Is this a reasonable use of the ternary operator? [closed]

Answer 1

I think you would be better served in doing a proper if structure. I even prefer to always have braces with my if structures, in the event I have to add lines later to the conditional execution.

if (inVar != 0) {
    v.push_back(inVar);
}

Answer 2

A proper if statement is more readable, as others have mentioned. Also, when you're stepping through your code with a debugger, you won't be able to readily see which branch of an if is taken when everything is in one line or you're using a ternary expression:

if (cond) doIt();

cond ? noop() : doIt();

Whereas the following is much nicer to step through (whether you have the braces or not):

if (cond) {
    doIt();
}

Answer 3

As mentioned, it's not shorter or clearer than a 1 line if statement. However, it's also no longer - and isn't really that hard to grok. If you know the ternary operator, it's pretty obvious what's happening.

After all, I don't think anyone would have a problem if it was being assigned to a variable (even if it was mutating state as well):

var2 = inVar1 == 0 ? NULL : v.push_back(inVar1);

The fact that the ternary operator always returns a value - IMO - is irrelevant. There's certainly no requirement that you use all return values...after all, an assignment returns a value.

That being said, I'd replace it with an if statement if I ran across it with a NULL branch.

But, if it replaced a 3 line if statement:

if (inVar == 0) {
   v.doThingOne(1);
} else {
   v.doThingTwo(2);
}

with:

invar1 == 0 ? v.doThingOne(1) : v.doThingTwo(2);

I might leave it...depending on my mood. ;)

Answer 4

As litb mentioned in the comments, this isn't valid C++. GCC, for example, will emit an error on this code:

error: `(&v)->std::vector<_Tp, _Alloc>::push_back [with _Tp = int, _Alloc =
std::allocator<int>](((const int&)((const int*)(&inVar1))))' has type `void' 
and is not a throw-expression

However, that can be worked around by casting:

inVar1 == 0 ? (void)0 : v.push_back(inVar1);
inVar2 == 0 ? (void)0 : v.push_back(inVar2);

But at what cost? And for what purpose?

It's not like using the ternary operator here is any more concise than an if-statement in this situation:

inVar1 == 0 ? NULL : v.push_back(inVar1);
if(inVar1 != 0) v.push_back(inVar1);