what does "a

Question

I saw this code

a<?=b; // (a and b are int)

from the solution of Google Code Jam.

but my VS shows an error on '?'

I only know the following:

a>b?a=0:b=0;

Thanks.

https://code.google.com/codejam/contest/32003/scoreboard?c=32003#vf=1 Please check sclo's answer for problem c 40pt. — czhao86, Feb 24 '14 at 20:52

score 9 · Answer 1 · answered Feb 24 '14 at 20:51

9

Old operator; it's a (since removed) gcc extension for 'minimum'. That is:

a <?= b;

is the same as:

a = a < b ? a : b;

answered Feb 24 '14 at 20:51

Carl Norum

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1

Wow, I was sure that was not valid – jeremy Feb 24 '14 at 20:51
1

I guess its not C/c++ valid, but it is gcc valid (or was gcc valid :) ) – jeremy Feb 24 '14 at 20:52
@jeremy the question is about c++ – David Heffernan Feb 24 '14 at 20:53
@jeremy: as the OP discovered, compiler extensions may not be valid on other compilers. (A pretty cool operator nevertheless. I'm *sure* I could have used it here or there.) – Jongware Feb 24 '14 at 20:53
For those interested in more: http://gcc.gnu.org/onlinedocs/gcc/Deprecated-Features.html – AndyG Feb 24 '14 at 20:54
Even `--std=gnu++98` doesn't re-enable that extension. – Jason C Feb 24 '14 at 20:55

score 1 · Answer 2 · answered Feb 24 '14 at 20:51

A nonstandard GCC extension to C++ allows <? as an operator which is equivalent to min. I haven't seen <?= before, but presumably it's an in-place version; that is, a <?= b is equivalent to a = min(a,b).

Note that the GCC developers woke up the next morning and realized what a bad idea that was. The operator is now deprecated.

score 1 · Answer 3 · answered Feb 24 '14 at 20:52

If a happens to be larger than b, it would set a to b.

Essentially the same as:

a = a < b ? a : b;

Example:

int a = 5;
int b = 2;
a<?=b; //a is now 2!

I wouldn't advocate actually using such a solution though, it is horrible.

As others have said, it's part of a nonstandard GCC extension, but please don't use it.

what does "a

3 Answers3