Author Topic: is there a way to get the name of a function to call from a variable or data? (Read 5265 times)

madscijr · « **on:** January 26, 2022, 03:40:38 am »

In VBA, you can do something like

Code: Text: [Select]

sFunctionName = "MyFunction"
sParameter1 = "MyValue"
If Len(Trim(sFunctionName)) > 0 Then
        If Len(sParameter1) = 0 Then
                Application.Run sFunctionName
        Else
                Application.Run sFunctionName, sParameter1
        End If
End If
 

Is there any way to do this kind of thing in QB64?

I know that using eval and running code from data isn't the most "secure" practice, and for anything public-facing I would avoid it,
but it can come in handy for testing a large number of functions or quickly (re)defining a menu in data when prototyping a design, etc.

luke · « **Reply #1 on:** January 26, 2022, 07:50:46 am »

In a word, no. VBA can easily do this by virtue of being an interpreted language; QB64 is always compiled which makes such things much harder (I'm sure someone will come up with a hack using DECLARE LIBRARY to prove me wrong).

RhoSigma · « **Reply #2 on:** January 26, 2022, 09:13:47 am »

Hi @madscijr,

a while back I made some experiments, but only with parameterless functions. You need to know the names of your SUBs/FUNCs at the C side of things (usually the all uppercase name + SUB_/FUNC_ prefix) and define helper functions to take their address (_OFFSET), over which you can later call it.

save as hookfunc.h

Code: C: [Select]

// stubs to get the addresses of the defined QB64 SUBs/FUNCs
// there must be an entry for each SUB/FUNC you need
int16 FUNC_TEST(); ptrszint GetHook_Test(void) {return (ptrszint)&FUNC_TEST;}
int16 FUNC_TEST2(); ptrszint GetHook_Test2(void) {return (ptrszint)&FUNC_TEST2;}
 
// call the function via its address, which on QB64 side may be stored
// in a _OFFSET variable, if you need other return types, then you may
// copy this typdef & function with slighly different names and redefine
// the int16 type as needed, however no tests yet how to pass arguments
typedef int16 (*fp)();
int16 CallHook(ptrszint hook) {
    fp func = (fp)hook;
    return func();
}
 
 

save as hookfunc.bas

Code: QB64: [Select]

'the functions in hookfunc.h
DECLARE LIBRARY "hookfunc" 'no .h here !!
    FUNCTION GetHook_Test%& ()
    FUNCTION GetHook_Test2%& ()
    FUNCTION CallHook% (BYVAL hook%&)
END DECLARE
 
'get/print address of FUNCTION Test%
h%& = GetHook_Test%&
PRINT h%&
'call FUNCTION Test% via its address
PRINT CallHook%(h%&)
 
PRINT
 
'get/print address of FUNCTION Tes2%
h%& = GetHook_Test2%&
PRINT h%&
'call FUNCTION Test2% via its address
PRINT CallHook%(h%&)
 
'that all folks
END
 
FUNCTION Test% ()
PRINT "This is function Test%()"
Test% = 0
END FUNCTION
 
FUNCTION Test2% ()
PRINT "This is function Test2%()"
Test2% = -1
END FUNCTION
 
 

madscijr · « **Reply #3 on:** January 26, 2022, 09:26:06 am »

Quote from: luke on January 26, 2022, 07:50:46 am

In a word, no. VBA can easily do this by virtue of being an interpreted language; QB64 is always compiled which makes such things much harder (I'm sure someone will come up with a hack using DECLARE LIBRARY to prove me wrong).

That's about what I expected - thanks for the swift response! It's not a feature I will die without, so no worries, I just figured it can't hurt to ask.

madscijr · « **Reply #4 on:** January 26, 2022, 09:28:00 am »

Quote from: RhoSigma on January 26, 2022, 09:13:47 am

a while back I made some experiments, but only with parameterless functions. You need to know the names of your SUBs/FUNCs at the C side of things (usually the all uppercase name + SUB_/FUNC_ prefix) and define helper functions to take their address (_OFFSET), over which you can later call it.

Wow, interesting. This should be fun to play with. You are truly a wizard! Thanks for sharing that workaround!

SpriggsySpriggs · « **Reply #5 on:** January 26, 2022, 11:54:09 am »

There's another way of doing this that's slightly more intuitive. I'll see if I can find my code for it

madscijr · « **Reply #6 on:** January 26, 2022, 03:46:42 pm »

Quote from: SpriggsySpriggs on January 26, 2022, 11:54:09 am

There's another way of doing this that's slightly more intuitive. I'll see if I can find my code for it

Sure, I would love to see what can be done.

bplus · « **Reply #7 on:** January 26, 2022, 03:47:53 pm »

You could read the source file and make a list of functions used, pretty easy.

You could dim shared a variable string, Iam$ and label all your functions with Iam$ = function name then just print the function name when ever needed.

Another: You could make a menu and call what ever function you want to check

Solutions that don't need anything special.

madscijr · « **Reply #8 on:** January 27, 2022, 12:26:29 am »

Quote from: bplus on January 26, 2022, 03:47:53 pm

Solutions that don't need anything special.

That's what I ended up doing - you'll see when I post the next program (a collection of audio examples).

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Author Topic: is there a way to get the name of a function to call from a variable or data? (Read 5265 times)

madscijr

is there a way to get the name of a function to call from a variable or data?

luke

Re: is there a way to get the name of a function to call from a variable or data?

RhoSigma

Re: is there a way to get the name of a function to call from a variable or data?

madscijr

Re: is there a way to get the name of a function to call from a variable or data?

madscijr

Re: is there a way to get the name of a function to call from a variable or data?

SpriggsySpriggs

Re: is there a way to get the name of a function to call from a variable or data?

madscijr

Re: is there a way to get the name of a function to call from a variable or data?

bplus

Re: is there a way to get the name of a function to call from a variable or data?

madscijr

Re: is there a way to get the name of a function to call from a variable or data?