In C (and C++) is it considered bad form to use comparison operators outside of conditionals?

Question

For example

int f(int a) {
   ...
   return a > 10;
}

is that considered acceptable (not legal, I mean is it ``good code''), or should it always be in a conditional, like this

int f(int a) {
   ...
   if (a > 10)
      return 1;
   else
      return 0;
}

Answer 1

This is absolutely acceptable! In fact, Joel mentioned this on the latest stackoverflow podcast. He said it was the one thing he's had to show almost every programmer that starts at Fog Creek.

Answer 2

I don't see anything wrong with it. If anything it's more concise and I think most developers with moderate experience would prefer it.

Answer 3

The first is much preferable to me, since it is more concise. (And it avoids multiple returns:)

Answer 4

I'll typically do the former over the latter.

Answer 5

I think its perfectly acceptable, provided that you ensure that you make an extra effort to maintain readability. Like I would make sure that the method name is very unambiguous and you use good variable names.

The second alternative that you provided I think is almost worse because it involves a branch statement and multiple return statements and these things increase the complexity of the method while themselves reducing its readability.

Answer 6

It would be acceptable - if your return type was bool.

Answer 7

I'd rather write bool f(int); and the first form as bool is the boolean type in C++. If I really need to return an int, I'd write something like

int f(int) {
    ...
    const int res = (i>42) ? 1 : 0;
    return res;
}

I'd never understood why people write

if (expr == true)
    mybool = true ; 
else 
    mybool = false;

instead of the plain

mybool = expr;

Boolean algebra is a tool that any developer should be able to handle instinctively

Moreover, I'd rather define a named temporary as some debuggers don't handle function return values very well.

Answer 8

The first case is perfectly good, far better than the second, IMHO. As a matter of readability, I personally would do

   return  (a > 10);

but that is a minor nit, and not one everyone would agree on.

Answer 9

return a > 10 ? 1 : 0;

... makes more sense because you're returning an int, not a bool.

Answer 10

Not only is that syntax 100% acceptable, you should also feel free to use boolean expressions outside of if statements, i.e. int x = i && ( j || k ); (or returning values like that).

Answer 11

I think part of it has to do with the style and culture of the language. The first example you have written is what would be expected from an experienced C programmer. They would much rather strangle themselves than put in an unnecessary block of statements.

I think it is perfectly acceptable when the language allows it and the usage is part of the paradigm of that language

Answer 12

I just tried three different variants with GCC:

int one(int x) { return (x > 42) ? 1 : 0; }
int two(int x) { return x > 42; }
int thr(int x) { if (x > 42) return 1; else return 0; }

As soon as you enable some optimization, the generated code for all of them is the same. So you should use the variant that is easiest to read.