Re: Ann: SWI-Prolog 7.1.0

An indexing optimization I would like:
p(F,...) :- functor(F, t, _), !, ....
q(F,...) :- F=t(A,_,_,_,C), !, ....

My reason for coding like this is I want to pass F to subsequent predicates.

Alan Baljeu

On 2013-12-11, at 6:21 AM, Nicos Angelopoulos (Univ of York) <[email protected]> wrote:

> 
> Dear Jan,
> 
>> I am unsure.  I haven't seen that many cases where switching on the 
>> native type is crucial performance-wise and as we have seen here,
>> the application types are often not a one-to-one mapping from the
>> system types.  It is easy enough to write a term_type/2 doing the
>> right thing for the real library.  If it proves to be too slow, we
>> can always consider adding leading type checks to the clause indexing,
>> such that you can write your (application specific) term_type/2 more
>> efficiently.
>> 
>>    Cheers --- Jan
> 
>    As i said I am unsure myself.
>    term_type/2 though, seems to have an intuitive reading and be benign. 
>    In the cases that it is useful it can be used in combination with
>    Prolog's indexing to produce readable and computationally, well behaved
>        code with no extra gimmicks.
>    I am currently fascinated by indexing, so my lenses are tinted.
>        The other argument I can see against term_type/2 is that somehow it has
>        to have a special status/meaning when called with 2 variables as arguments. 
> 
>        Of course I know how to implement it in Prolog, 
>        as I know how to implement append/3 (I think).
>        Efficiency though, can be measured in many ways. 
>        Using well understood basic constructs that are known to all, allows us to
>        efficiently produce efficient programs that are easy to follow and maintain
>        by us and others. Think append/3 again.
> 
>        The best thing to do it would seem to be to leave this in the back burner
>    and add it if you later on find other places it might be useful. 
> 
> Regards,
> 
> Nicos
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