If statements vs case

[Richard Gaskin]

Hershel Fisch wrote:
> Hi every one, how would one put the differences between multiple if, else
> if's vs. case's

In many respects they're quite similar, and for many uses the choice of 
one over another can be a matter of stylistic preference.

But there is at least one functional difference which may be worth 
keeping in mind; I don't use it often, but I'm grateful for it when I do:

Case statements allow a fall-through option, so that each case need not 
be exclusive the way if-then is.

For example, in this block:

switch tVar
   case "a"
   case "b"
     DoThing1
     break
   case "c"
     DoThing2
   case "d"
     DoThing3
     break
   case "e"
     DoThing4
end switch

..the cases "a" and "b" both trigger "DoThing1", and the hit the break 
so they exit.

But "c" and "d" both trigger "DoThing3", with "c" first triggering 
"DoThing2" before falling through to the next case.  It falls through 
because there is no "break" statement".   And because there is a "break" 
after "DoThing3", neither "c" nor "d" every triggers "DoThing4", since 
the "break" prevents the fall-through.

With the multiple criteria exemplified by "a" and "b" above, and the 
fall-through of having no break between "c" and "d", you can see that 
case blocks offer a level of flexibility not found in if-thens.

And for many uses, FWIW I often find case blocks easier to read.

-- 
  Richard Gaskin
  Managing Editor, revJournal
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