expression.h

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// -*- Mode: C++; tab-width: 2; -*-
// vi: set ts=2:
//

#ifndef BALL_KERNEL_EXPRESSION_H
#define BALL_KERNEL_EXPRESSION_H

#ifndef BALL_DATATYPE_STRINGHASHMAP_H
# include <BALL/DATATYPE/stringHashMap.h>
#endif

#ifndef BALL_KERNEL_EXPRESSIONPARSER_H
# include <BALL/KERNEL/expressionParser.h>
#endif

namespace BALL
{
  class Atom;
  class ExpressionTree;

  class BALL_EXPORT Expression
  {
    public:

    BALL_CREATE(Expression)

    

    typedef void * (*CreationMethod) ();



    Expression();

    Expression(const Expression& expression);

    Expression(const String& expression_string);

    virtual ~Expression();



    bool hasPredicate(const String& name) const;

    bool operator == (const Expression& expression) const;



    virtual bool operator () (const Atom& atom) const;

    ExpressionPredicate* getPredicate(const String& name,
                                      const String& args = "") const;

    void registerPredicate(const String& name, CreationMethod creation_method);

    void setExpression(const String& expression);

    const String& getExpressionString() const;

    const ExpressionTree* getExpressionTree() const;

    const StringHashMap<CreationMethod>& getCreationMethods() const;



    Expression& operator = (const Expression& expression);

    virtual void clear();


    protected:

    /*_ @name Protected methods
    */

    /*_ Construct the expression tree from the SyntaxTree
     *  @throw Exception::ParseError if a syntax error was encountered
     */
    ExpressionTree* constructExpressionTree_(const ExpressionParser::SyntaxTree& tree);

    /*_ Register the predicates defined by default.
        See also: BALL/KERNEL/standardPredicates.h
    */
    void registerStandardPredicates_();

    /*_ @name Protected attributes
    */

    /*_ The methods to create the ExpressionPredicate instances
    */
    StringHashMap<CreationMethod> create_methods_;

    /*_ The ExpressionTree constructed from the string.
        This tree contains the instances of the predicates.
    */
    ExpressionTree*               expression_tree_;

    /*_ The string describing the expression.
    */
    String                        expression_string_;

  };
}

#endif // BALL_KERNEL_EXPRESSION_H

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