[mercury-users] unification problem

[Stefan Hinterstoisser]

Hi!

I have the following predicate:

:- pred konto( string, string, string, string ).
:- mode konto( in, in, out, out ) is nondet.
:- mode konto( out, in, out, out ) is nondet.
:- mode konto( in,  out, out, out ) is nondet.
:- mode konto( out, out, out, out ) is nondet.
konto( "Vater", "Mutter", "true", "konto(Vater,Mutter);" ).
konto( _, _, "false", "konto(false,false)" ).

what I want is that this predicate (although definied as nondet) behaves
like a predicate that always becomes true (and gave true and konto(Vater,
Mutter) back if it matches Vater and Mutter and else false and
konto(false,false) ). unfortunatly the wildcards dont fit because of missing
groundness (because of the mode definition). is there any way to get that
demanded behavior I described before without changing the modes (and note:
every mode type could also be used in the later program!)....I tried it with
if and else but than I get a scope error (because Mercury is not able to
bind a Variable in if else function - but that is demanded because of the
mode declarations.... what can I do???
Thanx in advance,
Stefan

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