Re: goal_expansion

Hi Jonathon

From my self-learner experience (mainly
lifter<https://github.com/CapelliC/prolog-snippets/blob/master/lifter.pl>)
I have an hint - maybe useful only if you use XPCE IDE - or anything
similar...
I think you'll need to place near bottom of source a condition

:- multifile user:goal_expansion/2.
user:goal_expansion(X, Y) :-
	\+ current_prolog_flag(xref, true),
	... your_code

Indeed, I experienced IDE freezing with a 'cross-referencing buffers'
message before I discovered that trick - in library(clpfd), if I recall
rightly.

bye Carlo



2014-02-09 1:46 GMT+01:00 Jonathon Doran <[email protected]>:

> I would very much like to see a simple example of the use of
> goal_expansion.
>
> I have a large program, and I would like to make a series of changes.  I
> see that I am following the same pattern each time, and if I were writing
> in another language I would consider creating a macro.
>
> This may be the wrong technique to use in Prolog, but I'm curious if it
> would be possible.
>
> For example:  A list is passed to a predicate, and the list is checked for
> an optional member (may or may not be there).  If the member is in the
> list, we use it.  If not, a default value is used.
>
> Writing the code by hand I might do:
>
>    (
>       \+ member(color:Color, List) ->
>              random_color(Color)
>        ;
>              true
>    ),
>
>
> I am wondering if I can clean that up to something more readable via
> goal expansion.
>
> (This may be a dumb way to go about things, but I would rather not rewrite
>  a huge chunk of existing code)
>
> Thanks,
> Jonathon Doran
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