• Daniel Keep (22/22) Jan 17 2007 Hey there, I'm having problems with getting the return type of a
• Kirk McDonald (12/42) Jan 17 2007 ReturnType has two forms: One which is intended to operate on a function...
• Daniel Keep (21/65) Jan 17 2007 template SDL_Refcall(alias tFn)
• Kirk McDonald (18/89) Jan 17 2007 I have two thoughts:
• Daniel Keep (9/103) Jan 17 2007 Well, since I'm using Derelict, there isn't a huge amount I can do...

Daniel Keep <daniel.keep+lists gmail.com> writes:

Hey there, I'm having problems with getting the return type of a 
function pointer.  Basically, I want to do this:

template SDL_SafeCall(alias tFn)
{
     ReturnType!(SDL_SetVideoMode) SDL_SafeCall(...)
     {
         ...
     }
}
SDL_SafeCall!(SDL_SetVideoMode)(...);

where SDL_SetVideoMode is declared like so (yes, it's DerelictSDL):

typedef SDL_Surface* function(int,int,int,Uint32) pfSDL_SetVideoMode;
pfSDL_SetVideoMode          SDL_SetVideoMode;

When I try to compile my code, I get the following errors:

C:\Daniel\dmd\dmd\src\phobos\std\traits.d(34): alias 
std.traits.ReturnType!(pfSDL_SetVideoMode).ReturnType recursive alias 
declaration
C:\Daniel\dmd\dmd\src\phobos\std\traits.d(34): template instance 
std.traits.ReturnType!(pfSDL_SetVideoMode) error instantiating

I've tried writing my own version, but that didn't do any better. 
Anyone have any ideas?

	-- Daniel

Kirk McDonald <kirklin.mcdonald gmail.com> writes:

Daniel Keep wrote:
 
 Hey there, I'm having problems with getting the return type of a 
 function pointer.  Basically, I want to do this:
 
 template SDL_SafeCall(alias tFn)
 {
     ReturnType!(SDL_SetVideoMode) SDL_SafeCall(...)
     {
         ...
     }
 }
 SDL_SafeCall!(SDL_SetVideoMode)(...);
 
 where SDL_SetVideoMode is declared like so (yes, it's DerelictSDL):
 
 typedef SDL_Surface* function(int,int,int,Uint32) pfSDL_SetVideoMode;
 pfSDL_SetVideoMode          SDL_SetVideoMode;
 
 When I try to compile my code, I get the following errors:
 
 C:\Daniel\dmd\dmd\src\phobos\std\traits.d(34): alias 
 std.traits.ReturnType!(pfSDL_SetVideoMode).ReturnType recursive alias 
 declaration
 C:\Daniel\dmd\dmd\src\phobos\std\traits.d(34): template instance 
 std.traits.ReturnType!(pfSDL_SetVideoMode) error instantiating
 
 I've tried writing my own version, but that didn't do any better. Anyone 
 have any ideas?
 
     -- Daniel

ReturnType has two forms: One which is intended to operate on a function 
pointer or delegate /type/, and one which is intended to operate on a 
function alias.

SDL_SetVideoMode is a function pointer. You want to pass its /type/ to 
ReturnType. By passing it directly, it gets sent to the alias form of 
ReturnType, which confuses it greatly. Try this:

ReturnType!(typeof(SDL_SetVideoMode))

-- 
Kirk McDonald
Pyd: Wrapping Python with D
http://pyd.dsource.org

Daniel Keep <daniel.keep+lists gmail.com> writes:

Kirk McDonald wrote:
 Daniel Keep wrote:
 
 Hey there, I'm having problems with getting the return type of a 
 function pointer.  Basically, I want to do this:

 template SDL_SafeCall(alias tFn)
 {
     ReturnType!(SDL_SetVideoMode) SDL_SafeCall(...)
     {
         ...
     }
 }
 SDL_SafeCall!(SDL_SetVideoMode)(...);

 where SDL_SetVideoMode is declared like so (yes, it's DerelictSDL):

 typedef SDL_Surface* function(int,int,int,Uint32) pfSDL_SetVideoMode;
 pfSDL_SetVideoMode          SDL_SetVideoMode;

 When I try to compile my code, I get the following errors:

 C:\Daniel\dmd\dmd\src\phobos\std\traits.d(34): alias 
 std.traits.ReturnType!(pfSDL_SetVideoMode).ReturnType recursive alias 
 declaration
 C:\Daniel\dmd\dmd\src\phobos\std\traits.d(34): template instance 
 std.traits.ReturnType!(pfSDL_SetVideoMode) error instantiating

 I've tried writing my own version, but that didn't do any better. 
 Anyone have any ideas?

     -- Daniel

 
 
 ReturnType has two forms: One which is intended to operate on a function 
 pointer or delegate /type/, and one which is intended to operate on a 
 function alias.
 
 SDL_SetVideoMode is a function pointer. You want to pass its /type/ to 
 ReturnType. By passing it directly, it gets sent to the alias form of 
 ReturnType, which confuses it greatly. Try this:
 
 ReturnType!(typeof(SDL_SetVideoMode))
 

template SDL_Refcall(alias tFn)
{ // line 57
     ReturnType!(typeof(tFn)) SDL_Refcall(tArgs...)(tArgs args)
     {
         ReturnType!(typeof(tFn)) r = tFn(args);
         if( r is null )
             throw new SDLException(tFn.nameof, 0);
         else
             return r;
     }
}

SDL_Refcall!(SDL_SetVideoMode)(...);

No good.

C:\Daniel\dmd\dmd\src\phobos\std\traits.d(34): alias 
std.traits.ReturnType!(pfSDL_SetVideoMode).ReturnType recursive alias 
declaration
C:\Daniel\dmd\dmd\src\phobos\std\traits.d(58): template instance 
std.traits.ReturnType!(pfSDL_SetVideoMode) error instantiating
src\engine\shared_sdl\shared_sdl.d(58): Error: 
ReturnType!(pfSDL_SetVideoMode) is used as a type

Kirk McDonald <kirklin.mcdonald gmail.com> writes:

Daniel Keep wrote:
 Kirk McDonald wrote:
 
 Daniel Keep wrote:

 Hey there, I'm having problems with getting the return type of a 
 function pointer.  Basically, I want to do this:

 template SDL_SafeCall(alias tFn)
 {
     ReturnType!(SDL_SetVideoMode) SDL_SafeCall(...)
     {
         ...
     }
 }
 SDL_SafeCall!(SDL_SetVideoMode)(...);

 where SDL_SetVideoMode is declared like so (yes, it's DerelictSDL):

 typedef SDL_Surface* function(int,int,int,Uint32) pfSDL_SetVideoMode;
 pfSDL_SetVideoMode          SDL_SetVideoMode;

 When I try to compile my code, I get the following errors:

 C:\Daniel\dmd\dmd\src\phobos\std\traits.d(34): alias 
 std.traits.ReturnType!(pfSDL_SetVideoMode).ReturnType recursive alias 
 declaration
 C:\Daniel\dmd\dmd\src\phobos\std\traits.d(34): template instance 
 std.traits.ReturnType!(pfSDL_SetVideoMode) error instantiating

 I've tried writing my own version, but that didn't do any better. 
 Anyone have any ideas?

     -- Daniel



 ReturnType has two forms: One which is intended to operate on a 
 function pointer or delegate /type/, and one which is intended to 
 operate on a function alias.

 SDL_SetVideoMode is a function pointer. You want to pass its /type/ to 
 ReturnType. By passing it directly, it gets sent to the alias form of 
 ReturnType, which confuses it greatly. Try this:

 ReturnType!(typeof(SDL_SetVideoMode))

 
 template SDL_Refcall(alias tFn)
 { // line 57
     ReturnType!(typeof(tFn)) SDL_Refcall(tArgs...)(tArgs args)
     {
         ReturnType!(typeof(tFn)) r = tFn(args);
         if( r is null )
             throw new SDLException(tFn.nameof, 0);
         else
             return r;
     }
 }
 
 SDL_Refcall!(SDL_SetVideoMode)(...);
 
 No good.
 
 C:\Daniel\dmd\dmd\src\phobos\std\traits.d(34): alias 
 std.traits.ReturnType!(pfSDL_SetVideoMode).ReturnType recursive alias 
 declaration
 C:\Daniel\dmd\dmd\src\phobos\std\traits.d(58): template instance 
 std.traits.ReturnType!(pfSDL_SetVideoMode) error instantiating
 src\engine\shared_sdl\shared_sdl.d(58): Error: 
 ReturnType!(pfSDL_SetVideoMode) is used as a type

I have two thoughts:

pfSDL_SetVideoMode is declared as a typedef. Maybe try it as an alias? 
ReturnType just uses the "return" TypeSpecialization in the 
IsExpression, which might get confused by typedefs. (I have not tested 
this.)

Second, you are passing in a (global?) variable as a template alias 
parameter. While this is technically allowed, I have had nothing but 
grief doing that sort of thing. I suggest re-writing it as:

ReturnType!(fn_t) SDL_Refcall(fn_t, tArgs ...) (fn_t fn, tArgs args) {
     // stuff...
}

And then calling it as a regular function template:

SDL_Refcall(SDL_SetVideoMode, ...);

-- 
Kirk McDonald
Pyd: Wrapping Python with D
http://pyd.dsource.org

Daniel Keep <daniel.keep+lists gmail.com> writes:

Kirk McDonald wrote:
 Daniel Keep wrote:
 
 Kirk McDonald wrote:

 Daniel Keep wrote:

 Hey there, I'm having problems with getting the return type of a 
 function pointer.  Basically, I want to do this:

 template SDL_SafeCall(alias tFn)
 {
     ReturnType!(SDL_SetVideoMode) SDL_SafeCall(...)
     {
         ...
     }
 }
 SDL_SafeCall!(SDL_SetVideoMode)(...);

 where SDL_SetVideoMode is declared like so (yes, it's DerelictSDL):

 typedef SDL_Surface* function(int,int,int,Uint32) pfSDL_SetVideoMode;
 pfSDL_SetVideoMode          SDL_SetVideoMode;

 When I try to compile my code, I get the following errors:

 C:\Daniel\dmd\dmd\src\phobos\std\traits.d(34): alias 
 std.traits.ReturnType!(pfSDL_SetVideoMode).ReturnType recursive 
 alias declaration
 C:\Daniel\dmd\dmd\src\phobos\std\traits.d(34): template instance 
 std.traits.ReturnType!(pfSDL_SetVideoMode) error instantiating

 I've tried writing my own version, but that didn't do any better. 
 Anyone have any ideas?

     -- Daniel




 ReturnType has two forms: One which is intended to operate on a 
 function pointer or delegate /type/, and one which is intended to 
 operate on a function alias.

 SDL_SetVideoMode is a function pointer. You want to pass its /type/ 
 to ReturnType. By passing it directly, it gets sent to the alias form 
 of ReturnType, which confuses it greatly. Try this:

 ReturnType!(typeof(SDL_SetVideoMode))

 template SDL_Refcall(alias tFn)
 { // line 57
     ReturnType!(typeof(tFn)) SDL_Refcall(tArgs...)(tArgs args)
     {
         ReturnType!(typeof(tFn)) r = tFn(args);
         if( r is null )
             throw new SDLException(tFn.nameof, 0);
         else
             return r;
     }
 }

 SDL_Refcall!(SDL_SetVideoMode)(...);

 No good.

 C:\Daniel\dmd\dmd\src\phobos\std\traits.d(34): alias 
 std.traits.ReturnType!(pfSDL_SetVideoMode).ReturnType recursive alias 
 declaration
 C:\Daniel\dmd\dmd\src\phobos\std\traits.d(58): template instance 
 std.traits.ReturnType!(pfSDL_SetVideoMode) error instantiating
 src\engine\shared_sdl\shared_sdl.d(58): Error: 
 ReturnType!(pfSDL_SetVideoMode) is used as a type

 
 
 I have two thoughts:
 
 pfSDL_SetVideoMode is declared as a typedef. Maybe try it as an alias? 
 ReturnType just uses the "return" TypeSpecialization in the 
 IsExpression, which might get confused by typedefs. (I have not tested 
 this.)

Well, since I'm using Derelict, there isn't a huge amount I can do... 
ok; I *could* go and change all instances of 'typedef' to 'alias'... 
might actually do that and see what happens (but I'd prefer to stick to 
an unmodified version if at all possible).

 Second, you are passing in a (global?) variable as a template alias 
 parameter. While this is technically allowed, I have had nothing but 
 grief doing that sort of thing. I suggest re-writing it as:
 
 ReturnType!(fn_t) SDL_Refcall(fn_t, tArgs ...) (fn_t fn, tArgs args) {
     // stuff...
 }
 
 And then calling it as a regular function template:
 
 SDL_Refcall(SDL_SetVideoMode, ...);
 

Aww... but the old way was so much purtier...

Anyway, I'll give these a try once I've sufficiently woken up, and let 
you know how it goes.

	-- Daniel