Allow Recursive Macros

[GedB]

PB4 is does a great job of detecting and rejecting recursive macros.

This is great protection of the programmer who only wants nice simple macros.

However, for those of us who like to do all kinds of perverse things with Macros its a little frustrating.

Could something be added to override the recursion checking, so that those of us who want to get all LISPish can?

[Dare2]

How do you get recursion in a macro without it going infinite?

Not knocking your request, btw! I am genuinely curious - would love to see an example of what you mean, and learn from it.

[GedB]

Dare2,

I'd like to try something like this:

Code: Select all

Macro RecursiveCountDownToZero(i)
  CompilerIf i > 0
    RecursiveCountDownToZero(i - 1)
  CompilerEndIf
EndMacro

[freak]

The CompilerIF is only processed once the macro is fully expanded, so you get an infinite recursion here.

[Lebostein]

Yes, I had a similar problem with CompilerIf and macros:

Code: Select all

Macro FunctionCall
  CompilerIf #PB_Compiler_OS = #PB_OS_Windows
    CallFunction
  CompilerElse
    CallCFunction
  CompilerEndIf
EndMacro

FunctionCall(1, "test")

The solution is to create two macros:

Code: Select all

CompilerIf #PB_Compiler_OS = #PB_OS_Windows
  Macro FunctionCall
    CallFunction
  EndMacro
CompilerElse
  Macro FunctionCall
    CallCFunction
  EndMacro
CompilerEndIf

FunctionCall(1, "test")

Edit: oh, it's a other topic, sorry...

[GedB]

Hmmm, I see.

If only it could be worked out to allow this style of programming, then Macros could become so powerful.

[Fred]

The problem is it would also be much more slower..

[helpy]

Code: Select all

Macro RecursiveCountDownToZero(i)
  CompilerIf i > 0
    RecursiveCountDownToZero(i - 1)
  CompilerEndIf
EndMacro

There is another problem:
Variables are not allowed in CompilerIf statement. Variables are calculated at runtime ... CompilerIf statements are parsed at compile time.

[freak]

Just pass a constant for i, where is the problem ?

[helpy]

Just pass a constant for i, where is the problem ?

i was just thinking "one way" ... because the possibility to pass a variable is there.

And the "i" in the recursive macro is just working like an variable.

I assume that the replacement of all macros is just done right before compile time. So it is not possible to combine the functionality of Macros and CompileIf.

In order to get recursive macros working, there should have to be new macro-keywords ... something like MacroIf, MacroEndIf, MacroElse ...

cu,