RE: if

[Calum Grant]

A simpler variant of this problem is

        insert_set(H, L, L) :- member(H, L), !.  % A "hack" according to FH
        insert_set(H, L, [H|L]).

which takes an item H and inserts it into a list L without duplicates, like
a simple set.  The second clause should only be applied if the first one
fails.  Therefore the ! is necessary.  This can be rewritten as

        insert_set(H, S0, S) :-
        (
                member(H, S0) -> S0=S;  % A "hack" according to RS
                S = [H|S0]
        ).

The difference is purely cosmetic, and I don't think it's worth arguing
about.  It's a bit like saying that "|" is better than ";".

Calum
--
  Calum Grant - address@hidden - 01223 569700

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> -----Original Message-----
> From: address@hidden [mailto:address@hidden
> Behalf Of Ron Stodden
> Sent: Tuesday, January 30, 2001 6:39 PM
> To: address@hidden
> Subject: Re: if
>
>
> Fergus Henderson wrote:
> >
> > How would you write something simple like the following code, then?
>
> Simple?   What is the underlying operation this tries to achieve -
> say, expressed in simple English?   It is not at all apparent.
>
> --
> Regards,
>
> Ron. [AU]
>
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