Is it necessary to write else part in every if condition?

Question

The question I asked might be closed, But i just want to know that is it necessary to write else part of every if condition. One of my senior programmer said me that \"you shoul

Answer 1

Looking at this purely from a semantic point of view - I cannot think of a single case where there is not an implicit else for every if.

if the car is not stopped before I reach the wall I will crash, else I will not crash.

Semantics aside:

The answer to that question depends on the environment, and what the result of a mistake is.

Business code? Do what your coding standards say.
IMHO you will find that spelling it out, although initially it seems like too much work, will become invaluable 10 years from now when you revisit that code. But, it certainly would not be the end of the world if you missed an important 'anti-condition'.

However: Security, Safety or Life Critical code? That's a different story.

In this case you want to do two things.
First:Rather than testing for a fault, you want to prove there is not a fault. This requires a pessimistic view on entry to any module. You assume everything is wrong until you prove it is correct.
Second: in life critical: You NEVER want to hurt a patient.:

bool everyThingIsSafe = true;
if(darnThereIsAProblem())
{
   reportToUserEndOfWorld();
}
return everyThingIsSafe;

Oops. I forgot to set everyThingIsSafe false.
The routine that called this snippit is now lied to. Had I initialized evertThingIsSafe to false - I'm always safe, but now I need the else clause to indicate that there wasn't an error.
And yes, I could have changed this to a positive test - but then I need the else to handle the fault.
And yes, I could have assigned everyThingIsSafe() the immediate return of the check. And then tested the flag to report a problem. An implicit else, why not be explicit?
Strictly speaking, the implicit else this represents is reasonable.
To an FDA/safety auditor, maybe not.
If it's explicit, can point to the test, its else, and that I handled both conditions clearly.

I've been coding for medical devices for 25 years. In this case, you want the else, you want the default in the case, and they are never empty. You want to know exactly what is going to happen, or as near as you can. Because overlooking a condition could kill someone.

Look up Therac-25. 8 severely injured. 3 dead.