BALL::Expression Class Reference
[Kernel Predicates]

Expression class. More...

#include <expression.h>

List of all members.

Public Types
Type Definitions
typedef void *(*	CreationMethod )()
	A creation method for predicates.
Public Member Functions
Constructors and Destructor
	Expression ()
	Default Constructor.
	Expression (const Expression &expression)
	Copy Constructor.
	Expression (const String &expression_string) throw (Exception::ParseError)
	Construct an Expression with a string.
virtual	~Expression ()
	Destructor.
Predicates
bool	hasPredicate (const String &name) const
bool	operator== (const Expression &expression) const
	Equality operator.
Accessors
virtual bool	operator() (const Atom &atom) const
	Evaluate the expression of atom.
ExpressionPredicate *	getPredicate (const String &name, const String &args="") const
	Create a new predicate according to the name.
void	registerPredicate (const String &name, CreationMethod creation_method)
	Register a new predicate class.
void	setExpression (const String &expression) throw (Exception::ParseError)
	Set the expression and build a tree for it.
const String &	getExpressionString () const
	Get the expression string.
const ExpressionTree *	getExpressionTree () const
	Get the expression tree.
const StringHashMap < CreationMethod > &	getCreationMethods () const
	Get the creation methods.
Assignment
Expression &	operator= (const Expression &expression)
	Assignment operator.
virtual void	clear ()
	Clear method.
Protected Member Functions
ExpressionTree *	constructExpressionTree_ (const ExpressionParser::SyntaxTree &tree) throw (Exception::ParseError)
void	registerStandardPredicates_ ()
Protected Attributes
StringHashMap< CreationMethod >	create_methods_
ExpressionTree *	expression_tree_
String	expression_string_

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Detailed Description

Expression class.

This class provides a frontend to ExpressionTree.

Expressions may be built from the following modules:

AND & a conjunction

OR & a disjunction

predicate(argument) & a predicate class that is derived from {ExpressionPredicate) and provides operator () (const Atom& atom) const.

Additionally brackets can be used for grouping. At least one bracket pair must exist which encloses the argument of a predicate. Empty arguments are allowed.

See also:

ExpressionTree

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Member Function Documentation

ExpressionPredicate* BALL::Expression::getPredicate	(	const String &	name,
		const String &	args = ""
	)			const

Create a new predicate according to the name.

If the predicate is not known, return 0.

Parameters:

	name	the name of the predicate
	args	the optional argument of the predicate

virtual bool BALL::Expression::operator()

(

const Atom &

atom

)

const [virtual]

Evaluate the expression of atom.

Parameters:

atom