I am stuck with a really wierd problem around some code that used to work just fine and I am at a loss to explain what is happening. A long time back I published on github a comprehensive binding to SDL2 for gprolog, it all worked on ubuntu and OSX just fine.
A year or two down the line, I checked out the code, it built first time
but it is raising existence_error-s on code that exists BUT ARITY IS ZERO.
I have an event loop predicate that calls itself until you hit the ESC
key... here is what it looks like trying to run the fonttest predicate:
*?- [f].*
*?- fonttest.*
Window flags: 0
gp_SDL_CreateWindow: ok: 0x3e10390
SDL.PL: gp_SDL_CreateRenderer_C(65078160, -1, 6, Rndr).
render draw color: 0, 0, 0
Font texture: 480 x 95 pixels
render draw color: 255, 128, 128
render draw color: 0, 128, 128
window(213,2,shown)
uncaught exception:
error(existence_error(procedure,handle_event/0),evloop/0)
*at this point...* I listed the handle_event predicate, the code is there
BUT NOT /0...
*| ?- listing(handle_event)*.
% file: /home/sean/Documents/prolog/gnuprolog-libsdl2/f.pl
handle_event(quit(_)) :-
format([81, 85, 73, 84, 32, 115, 101, 108, 101, 99, 116, 101, 100, 126,
110], []), !,
fail.
handle_event(keyup(_, _, released, _, _, 27, _)) :-
format([69, 83, 67, 32, 112, 114, 101, 115, 115, 101, 100, 126, 110],
[]), !,
fail.
handle_event(_).
*and finally I listed out the evloop predicate to check:*
| ?- listing(evloop).
% file: /home/sean/Documents/prolog/gnuprolog-libsdl2/f.pl
evloop :-
sdl_PollEvent(A),
handle_event(A), !,
evloop.
evloop.
evloop(A) :-
call(A),
sdl_PollEvent(B),
handle_event(B), !,
evloop(A).
evloop(_).
There IS evloop/0 but there is NO handle_event/0 ... why does it think
there is??? I haven't managed to get over this yet!
I have attached the fill source code of the test.
Thanks
Sean.
f.pl
Description: Perl program
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