pl_search::IfThenElse Class Reference

Represents the equivalent of Prolog if-then-else i.e. (G1 -> G2; G3) - similar to (G1, !, G2; G3) More...

#include <pred.hpp>

Inheritance diagram for pl_search::IfThenElse:

Collaboration diagram for pl_search::IfThenElse:

Public Member Functions
	IfThenElse (Trail *trail, PredPtr if_pred, PredPtr then_pred, PredPtr else_pred)
	The equlvalent of the Prolog call (If -> Then ; Else)
void	set_continuation (PredPtr cont) override
	Sets the continuation for the then and else predicates to the given continuation which will be the continuation of the IfThenElse predicate.
bool	call () override
Public Member Functions inherited from pl_search::Pred
	Pred (Trail *trail)
	Default constructor.
PredPtr	get_continuation ()
	Gets the continuation of the predicate.
PredPtr	last_pred ()
	Follows the continuation chain to the last predicate.
bool	call_continuation ()
	Calls the continuation of the predicate.
virtual	~Pred ()=default
	Virtual destructor for proper cleanup.
virtual std::string	get_name ()
	For debugging.

Protected Attributes
PredPtr	if_pred
PredPtr	then_pred
PredPtr	else_pred
Protected Attributes inherited from pl_search::Pred
PredPtr	continuation
	The continuation of the predicate.
Trail *	trail
	Pointer to the trail for managing variable bindings.

Detailed Description

Represents the equivalent of Prolog if-then-else i.e. (G1 -> G2; G3) - similar to (G1, !, G2; G3)

The IfThenElse meta-predicate is used to implement the equivalent of Prolog's if-then-else construct. If the guard predicate G1 succeeds then the then predicate G2 is called and any variable bindings made by G1 are preserved but any choice points made by G1 are removed. If G2 or the continuation fails then the IfThenElse predicate fails and any variable bindings made by G1 and G2 are undone. If G1 fails then the else predicate G3 is called and any variable bindings made by G1 are undone. If G3 or the continuation fails then the IfThenElse predicate fails. Note that G1 is a local call - i.e. its continuation is not related to the continuation of the IfThenElse predicate. Also note that the continuations of G2 and G3 are set to the continuation of the IfThenElse predicate. )

Constructor & Destructor Documentation

IfThenElse()

pl_search::IfThenElse::IfThenElse	(	Trail *	eng,
		PredPtr	if_pred,
		PredPtr	then_pred,
		PredPtr	else_pred
	)

The equlvalent of the Prolog call (If -> Then ; Else)

Parameters

trail	Pointer to the trail
if_pred	The guard predicate
then_pred	The then predicate
else_pred	The else predicate
eng	Pointer to the trail
if_pred	The guard predicate
then_pred	The then predicate
else_pred	The else predicate

Member Function Documentation

call()

bool pl_search::IfThenElse::call ( )

overridevirtual

Reimplemented from pl_search::Pred.

set_continuation()

void pl_search::IfThenElse::set_continuation ( PredPtr  cont )

overridevirtual

Sets the continuation for the then and else predicates to the given continuation which will be the continuation of the IfThenElse predicate.

Parameters

cont	A shared pointer to the continuation predicate.

As with DisjPred the continuations of the then and else predicates are set to the continuation of the IfThenElse predicate.

Reimplemented from pl_search::Pred.

Member Data Documentation

else_pred

PredPtr pl_search::IfThenElse::else_pred

protected

if_pred

PredPtr pl_search::IfThenElse::if_pred

protected

then_pred

PredPtr pl_search::IfThenElse::then_pred

protected

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The documentation for this class was generated from the following files:

• include/pl_search/pred.hpp
• src/pred.cpp