indexes
 */

for(i = len/2; !found && i < len; i += offset) {
    res = f(c->ary[i]);

    if (res == 0) {
        found = c->ary[i];
    }
    else {
        offset = (res < 0 ? -1 : 1) * (i/2);
        if (!offset) {
            i = len+1;
        }
    }
}
templatetypedef
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musicmatze
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1 Answers1

10

Yes, this is guaranteed. According to the C ISO spec, §6.5.5/5:

The result of the / operator is the quotient from the division of the first operand by the second;

The quotient of 1 / 2 is 0, so 1 / 2 == 0 is guaranteed to be true in C.

Hope this helps!

templatetypedef
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    I'd suggest you refrain from answering obvious duplicates in the future... –  Oct 25 '13 at 20:12
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    @H2CO3- I'm sorry... I didn't realize this was a duplicate. I actually thought it was really interesting because in every C implementation I've ever seen I know that division is integer division, but I didn't know whether the C spec guaranteed this. I hoped that this answer would provide an authoritative reference beyond "it works on every compiler I've ever tried it on." – templatetypedef Oct 25 '13 at 20:26
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    Fair point. The standard guarantees this, but beware: such simple questions are *generally* already asked and answered, even multiple times. –  Oct 25 '13 at 20:27