[mercury-users] strange mmc behavior

[Holger Krug]

On Thu, Jul 26, 2001 at 07:32:33AM +1000, Fergus Henderson wrote:
> On 25-Jul-2001, Holger Krug <hkrug at rationalizer.com> wrote:
> > :- module lex.
> > 
> > :- implementation.
> > 
> > :- pred live_lexeme_in_accepting_state(list(live_lexeme(Tok)),
> >                 annotated_token(Tok)).
> > :- mode live_lexeme_in_accepting_state(in(live_lexeme_list),   
> > 	                  out(annotated_token)) is semidet.
> > 
> > live_lexeme_in_accepting_state([L | Ls], Token) :-    % line 412
> >     ( if in_accepting_state(L)                        % line 413
> >       then Token = L ^ clxm_token
> >       else live_lexeme_in_accepting_state(Ls, Token)  % line 415
> >     ).
> > 
> > If the called predicate `in_accepting_state' is placed in module `lex'
> > all works fine. Difficulties arise immediately when I place
> > `in_accepting_state' into the separate sub-module `lex__lexeme'. In
> > this case the following error occurs:
> > 
> > lex.m:415: In clause for `live_lexeme_in_accepting_state(in((lex:live_lexeme_list)), out((lex:annotated_token)))':
> > lex.m:415:   mode error in conjunction. The next 2 error messages
> > lex.m:415:   indicate possible causes of this error.
> > lex.m:413: In clause for `live_lexeme_in_accepting_state(in((lex:live_lexeme_list)), out((lex:annotated_token)))':
> > lex.m:413:   in argument 1 of call to predicate `lex:lexeme:in_accepting_state/1':
> > lex.m:413:   mode error: variable `L' has instantiatedness `bound((lex:lexeme):compiled_lexeme(bound((lex:ignore) ; lex:t((func((ground -> ground)) = (free -> ground) is det))), ground, ground))',
> > lex.m:413:   expected instantiatedness was `(lex:live_lexeme)'.
> > 
> > What is strange in that error message is that both modes:
> > `(lex:live_lexeme)'
> > and
> > `bound((lex:lexeme):compiled_lexeme(bound((lex:ignore) ; lex:t((func((ground -> ground)) = (free -> ground) is det))), ground, ground))'
> > are exactly the same !
> 
> Those are insts, not modes.

It was late yesterday.
 
> Are you sure they are the same?  You didn't post the definitions of the
> live_lexeme inst or the live_lexeme_list inst.

Here they are:

%---- file lex.m ------------------------------------------------------------- 

:- module lex.

:- interface.

:- inst token_creator == (func(in)=out is det).

:- inst annotated_token == bound( t(token_creator); ignore).

:- implementation.

:- include_module lex__lexeme.

:- inst live_lexeme == compiled_lexeme(annotated_token).

%---- file lex.lexeme.m ------------------------------------------------------ 

:- module lex__lexeme.

:- interface.

:- inst compiled_lexeme(Inst) ==
            bound(compiled_lexeme(Inst,ground,ground)).

%----------------------------------------------------------------------------- 

Additional remark:

The error message is inconsistent with the language reference in that `->'
is deprecated in favor of `>>' in mode declarations.


-- 
Holger Krug
hkrug at rationalizer.com
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