[mercury-users] constrained polymorphic mode error

[Tom Schrijvers]

On Mon, 12 Aug 2002, David Overton wrote:

> On Fri, Aug 09, 2002 at 08:14:18PM +0200, Tom Schrijvers wrote:
> I've just committed a fix for this bug which should appear in the next
> ROTD.

Yes, thank you, the bug is fixed in the rotd of 08-15-2002.

I have now run into another error message concerning contrained
polymorphic modes in this unstable rotd.
I think the real error  is the one saying that 'argument 1 became too
instantiated'. To me it looks similar to the previous bug, i.e. the
expected instantiatedness is more general than the inferred one.
Do you think this is a bug in the compiler or did I do something wrong?

Thanks for all the help,

Tom

Here's the error message:

[tom at ender closure]$ mmc closure2.m -E
closure2.m:067: In clause for `map(in(closure2:fun_closure((X =< ground),
(Y =< ground))), in(closure2:val_closure(closure2:closure_list((X =<
ground)))), out(closure2:val_closure(closure2:closure_list((Y =<
ground)))))':
closure2.m:067:   mode error in conjunction. The next 4 error messages
closure2.m:067:   indicate possible causes of this error.
closure2.m:066: In clause for `map(in(closure2:fun_closure((X =< ground),
(Y =< ground))), in(closure2:val_closure(closure2:closure_list((X =<
ground)))), out(closure2:val_closure(closure2:closure_list((Y =<
ground)))))':
closure2.m:066:   mode error in unification of `NCTC' and
`closure2:val_closure(V_12)'.
closure2.m:066:   Variable `NCTC' has instantiatedness `free',
closure2.m:066:   term `closure2:val_closure(V_12)'
closure2.m:066:   has instantiatedness `closure2:val_closure(free)'.
closure2.m:066: In clause for `map(in(closure2:fun_closure((X =< ground),
(Y =< ground))), in(closure2:val_closure(closure2:closure_list((X =<
ground)))), out(closure2:val_closure(closure2:closure_list((Y =<
ground)))))':
closure2.m:066:   mode error: argument 1 became too instantiated.
closure2.m:066:   Final instantiatedness of `V_20' was
`bound(closure2:list((Y =< ground), bound(closure2:val_closure((pred((free
-> bound(closure2:list((Y =< ground),
bound(closure2:val_closure((pred((free -> ...)) is det)))) ;
(closure2:nil)))) is
det)))) ; (closure2:nil))',
closure2.m:066:   expected final instantiatedness was `(X =< ground)'.
closure2.m:067: In clause for `map(in(closure2:fun_closure((X =< ground),
(Y =< ground))), in(closure2:val_closure(closure2:closure_list((X =<
ground)))), out(closure2:val_closure(closure2:closure_list((Y =<
ground)))))':
closure2.m:067:   mode error in unification of `RCL' and
`closure2:val_closure(V_14)'.
closure2.m:067:   Variable `RCL' has instantiatedness `free',
closure2.m:067:   term `closure2:val_closure(V_14)'
closure2.m:067:   has instantiatedness `closure2:val_closure(free)'.
closure2.m:067: In clause for `map(in(closure2:fun_closure((X =< ground),
(Y =< ground))), in(closure2:val_closure(closure2:closure_list((X =<
ground)))), out(closure2:val_closure(closure2:closure_list((Y =<
ground)))))':
closure2.m:067:   in argument 1 of functor `val_closure/1':
closure2.m:067:   mode error: variable `NCTC' has instantiatedness `free',
closure2.m:067:   expected instantiatedness for non-local variables
closure2.m:067:   of lambda goals is `ground'.

(maybe now that you are introducing constrained polymorphic modes
 you could changes this last error message to:

   expected instantiatedness for non-local variables
   of lambda goals is `X =< ground'.

  ;)

)

and here's the code:

:- module closure2.

:- interface.

:- import_module io.

:- type fun_closure(X,Y)
        ---> fun_closure(pred(X,Y)).

:- type val_closure(X)
        ---> val_closure(pred(X)).

:- type closure_list(X)
        ---> nil
	;    list(X,val_closure(closure2__closure_list(X))).

:- inst fun_closure(X,Y)
        == bound( closure2__fun_closure(pred(in(X),out(Y)) is det) ).

:- inst val_closure(X)
        == bound( closure2__val_closure(pred(out(X)) is det) ).

:- inst closure_list(X)
        == bound( closure2__nil
 	        ; closure2__list(X,closure2__val_closure(closure2__closure_list(X)))
 		).

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

:- implementation.

:- import_module int.

:- pred eval(val_closure(X),X).
:- mode eval(in(val_closure(X =< ground)),out(X =< ground)) is det.
eval(val_closure(P),X) :-
   call(P,X).

:- pred eval2(pred(val_closure(X)),X).
:- mode eval2(pred(out(val_closure(X =< ground))) is det,out(X =< ground)) is det.
eval2(P,R) :-
  call(P,X),
  eval(X,R).

:- pred apply(fun_closure(X,Y),X,Y).
:- mode apply(in(fun_closure(X =< ground,Y =< ground)),in(X =< ground),out(Y =< ground)) is det.
apply(fun_closure(P),X,Y) :-
   call(P,X,Y).


:- pred map(fun_closure(X,Y),
            val_closure(closure_list(X)),
	    val_closure(closure_list(Y))).
:- mode map(in(fun_closure(X =< ground,Y =< ground)),
            in(val_closure(closure_list(X =< ground))),
	    out(val_closure(closure_list(Y =< ground)))) is det.
map(FC,CCL,RCL) :-
   eval(CCL,CL),
   ( CL = list(H,CTC) ->
       apply(FC,H,NH),
       NCTC = val_closure(eval2(map(FC,CTC))),
       RCL = val_closure(closure_list_list(NH,NCTC))
   ;
       RCL = val_closure(closure_list_nil)
   ).

:- pred closure_list_nil(closure_list(X)).
:- mode closure_list_nil(out(closure_list(X))) is det.
closure_list_nil(nil).

:- pred closure_list_list(X,val_closure(closure_list(X)),closure_list(X)).
:- mode closure_list_list(in(X =< ground),
                          in(val_closure(closure_list(X =< ground))),
			  out(closure_list(X =< ground))) is det.
closure_list_list(H,CT,list(H,CT)).


:- pred twice(int::in,int::out) is det.
twice(X,Y) :-
   Y is X * 2.

:- pred test(val_closure(closure_list(int))).
:- mode test(out(val_closure(closure_list(ground)))) is det.
test(R) :-
   P = (pred(N::out(closure_list(ground))) is det :- N = nil),
   map(fun_closure(twice),val_closure(P),R).

main -->
         {test(R)},
	 io__write(R),
	 io__nl
	 .

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