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#43264 - 04/26/13 08:56 AM Case Statement in Design/PPTalk Please
Kap Offline
OL User

Registered: 10/20/10
Posts: 80
I think it would be really useful (and easier on the eyes) if we could have a case statement in PPTalk.

I know I can do if/ifelse statements but it takes more writing and is a harder to follow (to my eyes).

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#43270 - 04/26/13 12:40 PM Re: Case Statement in Design/PPTalk Please [Re: Kap]
Philippe F. Offline
OL Expert

Registered: 09/06/00
Posts: 1972
Loc: Objectif Lune, Montreal, Qc
Yes, but the if() ... elseif() construct is more flexible because it allows you to compare different values.

For instance, in a classic language with a CASE construct, you'd have something like this:
Code:

CASE MyVariable of
  1: @DoOneThing()
  2: @DoAnotherThing()
  3,4,5: @DoYetAnotherThing()
  else
    @DoDefault()
ENDCASE

But MyVariable can only be - in this instance - a numeric value.

With an if()...elseif() construct, you can mix and match data types:
Code:
IF((MyVariable=1) and (MyOtherBooleanVariable))
  @DoOneThing()
ELSEIF((MyVariable=2) and (MyStringVariable="INVOICE"))
  @DoAnotherThing()
ELSEIF((MyVariable>2) and (MyVariable<=5) and @MyCustomFunction())
  @DoYetAnotherThing()
ELSE
  @DoDefault
ENDIF


A case - no pun intended - could be made that the case structure is more efficient since only one of the expressions is evaluated, whereas an if()...elseif() construct evaluates all conditions until it finds the proper match, thereby resulting in better performance, but I doubt that anyone could actually measure that performance increase in a real world scenario.

It should also be stated that PlanetPress Talk is a function-based language: each statement (and indeed, each operator) is actually a function call. So if we were to implement a case statement, it would likely look like this:
Code:
switchcase(&MyVariable)
case([1], @DoOneThing())
case([2], @DoAnotherThing())
case([3,4,5], @DoYetAnotherThing())
caseelse(DoDefault)
endswitchcase

We'd have to use an array as the first parameter because PlanetPress Talk functions do not accept a variable number of parameters (well... at least not as its first arguments). Not to mention that we'd have to find a way for the function to accept arrays of different data types, something that's not natively possible for function calls in PlanetPress Talk

And in the end, if you ask me, that syntax is not much leaner than the current if()...elseif() one. Unfortunately, we're a bit limited in the types of implementations we can add to the language.
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#43337 - 05/02/13 04:57 AM Re: Case Statement in Design/PPTalk Please [Re: Kap]
Kap Offline
OL User

Registered: 10/20/10
Posts: 80
Now that I know how it works internally I'm happy to stick with if/else! Thanks for the explanation.

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