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

[madscijr]

In VBA, you can do something like

Code: Text: [Select]

1. sFunctionName = "MyFunction"
2. sParameter1 = "MyValue"
3. If Len(Trim(sFunctionName)) > 0 Then
4.         If Len(sParameter1) = 0 Then
5.                 Application.Run sFunctionName
6.         Else
7.                 Application.Run sFunctionName, sParameter1
8.         End If
9. End If
10.  

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]

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]

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]

1. // stubs to get the addresses of the defined QB64 SUBs/FUNCs
2. // there must be an entry for each SUB/FUNC you need
3. int16 FUNC_TEST(); ptrszint GetHook_Test(void) {return (ptrszint)&FUNC_TEST;}
4. int16 FUNC_TEST2(); ptrszint GetHook_Test2(void) {return (ptrszint)&FUNC_TEST2;}
5.  
6. // call the function via its address, which on QB64 side may be stored
7. // in a _OFFSET variable, if you need other return types, then you may
8. // copy this typdef & function with slighly different names and redefine
9. // the int16 type as needed, however no tests yet how to pass arguments
10. typedef int16 (*fp)();
11. int16 CallHook(ptrszint hook) {
12.     fp func = (fp)hook;
13.     return func();
14. }
15.  
16.  

save as hookfunc.bas

Code: QB64: [Select]

1. 'the functions in hookfunc.h
2. DECLARE LIBRARY "hookfunc" 'no .h here !!
3.     FUNCTION GetHook_Test%& ()
4.     FUNCTION GetHook_Test2%& ()
5.     FUNCTION CallHook% (BYVAL hook%&)
6. END DECLARE
7.  
8. 'get/print address of FUNCTION Test%
9. h%& = GetHook_Test%&
10. PRINT h%&
11. 'call FUNCTION Test% via its address
12. PRINT CallHook%(h%&)
13.  
14. PRINT
15.  
16. 'get/print address of FUNCTION Tes2%
17. h%& = GetHook_Test2%&
18. PRINT h%&
19. 'call FUNCTION Test2% via its address
20. PRINT CallHook%(h%&)
21.  
22. 'that all folks
23. END
24.  
25. FUNCTION Test% ()
26. PRINT "This is function Test%()"
27. Test% = 0
28. END FUNCTION
29.  
30. FUNCTION Test2% ()
31. PRINT "This is function Test2%()"
32. Test2% = -1
33. END FUNCTION
34.  
35.  

[madscijr]

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]

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]

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

[madscijr]

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]

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]

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).