I am curious if there is any difference between assigning the output of a function foo() to a variable and then prefixing the logical negation ! operator vs. prefixing the logical negation operator directly before the function. i.e. is
int output = foo();
if(!output){
}
formally equivalent to:
if(!foo()) {
}
This probably isn't what you're thinking of, but it is a difference between your two example code fragments, and an important one: in
int output = foo();
if (!output) {
...
}
...
the variable output, and therefore the value returned from the function, is available to code both inside and below the if-statement. In your other example, the value returned from the function is not available to anything but the ! operator inside the if-condition.
This is probably the most important practical reason to choose one form or the other; do you need that value for anything besides the if-condition? If so, you need the variable.