97 lines
2.0 KiB
Prolog
97 lines
2.0 KiB
Prolog
/**
|
|
* @file clauses.yap
|
|
* @author VITOR SANTOS COSTA <vsc@VITORs-MBP.lan>
|
|
* @date Tue Nov 17 14:51:30 2015
|
|
*
|
|
* @brief Utilities for clause manipulation.
|
|
*
|
|
*
|
|
*/
|
|
|
|
:- module(clauses,
|
|
[list2conj/2,
|
|
conj2list/2,
|
|
clauselength/2]).
|
|
|
|
%% @{
|
|
|
|
/**
|
|
* @defgroup clauses Clause Manipulation
|
|
* @ingroup library
|
|
|
|
This library supports a number of useful utilities that come up over and
|
|
over again when manipulating Prolog programs. This will include
|
|
operations and conversion to other structures.
|
|
|
|
@author Vitor Santos Costa
|
|
*/
|
|
|
|
/** conj2list( +Conj, -List) is det
|
|
Generate a list from a conjunction of literals.
|
|
|
|
It is often easier to apply operations on lists than on clauses
|
|
*/
|
|
conj2list( M:Conj, List ) :-
|
|
conj2list_( Conj, M, List, [] ).
|
|
|
|
conj2list( Conj, List ) :-
|
|
conj2list_( Conj, List, [] ).
|
|
|
|
|
|
conj2list_( C ) -->
|
|
{ var(C) },
|
|
!,
|
|
[C].
|
|
conj2list_( true ) --> !.
|
|
conj2list_( (C1, C2) ) -->
|
|
!,
|
|
conj2list_( C1 ),
|
|
conj2list_( C2 ).
|
|
conj2list_( C ) -->
|
|
[C].
|
|
|
|
conj2list_( C, M ) -->
|
|
{ var(C) },
|
|
!,
|
|
[M: C].
|
|
conj2list_( true , _) --> !.
|
|
conj2list_( (C1, C2), M ) -->
|
|
!,
|
|
conj2list_( C1, M ),
|
|
conj2list_( C2, M ).
|
|
conj2list_( C, M ) -->
|
|
{ strip_module(M:C, NM, NC) },
|
|
[NM:NC].
|
|
|
|
/** list2conj( +List, -Conj) is det
|
|
Generate a conjunction from a list of literals.
|
|
|
|
Notice Mthat this relies on indexing within the list to avoid creating
|
|
choice-points.
|
|
*/
|
|
list2conj([], true).
|
|
list2conj([Last], Last).
|
|
list2conj([Head,Next|Tail], (Head,Goals)) :-
|
|
list2conj([Next|Tail], Goals).
|
|
|
|
/** clauselength( +Clause, -Length) is det
|
|
Count the number of literals in a clause (head counts as one).
|
|
|
|
Notice that this is 1+length(conj2list), as we ignore disjunctions.
|
|
*/
|
|
clauselength( (_Head :- Conj), Length ) :-
|
|
clauselength( Conj, Length, 1 ).
|
|
|
|
|
|
clauselength( C, I1, I ) :-
|
|
{ var(C) },
|
|
!,
|
|
I1 is I+1.
|
|
clauselength( (C1, C2), I2, I ) :- !,
|
|
clauselength( C1, I1, I ),
|
|
clauselength( C2, I2, I1 ).
|
|
clauselength( _C, I1, I ) :-
|
|
I1 is I+1.
|
|
|
|
%%@}
|