When trying to associate an Icallback function to a button in the IUP GUI
API using the IupSetCallback function, the D compiler seems to insist on evaluating that callback in order to pass its value rather than passing the function itself.

I get this dmd compiler error (the source is named hitmeiup.d) :

Error: function hitmeiup.hitMeAct (Ihandle_* dmy) is not callable using argument types ()
hitmeiup.d(41): Error: expected 1 function arguments, not 0

for this line calling the IupSetCallback:

	IupSetCallback(btn,"ACTION",hitMeAct);

The callback function was named hitMeAct as follows:

extern(C) {
	int hitMeAct(Ihandle *dmy) {
		sayHit();
		return 0;
	}
}

I have also tried it with hitMeAct being a D function instead of extern(C).

It is as if the	call to IupSetCallback is interpreting hitMeAct to be a property function and that the call was meant to be:

	IupSetCallback(btn,"ACTION",hitMeAct());

It there someway to force D to consider the hitMeAct parameter to be passing a function and NOT calling it?  I tried prefixing a & - no go.

Would welcome any hints.

Yes I have already looked at the .d files purporting to provide access to IUP.
And a more or less equivalent C program works fine.

On Wednesday, 19 March 2014 at 02:21:18 UTC, James Wirth wrote:
> When trying to associate an Icallback function to a button in the IUP GUI
> API using the IupSetCallback function, the D compiler seems to insist on evaluating that callback in order to pass its value rather than passing the function itself.
>
> I get this dmd compiler error (the source is named hitmeiup.d) :
>
> Error: function hitmeiup.hitMeAct (Ihandle_* dmy) is not callable using argument types ()
> hitmeiup.d(41): Error: expected 1 function arguments, not 0
>
> for this line calling the IupSetCallback:
>
> 	IupSetCallback(btn,"ACTION",hitMeAct);
>
> The callback function was named hitMeAct as follows:
>
> extern(C) {
> 	int hitMeAct(Ihandle *dmy) {
> 		sayHit();
> 		return 0;
> 	}
> }
>
> I have also tried it with hitMeAct being a D function instead of extern(C).
>
> It is as if the	call to IupSetCallback is interpreting hitMeAct to be a property function and that the call was meant to be:
>
> 	IupSetCallback(btn,"ACTION",hitMeAct());
>
> It there someway to force D to consider the hitMeAct parameter to be passing a function and NOT calling it?  I tried prefixing a & - no go.
>
> Would welcome any hints.
>
> Yes I have already looked at the .d files purporting to provide access to IUP.
> And a more or less equivalent C program works fine.


Why is it that prefixing it with '&' does not work?  Am I safe in assuming that it then complains about hitMeAct being not callable with parameters ()?  In which case, try currying it:

import std.functional : curry;
IupSetCallback(btn, "ACTION", &curry!(hitMeAct, dmy));

On Wednesday, 19 March 2014 at 02:21:18 UTC, James Wirth wrote:
> When trying to associate an Icallback function to a button in the IUP GUI
> API using the IupSetCallback function, the D compiler seems to insist on evaluating that callback in order to pass its value rather than passing the function itself.
>
> I get this dmd compiler error (the source is named hitmeiup.d) :
>
> Error: function hitmeiup.hitMeAct (Ihandle_* dmy) is not callable using argument types ()
> hitmeiup.d(41): Error: expected 1 function arguments, not 0
>
> for this line calling the IupSetCallback:
>
> 	IupSetCallback(btn,"ACTION",hitMeAct);
>
> The callback function was named hitMeAct as follows:
>
> extern(C) {
> 	int hitMeAct(Ihandle *dmy) {
> 		sayHit();
> 		return 0;
> 	}
> }
>
> I have also tried it with hitMeAct being a D function instead of extern(C).
>
> It is as if the	call to IupSetCallback is interpreting hitMeAct to be a property function and that the call was meant to be:
>
> 	IupSetCallback(btn,"ACTION",hitMeAct());
>
> It there someway to force D to consider the hitMeAct parameter to be passing a function and NOT calling it?  I tried prefixing a & - no go.
>
> Would welcome any hints.
>
> Yes I have already looked at the .d files purporting to provide access to IUP.
> And a more or less equivalent C program works fine.

Using & to get the function pointer is correct in this case.
You may need to do a cast for the pointer to what c expects. However it will work fine.
The brackets forces it to call it. Don't.