Call on determinate

Author(s): Jose F. Morales, Manuel Carro.

Offers an enriched variant of call and cut !!/0 which executes pending goals when the computation has no more alternatives.

This library is useful to, for example, get rid of external connections once the necessary data has been obtained.

Usage and interface

Other information

As an example, the program

:- module(_, _, [det_hook]).

enumerate(X):-
        display(enumerating), nl,
        OnCut = (display('goal cut'), nl),
        OnFail = (display('goal failed'), nl),
        det_try(enum(X), OnCut, OnFail).

enum(1).
enum(2).
enum(3).

behaves as follows:

?- enumerate(X).
enumerating

X = 1 ? ;

X = 2 ? ;

X = 3 ? ;
goal failed

(note the message inserted on failure). The execution can be cut as follows:

?- use_package(det_hook).
{Including /home/clip/lib/ciao/ciao-1.7/library/det_hook/det_hook.pl
}

yes
?- enumerate(X), '!!'.
enumerating
goal cut

X = 1 ? ;

no

Known bugs and planned improvements

  • If the started goals do not exhaust their solutions, and '!!'/0 is not used, the database will populate with facts which will be consulted the next time a '!!'/0 is used. This could cause incorrect executions.