[m-users.] Determinism woes...

[emacstheviking]

To paraphrase Neo, "I know Prolog".

but I don't know Mercury and I am struggling to figure out this error....I
am porting some old SWI code and it boils down to the fact that I obvuisly
don't truly understand what "det" means! Here is the code both as discrete
disjunctive clauses and a single big disjunct:

:- pred char_type(char::in, chartype::out) is det.

char_type(')', p_open).
char_type('(', p_close).
char_type(_, c_general).

char_type(C, T) :-
    (
        C = '(', T = p_open
    ;   C = ')', T = p_close
    ;   C = _,   T = c_general
    ).

and here is the compiler output:

fl1.m:049: In `char_type'(in, out):
fl1.m:049:   error: determinism declaration not satisfied.
fl1.m:049:   Declared `det', inferred `multi'.
fl1.m:056:   Disjunction has multiple clauses with solutions.

Now...I understand why (I think) this happens: it's because the final
matching disjuny can match more than one character value hence the multiple
(multi) classification by the compiler BUT he calling loop seeks merely to
convert a character into a character type.

Is this "cc_multi" in disguise as if the character is not one of the ones
explicitly tested for then I will commit to the first choice as it will be
a "general" character i.e. one with no special meaning to my little lexer.

Thank you,
Sean.
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