[mercury-users] Det/Semidet

Nigel Evans bignigeuk at gmail.com
Sat Dec 9 00:38:04 AEDT 2006

I am new to mercury and i am having a problem with determinism. I know main
cannot be semidet, but how can i switch the code around so that the
following example compiles? Any help would be greatly appreciated.

:- module marray.

:- interface.

:- import_module io.

:- pred main(io::di, io::uo) is det.

:- implementation.

:- import_module list, string, array2d, int.

main(!IO) :-
    new(5,5,["XXX"]) = MyArray,
    MyList = ["the","cat","chased","the","dog"],
    add_input_string(MyList,MyArray, 0).

:- pred add_input_string(list(string)::in,
array2d(list(string))::array2d_di, int::in) is semidet.
add_input_string(TheList, Array, Number) :-
    TheList = [Head|Tail],
    ( Array ^ elem(0,Number) := [Head] ) = T3,
    NextNumber is Number + 1,

C:\Documents and Settings\Nige\Desktop>mmc --make -E marray
Making Mercury\cs\marray.c
marray.m:007: In `main(di, uo)':
marray.m:007:   error: determinism declaration not satisfied.
marray.m:007:   Declared `det', inferred `semidet'.
marray.m:016:   call to `add_input_string(in, (array2d.array2d_di), in)' can
Error: system command received signal 1.
** Error making `Mercury\cs\marray.c'.


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