CompilerIf doesn't do short-circuit ?

[Martt]

PB does support short-circuit (https://en.wikipedia.org/wiki/Short-circuit_evaluation). Very helpfull.

The following code in 5.71 and 5.72 does not work (constant not found: #Test):

Code: Select all

;#Test = #True

CompilerIf Defined(Test, #PB_Constant) And #Test
    Debug "Hi there"
CompilerEndIf

Is there a reason ? Solvable of course by using a nested CompilerIf...

Code: Select all

;#Test = #True

CompilerIf Defined(Test, #PB_Constant)
    CompilerIf #Test
        Debug "Hi there"
    CompilerEndIf
CompilerEndIf

[wombats]

A semicolon in PureBasic is used to denote a comment. You don't need them in front of constants. Remove it and it'll work.

[Martt]

A semicolon in PureBasic is used to denote a comment. You don't need them in front of constants. Remove it and it'll work.

Of course it works without the semicolon. The whole point is to check if a constant exists (part 1). If it doesn't exist the second part should not be checked.
That is what short-circuit is all about. Since part 1 is zero, the And cannot possibly become true. So with short-circuit the second part will never be checked.

[wombats]

Well, this does the same:

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If 1 + 1 = 3 And #Test
  Debug "Hi there"
EndIf

Maybe it's a bug?

Running the following on macOS doesn't output "Hi there":

Code: Select all

#Test = #True

CompilerIf #PB_Compiler_OS = #PB_OS_Windows And #Test
  Debug "Hi there"
CompilerEndIf

[JagV12]

@wombat : of course it doesn't output "Hi there" but that's not the point here. AFAI understand Martt's point, if the first term of an AND statement in a CompilerIf evaluates as False, the second term shouldn't raise an error at compile time because of Short-circuit_evaluation. But it does here as shown with his first example code.

@Martt : obviously no Short-circuit_evaluation at compile time. a)Did it work with older PB versions ? b)What don't you like (what is it you don't like ?) with nested CompileIf ?

[Fred]

The whole line is always parsed and expected to be syntax correct before the evaluation begins. It is to avoid spelling mistake for example (if you had used #Testt instead, it would work as well but wouldn't do what you were expecting).

[Little John]

The whole line is always parsed and expected to be syntax correct before the evaluation begins. It is to avoid spelling mistake for example (if you had used #Testt instead, it would work as well but wouldn't do what you were expecting).

Good idea, it's much appreciated.
Thanks for that!

[Martt]

@JagV12: I thought I tested this a while ago, but v5.62 also doesn't do it. Looks like it never worked that way. I allways try to use one line If's. Cleaner code.

@Fred: Thanks for the explanation.