Call on determinate

Author(s): José Morales, Manuel Carro.

Version: 1.7#149 (2001/11/19, 19:17:51 CET)

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 (det_hook_rt)
• Documentation on exports (det_hook_rt)
• Documentation on internals (det_hook_rt)
• Other information (det_hook_rt)
• Known bugs and planned improvements (det_hook_rt)

Usage and interface (det_hook_rt)

Documentation on exports (det_hook_rt)

PREDICATE: det_try/3:

Meta-predicate with arguments: det_try(goal,goal,goal).

Usage: det_try(Goal, OnCut, OnFail)

• Description: Action is called, and OnCut and OnFail are goals to be executed when Goal is cut or when it finitely fails, respectively. In order for this to work, cutting must be performed in a special way, by using the !!/0 predicate, also provided by this module.
• The following properties should hold at call time: Goal is a term which represents a goal, i.e., an atom or a structure. (basic_props:callable/1) OnCut is a term which represents a goal, i.e., an atom or a structure. (basic_props:callable/1) OnFail is a term which represents a goal, i.e., an atom or a structure. (basic_props:callable/1)

Documentation on internals (det_hook_rt)

PREDICATE: !!/0:

Usage:

• Description: Performs a special cut which prunes alternatives away, as the usual cut, but which also executes the goals specified as OnCut for any call in the scope of the cut.

Other information (det_hook_rt)

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 (det_hook_rt)

• 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.

Go to the first, previous, next, last section, table of contents.