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/**
@defgroup YAPControl Control Predicates
@ingroup YAPBuiltins
@{
*/
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/** @pred + _P_ is nondet
The same as `call( _P_)`. This feature has been kept to provide
compatibility with C-Prolog. When compiling a goal, YAP
generates a `call( _X_)` whenever a variable _X_ is found as
a goal.
~~~~~{.prolog}
a(X) :- X.
~~~~~
is converted to:
~~~~~{.prolog}
a(X) :- call(X).
~~~~~
*/
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/** @pred _CurrentModule_:term_expansion( _T_,- _X_), user:term_expansion( _T_,- _X_)
This user-defined predicate is called by `expand_term/3` to
preprocess all terms read when consulting a file. If it succeeds:
+
If _X_ is of the form `:- G` or `?- G`, it is processed as
a directive.
+
If _X_ is of the form `$source_location`( _File_, _Line_): _Clause_` it is processed as if from `File` and line `Line`.
+
If _X_ is a list, all terms of the list are asserted or processed
as directives.
+ The term _X_ is asserted instead of _T_.
*/
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/** @pred _CurrentModule_:goal_expansion(+ _G_,+ _M_,- _NG_), user:goal_expansion(+ _G_,+ _M_,- _NG_)
YAP now supports goal_expansion/3. This is an user-defined
procedure that is called after term expansion when compiling or
asserting goals for each sub-goal in a clause. The first argument is
bound to the goal and the second to the module under which the goal
_G_ will execute. If goal_expansion/3 succeeds the new
sub-goal _NG_ will replace _G_ and will be processed in the same
way. If goal_expansion/3 fails the system will use the default
rules.
*/
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/** @pred `C`( _S1_, _T_, _S2_)
This predicate is used by the grammar rules compiler and is defined as
`C`([H|T],H,T)`.
*/
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/** @pred initialization
Execute the goals defined by initialization/1. Only the first answer is
considered.
*/
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/** @pred [nondet]aggregate(+ _Template_, + _Discriminator_, : _Goal_, - _Result_)
Aggregate bindings in _Goal_ according to _Template_. The
aggregate/3 version performs setof/3 on _Goal_.
*/
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/** @pred _X_ #= is det
all elements of _X_ must take the same value
*/
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/** @pred _X_ #\= is det
not all elements of _X_ take the same value
*/
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/** @pred _X_ #> is det
elements of _X_ must be increasing
*/
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/** @pred _X_ #>= is det
elements of _X_ must be increasinga or equal
*/
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/** @pred _X_ #=< is det
elements of _X_ must be decreasing
*/
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/** @pred _X_ #< is det
elements of _X_ must be decreasing or equal
*/
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/** @pred :- fragile _P_,....,_Pn_ is directive
Declares the predicate _P_=[module:]name/arity as a fragile
predicate, module is optional, default is the current
typein_module. Whenever such a fragile predicate is used in a query
it will be called through call_cleanup/1.
~~~~~{.prolog}
:- fragile foo/1,bar:baz/2.
~~~~~
*/
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/** @pred undgraph_vertices(+ _Graph_, - _Vertices_)
Unify _Vertices_ with all vertices appearing in graph
_Graph_.
*/
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/** @pred undgraph_edge(+ _N1_, + _N2_, + _Graph_)
Edge _N1_- _N2_ is an edge in undirected graph _Graph_.
*/
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/** @pred undgraph_complement(+ _Graph_, - _NewGraph_)
Unify _NewGraph_ with the graph complementary to _Graph_.
*/
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/** @pred dgraph_to_undgraph( + _DGraph_, - _UndGraph_)
Unify _UndGraph_ with the undirected graph obtained from the
directed graph _DGraph_.
*/
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/** @pred _Module_:get_atts( _-Var_, _?ListOfAttributes_)
Unify the list _?ListOfAttributes_ with the attributes for the unbound
variable _Var_. Each member of the list must be a bound term of the
form `+( _Attribute_)`, `-( _Attribute_)` (the kbd
prefix may be dropped). The meaning of + and - is:
+ +( _Attribute_)
Unifies _Attribute_ with a corresponding attribute associated with
_Var_, fails otherwise.
+ -( _Attribute_)
Succeeds if a corresponding attribute is not associated with
_Var_. The arguments of _Attribute_ are ignored.
*/
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/** @pred _Module_:put_atts( _-Var_, _?ListOfAttributes_)
Associate with or remove attributes from a variable _Var_. The
attributes are given in _?ListOfAttributes_, and the action depends
on how they are prefixed:
+ +( _Attribute_)
Associate _Var_ with _Attribute_. A previous value for the
attribute is simply replace (like with `set_mutable/2`).
+ -( _Attribute_)
Remove the attribute with the same name. If no such attribute existed,
simply succeed.
*/
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/** @pred _Module_:verify_attributes( _-Var_, _+Value_, _-Goals_)
The predicate is called when trying to unify the attributed variable
_Var_ with the Prolog term _Value_. Note that _Value_ may be
itself an attributed variable, or may contain attributed variables. The
goal verify_attributes/3 is actually called before _Var_ is
unified with _Value_.
It is up to the user to define which actions may be performed by
verify_attributes/3 but the procedure is expected to return in
_Goals_ a list of goals to be called after _Var_ is
unified with _Value_. If verify_attributes/3 fails, the
unification will fail.
Notice that the verify_attributes/3 may be called even if _Var_<
has no attributes in module Module. In this case the routine should
simply succeed with _Goals_ unified with the empty list.
*/
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/** @pred _Module_:attribute_goal( _-Var_, _-Goal_)
User-defined procedure, called to convert the attributes in _Var_ to
a _Goal_. Should fail when no interpretation is available.
*/
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/** @pred _Module_:project_attributes( _+QueryVars_, _+AttrVars_)
Given a list of variables _QueryVars_ and list of attributed
variables _AttrVars_, project all attributes in _AttrVars_ to
_QueryVars_. Although projection is constraint system dependent,
typically this will involve expressing all constraints in terms of
_QueryVars_ and considering all remaining variables as existentially
quantified.
Projection interacts with attribute_goal/2 at the Prolog top
level. When the query succeeds, the system first calls
project_attributes/2. The system then calls
attribute_goal/2 to get a user-level representation of the
constraints. Typically, attribute_goal/2 will convert from the
original constraints into a set of new constraints on the projection,
and these constraints are the ones that will have an
attribute_goal/2 handler.
*/
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/** @pred {+ _Constraints_} is det
Adds the constraints given by _Constraints_ to the constraint store.
*/