utils.yap

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 /*************************************************************************
 *                                   *
 *   YAP Prolog                              *
 *                                   *
 *  Yap Prolog was developed at NCCUP - Universidade do Porto    *
 *                                   *
 * Copyright L.Damas, V.S.Costa and Universidade do Porto 1985-1997  *
 *                                   *
 **************************************************************************
 *                                   *
 * File:        utils.yap                        *
 * Last rev:    8/2/88                           *
 * mods:                                     *
 * comments:    Some utility predicates available in yap         *
 *                                   *
 *************************************************************************/
 
/**
  * @file   utils.yap
  * @author VITOR SANTOS COSTA <vsc@VITORs-MBP-2.lan>
  * @date   Thu Oct 19 12:21:01 2017
  * 
  * @brief  Utilities
  *
  * @defgroup MixBag Diverse Utilities
  * @ingroup Builtins
  * 
  * 
  */
 
 
 :-
    .
 
%%% current ....
 
/** @pred  simple( _T_)
 
 
Checks whether  _T_ is unbound, an atom, or a number.
 
 
*/
simple(V) :- var(V), var.
simple(A) :- atom(A), atom.
simple(N) :- number(N).
 
/** @pred  nth_instance(? _Key_,? _Index_,? _R_)
 
 
Fetches the  _Index_nth entry in the internal database under the key
 _Key_. Entries are numbered from one. If the key  _Key_ or the
 _Index_ are bound, a reference is unified with  _R_. Otherwise,
the reference  _R_ must be given, and YAP will find
the matching key and index.
 
 
*/
nth_instance(Key,Index,Ref) :-
    nonvar(Key), var(Index), var(Ref), var,
    recorded(Key,_,Ref),
    '$nth_instance'(_,Index,Ref).
nth_instance(Key,Index,Ref) :-
    '$nth_instance'(Key,Index,Ref).
 
/** @pred  nth_instance(? _Key_,? _Index_, _T_,? _R_)
 
Fetches the  _Index_nth entry in the internal database under the key
 _Key_. Entries are numbered from one. If the key  _Key_ or the
 _Index_ are bound, a reference is unified with  _R_. Otherwise,
the reference  _R_ must be given, and YAP will find
the matching key and index.
 
 
*/
nth_instance(Key,Index,T,Ref) :-
    nonvar(Key), var(Index), var(Ref), var,
    recorded(Key,T,Ref),
    '$nth_instance'(_,Index,Ref).
nth_instance(Key,Index,T,Ref) :-
    '$nth_instance'(Key,Index,Ref),
    instance(Ref,T).
 
/** @pred  nb_current(? _Name_, ? _Value_)
 
 
Enumerate all defined variables with their value. The order of
enumeration is undefined.
 
 
*/
/** @pred nb_current(? _Name_,? _Value_)
 
 
Enumerate all defined variables with their value. The order of
enumeration is undefined.
 
 
*/
nb_current(GlobalVariable, Val) :-
    '$nb_current'(GlobalVariable),
    '__NB_getval__'(GlobalVariable, Val, _).
 
'$getval_exception'(GlobalVariable, _Val, Caller) :-
    '$getval_exception':exception(undefined_global_variable, GlobalVariable, Action),
    exception,
    (
     Action == fail
    ->
     fail
    ;
     Action == retry
    ->
     true
    ;
     Action == error
    ->
     '$do_error'(existence_error(variable, GlobalVariable),Caller)
    ;
     '$do_error'(type_error(atom, Action),Caller)
    ).
 
 
/** @pred  subsumes_term(? _Subsumer_, ? _Subsumed_)
 
 
 
Succeed if  _Submuser_ subsumes  _Subsuned_ but does not bind any
variable in  _Subsumer_.
 
 
*/
subsumes_term(A,B) :-
    \+ \+ subsumes_term:subsumes(A,B).
 
term_string( T, S, Opts) :-
    var( T ),
    var,
    var:open_mem_read_stream( S, Stream ),
    read_term( Stream, T, Opts ),
    close( Stream ).
    term_string( T, S, _Opts) :-
        format(string(S), '~q.~n', [T]).
 
 
term_hash(T,H) :-
    term_hash:term_hash(T, -1, 33554432, H).
/*
numbervars( T, I0, I) :-
    term_variables(T, Vs),
    bind_variables(Vs,I0,I).
 
bind_variables([],I,I).
bind_variables(['$VAR'(I0)|Vs],I0,I) :-
    I1 is I0+1,
    bind_variables(Vs,I1,I).
*/