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yap-6.3/library/terms.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: terms.yap *
* Last rev: 5/12/99 *
* mods: *
* comments: Term manipulation operations *
* *
*************************************************************************/
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/** @defgroup Terms Utilities On Terms
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@ingroup library
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@{
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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 not 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 variable_in_term(? _Term_,? _Var_)
Succeed if the second argument _Var_ is a variable and occurs in
term _Term_.
*/
/** @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.
*/
:- module(terms, [
term_hash/2,
term_hash/4,
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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
]).
term_hash(T,H) :-
term_hash(T, -1, 33554432, H).
%term_hash(X,Y) :-
% term_hash(X,-1,16'1000000,Y).
subsumes_chk(X,Y) :-
\+ \+ subsumes(X,Y).