//
// AliRsnExpresion class is used to
// handle operators &|!
// in AliRsnCut
//
// authors: Martin Vala (martin.vala@cern.ch)
//          Alberto Pulvirenti (alberto.pulvirenti@ct.infn.it)
//

#ifndef ALIRSNEXPRESSION_H
#define ALIRSNEXPRESSION_H

#include <TObject.h>

class TObjArray;
#include "AliRsnCutSet.h"
class AliRsnVariableExpression;

class AliRsnExpression : public TObject
{

  public:

    // operators for complex cut expressions
    enum ECutOp {
      kOpAND=1,   // AND '&'
      kOpOR,      // OR '|'
      kOpNOT      // Unary negation '!'
    };

    AliRsnExpression() : fVname(0), fArg1(0), fArg2(0), fOperator(0)  {}
    AliRsnExpression(TString exp);
    virtual    ~AliRsnExpression();
    AliRsnExpression(const AliRsnExpression& exp);
    AliRsnExpression&    operator= (const AliRsnExpression& exp);

    virtual Bool_t     Value(TObjArray & vars);
    virtual TString     Unparse() const;

    void SetCutSet(AliRsnCutSet* const theValue) { fgCutSet = theValue; }
    AliRsnCutSet* GetCutSet() const { return fgCutSet; }


    TString                     fVname;   // Variable name
    static AliRsnCutSet        *fgCutSet; // global cutset

  private:
    AliRsnExpression*           fArg1;         // left argument
    AliRsnExpression*           fArg2;         // right argument
    Int_t                       fOperator;     // operator

    AliRsnExpression(int op, AliRsnExpression* a);
    AliRsnExpression(int op, AliRsnExpression* a, AliRsnExpression* b);

    TObjArray*    Tokenize(TString str) const;
    static AliRsnExpression*    Element(TObjArray &st, Int_t &i);
    static AliRsnExpression*    Primary(TObjArray &st, Int_t &i);
    static AliRsnExpression*    Expression(TObjArray &st, Int_t &i);

    ClassDef(AliRsnExpression, 1);    // Class to evaluate an expression
};

#endif