For as long as I can remember I have avoided using switch statement fall-through. Actually, I can't remember it ever entering my consciousness as a possible way to do things as it was drilled into my head early on that it was nothing more than a bug in the switch statement. However, today I ran across some code that uses it by design, which got me immediately wondering what everyone in the community thinks about switch statement fall-through.
Is it something that a programming language should explicitly not allow (like C# does, though it supplies a workaround) or is it a feature of any language that is powerful enough to leave in the programmer's hands?
Edit: I wasn't specific enough to what I meant by fall-through. I use this type a lot:
switch(m_loadAnimSubCt){
case 0:
case 1:
// Do something
break;
case 2:
case 3:
case 4:
// Do something
break;
}
However, I'm concerned about something like this.
switch(m_loadAnimSubCt){
case 0:
case 1:
// Do something, but fall through to the other cases
// after doing it.
case 2:
case 3:
case 4:
// Do something else.
break;
}
This way whenever the case is 0, 1 it will do everything in the switch statement. I've seen this by design and I just don't know if I agree that switch statements should be used this way. I think the first code example is very useful and safe. The second seems kind of dangerous.
It may depend on what you consider fallthrough. I'm ok with this sort of thing:
switch (value)
{
case 0:
result = ZERO_DIGIT;
break;
case 1:
case 3:
case 5:
case 7:
case 9:
result = ODD_DIGIT;
break;
case 2:
case 4:
case 6:
case 8:
result = EVEN_DIGIT;
break;
}
But if you have a case label followed by code that falls through to another case label, I'd pretty much always consider that evil. Perhaps moving the common code to a function and calling from both places would be a better idea.