Re: Dup Foo?

> Hello,
>
> I am curious whether there is an easier way to find duplicate fact
> instances along with the "duplication count" than the one I have come up
> with.
>
> I have a fairly simple solution, but feel there should be something less
> "convoluted" than my solution.
>
> An example, I think best explains this:
>
> foo(a,aa).
> foo(a,ac).
> foo(a,aa).
> foo(b,aa).
> foo(b,xy).
> foo(b,xy).
> foo(b,xy).
> foo(b,ac).
> foo(b,aa).
>
> foo(X,Y,1) :- foo(X,Y).
>
> dupfoo(X,Y,C) :-
>     bagof(Z,foo(X,Y,Z),L), length(L,C), C>1.
>
> The goal is to locate the cases where foo(X,Y) produces multiple identical
> solutions.
>
> My definition for dupfoo(X,Y,C) shown above gives the correct results on
> backtracking.  Namely:
>
> ?- dupfoo(X,Y,C).
> X = a,
> Y = aa,
> C = 2 ;
> X = b,
> Y = aa,
> C = 2 ;
> X = b,
> Y = xy,
> C = 3.
>
> What I don't like, in particular, is that I had to create the foo/3
> predicate whose only function is to assist in collecting the duplicate
> count (C).  It seems to me that there should be some way to make use of the
> bagof predicate without having to make use of the foo/3 predicate.