What is the meaning of this syntax, relating to c++

Question

return int_length(len > 0 ? len : 1)

what is the meaning of the syntax in the brackets, I keep getting confused when reading this code. thanks

Ternary operator: [ternary wiki](http://en.wikipedia.org/wiki/%3F:) - a very condensed if-else. — wkl, Jun 21 '13 at 14:18
@Daniel, apparently somebody's thinking that answering a duplicate deserves downvotes. (Hint: it usually does not.) — Frédéric Hamidi, Jun 21 '13 at 14:20
Off-topic: It's interesting how _I_ got notified of the previous comment by Frédéric Hamidi. @DanielA.White, where you notified, too? — Daniel Daranas, Jun 21 '13 at 14:21
Everything was being downvoted that was correct.... strange. — Tyler Jandreau, Jun 21 '13 at 14:21
I'm not the downvoter, but the correct term is "conditional operator". See http://stackoverflow.com/questions/3257229/what-are-these-called#comment3367165_3257229 :) — Daniel Daranas, Jun 21 '13 at 14:22
It's also damned silliness here. Why not `return int_length(max(len, 1))`? Yes, I know a `using` statement is needed for that. But wouldn't that be clearer? — Eric Jablow, Jun 21 '13 at 14:23

score 4 · Answer 1 · answered Jun 21 '13 at 14:18

4

It is a ternary operator. If len>0 is true result of the expression is len else its 1.

if(len > 0) it will return int_length(len);

else it will return int_length(1);

answered Jun 21 '13 at 14:18

Vivek Sadh

score 3 · Answer 2 · answered Jun 21 '13 at 14:18

3

That's the ternary operator.

It's equivalent to

if (len>0)
    return int_length(len);
else
    return int_length(1);

answered Jun 21 '13 at 14:18

Luchian Grigore

Why the -1 on this? Upvoting. – Captain Skyhawk Jun 21 '13 at 14:20
why -1 on all correct answers? wtf.. – Yami Jun 21 '13 at 14:20
1

Because they're not strictly speaking correct. In this case, the answer gives something equivalent to the complete statement; the poster asked about the actual expression that was an argument to `int_length`. (Not that I think that's an valid reason to downvote, but it's the only criticism I can think of.) – James Kanze Jun 21 '13 at 14:26

score 2 · Answer 3 · edited Jun 21 '13 at 14:20

2

it means

if(len > 0)
{
   return int_length(len);
}
else
{  
   return int_length(1);
}

edited Jun 21 '13 at 14:20

Matteo Italia

answered Jun 21 '13 at 14:19

Yami

1

Except that it's an order of magnitude more readable. – James Kanze Jun 21 '13 at 14:24

score 1 · Answer 4 · answered Jun 21 '13 at 14:18

1

That is the ternary conditional operator. Its an "inline if".

It basically is this

int temp;
if (len > 0)
{
  temp = len;
}
else
{
  temp = 1;
}

int_length(temp);

answered Jun 21 '13 at 14:18

Daniel A. White

4 Answers4