[mercury-users] Mode checking bug

[Peter Hawkins]

Hi...

The following program produces this mode error, whereas I think it  
should mode check fine (compiler ROTD 2006-06-26):
test.m:022: In clause for `'__Unify__'((unique(test.lterm(ground,
test.m:022:   unique(test.lterm(free, ground)))) >> bound(test.lterm 
(ground,
test.m:022:   bound(test.lterm(ground, ground))))), (ground >>
test.m:022:   bound(test.lterm(ground, bound(test.lterm(ground,  
ground))))))':
test.m:022:   mode error in unification of `HeadVar__1' and  
`test.lterm(V_9,
test.m:022:   V_10)'.
test.m:022:   Variable `HeadVar__1' has instantiatedness
test.m:022:   `unique(test.lterm(ground, unique(test.lterm(free,  
ground))))',
test.m:022:   term `test.lterm(V_9, V_10)' has instantiatedness  
`test.lterm(
test.m:022:     free,
test.m:022:     free
test.m:022:   )'.


:- module test.
:- interface.
:- implementation.

:- type pp ---> lterm(int, pp).

:- pred foo(pp::out, pp::out, int::out) is nondet.
:- pred bar(pp::out, pp::out, int::out) is nondet.

foo(_, _, _) :- fail.

bar(P0, lterm(PH, P1), E) :-
     foo(P0, lterm(PH, P1), E),
     foo(P0, lterm(PH, lterm(_, P1)), E).



But if I replace the clause for bar with the following equivalent  
clause, the code mode checks fine.
bar(P0, lterm(PH, P1), E) :-
     foo(P0, lterm(PH, P1), E),
     foo(P0, Temp, E),
     Temp = lterm(PH, lterm(_, P1)).

Please fix?

Cheers,
Peter
--------------------------------------------------------------------------
mercury-users mailing list
post:  mercury-users at cs.mu.oz.au
administrative address: owner-mercury-users at cs.mu.oz.au
unsubscribe: Address: mercury-users-request at cs.mu.oz.au Message: unsubscribe
subscribe:   Address: mercury-users-request at cs.mu.oz.au Message: subscribe
--------------------------------------------------------------------------