mirror of
https://github.com/Mercury-Language/mercury.git
synced 2026-04-15 09:23:44 +00:00
42 lines
903 B
Mathematica
42 lines
903 B
Mathematica
%---------------------------------------------------------------------------%
|
|
% vim: ts=4 sw=4 et ft=mercury
|
|
%---------------------------------------------------------------------------%
|
|
|
|
:- module contravariance_bug.
|
|
:- interface.
|
|
:- import_module io.
|
|
|
|
:- pred main(io::di, io::uo) is det.
|
|
|
|
:- implementation.
|
|
|
|
:- import_module bool.
|
|
:- import_module list.
|
|
|
|
main(!IO) :-
|
|
( if q(p) then
|
|
io.write_string("yes\n", !IO)
|
|
else
|
|
io.write_string("no\n", !IO)
|
|
).
|
|
|
|
:- type intlist == list(int).
|
|
:- inst nonempty
|
|
---> [ground | list].
|
|
:- inst list
|
|
---> [ground | list]
|
|
; [].
|
|
|
|
:- pred p(intlist, intlist).
|
|
:- mode p((list >> nonempty), (free >> nonempty)) is semidet.
|
|
|
|
p([X], [X]).
|
|
p([X, Y | Zs], [Y, X | Zs]).
|
|
|
|
:- pred q(pred(intlist, intlist)).
|
|
:- mode q(pred((nonempty >> nonempty), (free >> list)) is semidet) is semidet.
|
|
|
|
q(P) :-
|
|
P([1], L),
|
|
L \= [].
|