terms.yap

/*************************************************************************
*                                    *
*    YAP Prolog                              *
*                                    *
*   Yap Prolog was developed at NCCUP - Universidade do Porto    *
*                                    *
* Copyright L.Damas, V.S.Costa and Universidade do Porto 1985-1997   *
*                                    *
**************************************************************************
*                                    *
* File:     terms.yap                        *
* Last rev: 5/12/99                          *
* mods:                                  *
* comments: Term manipulation operations                 *
*                                    *
*************************************************************************/
:- module(terms, [
          term_hash/2,
          term_hash/4,
          term_subsumer/3,
          instantiated_term_hash/4,
          variant/2,
          unifiable/3,
          subsumes/2,
 
          subsumes_chk/2,
          cyclic_term/1,
          variable_in_term/2,
          variables_within_term/3,
          new_variables_in_term/3
         ]).
 
 
/** @defgroup Terms Utilities On Terms
@ingroup YAPLibrary
@{
 
The next routines provide a set of commonly used utilities to manipulate
terms. Most of these utilities have been implemented in `C` for
efficiency. They are available through the
`use_module(library(terms))` command.
 
*/
/**
 @pred cyclic_term(? _Term_) 
 
Succeed if the argument  _Term_ is a cyclic term.
 
*/
 
 
/** @pred  term_subsumer(? _T1_, ? _T2_, ? _Subsumer_) 
 
Succeed if  _Subsumer_ unifies with the least general
generalization over  _T1_ and
 _T2_.
*/
 
 
 
/** @pred new_variables_in_term(+ _Variables_,? _Term_, - _OutputVariables_) 
 
Unify  _OutputVariables_ with all variables occurring in  _Term_ that are not in the list  _Variables_.
*/
 
 
/** @pred subsumes(? _Term1_, ? _Term2_) 
 
Succeed if  _Term1_ subsumes  _Term2_.  Variables in term
 _Term1_ are bound so that the two terms become equal.
*/
 
/** @pred subsumes_chk(? _Term1_, ? _Term2_) 
 
Succeed if  _Term1_ subsumes  _Term2_ but does not bind any
variable in  _Term1_.
*/
 
/** @pred term_hash(+ _Term_, + _Depth_, + _Range_, ? _Hash_)
 
Unify  _Hash_ with a positive integer calculated from the structure
of the term.  The range of the positive integer is from `0` to, but
not including,  _Range_. If  _Depth_ is `-1` the whole term
is considered. Otherwise, the term is considered only up to depth
`1`, where the constants and the principal functor have depth
`1`, and an argument of a term with depth  _I_ has depth  _I+1_. 
 
 
*/
/** @pred term_hash(+ _Term_, ? _Hash_) 
 
 
 
If  _Term_ is ground unify  _Hash_ with a positive integer
calculated from the structure of the term. Otherwise the argument
 _Hash_ is left unbound. The range of the positive integer is from
`0` to, but not including, `33554432`.
 
 
*/
/** @pred unifiable(? _Term1_, ? _Term2_, - _Bindings_) 
 
 
 
Succeed if  _Term1_ and  _Term2_ are unifiable with substitution
 _Bindings_.
 
 
 
 
 */
/** @pred variables_within_term(+ _Variables_,? _Term_, - _OutputVariables_) 
 
 
 
Unify  _OutputVariables_ with the subset of the variables  _Variables_ that occurs in  _Term_.
 
 
*/
/** @pred variant(? _Term1_, ? _Term2_) 
 
 
 
Succeed if  _Term1_ and  _Term2_ are variant terms.
 
 
*/
%term_hash(X,Y) :-
%   term_hash(X,-1,16'1000000,Y).
 
subsumes_chk(X,Y) :-
    \+ \+ subsumes(X,Y).
 
 
 
/** @} */