Re: ASSERT in SWI Prolog

Nick Wedd wrote:
In message <ebrnrb$deo$1@xxxxxxxxxxxxxxxx>, russell kym horsell <kym@xxxxxxxxxxxxxxxxxxx> writes

Mika <miky821@xxxxxxxx> wrote:

I want to know if this can be made in SWI Prolog.

OK. The answer is "yes".

The answer to the question "is it pretty?", is -- of course -- "no".

It's not that ugly. Use bagof to collect all the facts into a list, process the list to replace fact2 by fact6, retractall the facts, and then assert the facts in the list. Though I can't imagine why anyone would want to do this.

Can't you imagine why anyone would wish to update
a large data structure without rewriting the entire
thing?!

Since the clauses of a functor *are* in a well-defined
order, and Prolog lets us exploit this (if we wish), it
could be useful (performance-wise) to be able to do this.

Indeed it seems inconsistent that we have asserta and
assertz but not a more general form. My guess is that
SWI-Prolog's database implementation is not amenable to
inserting any qty of clauses between two others, else
Jan would have added it by now :-)

More generally, it would be handy to be able to update
parts of a (large) fact in place...

Paul Singleton
.

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