File indexing completed on 2024-05-19 04:56:01

 /**
  * \file expressionparser.h
  * Simple parser for expressions.
  *
  * \b Project: Kid3
  * \author Urs Fleisch
  * \date 23 Jan 2008
  *
  * Copyright (C) 2008-2018  Urs Fleisch
  *
  * This file is part of Kid3.
  *
  * Kid3 is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
  * Kid3 is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 #pragma once
 
 #include <QString>
 #include <QStringList>
 
 /**
  * Simple parser for expressions with boolean not, and, or and
  * other binary operations.
  */
 class ExpressionParser {
 public:
   /**
    * Constructor.
    *
    * @param operators additional operators (besides not, and, or),
    *                  highest priority first
    */
   explicit ExpressionParser(QStringList operators);
 
   /**
    * Destructor.
    */
   ~ExpressionParser() = default;
 
   /**
    * Tokenize an expression in reverse polish notation.
    *
    * @param expr with strings, operators, not, and, or, (, ).
    */
   void tokenizeRpn(const QString& expr);
 
   /**
    * Clear the variable stack before restarting an evaluation.
    */
   void clearEvaluation();
 
   /**
    * Evaluate the RPN stack.
    * Boolean operations and, or, not are performed automatically. If another
    * operation has to be performed, the method stops and returns operator
    * and variables. The result can then be pushed onto the stack using
    * pushBool() and then the method can be called again.
    *
    * @param op the operator is returned here
    * @param var1 the first variable is returned here
    * @param var2 the second variable is returned here
    *
    * @return true if the RPN stack has more to evaluate,
    *         if false, the evaluation is finished.
    */
   bool evaluate(QString& op, QString& var1, QString& var2);
 
   /**
    * Push a boolean to the variable stack.
    * Can be used to push the result of the operation returned by
    * evaluate() back onto the variable stack.
    *
    * @param var boolean to  push
    */
   void pushBool(bool var);
 
   /**
    * Check if an error occurred.
    * @return true if an error occurred.
    */
   bool hasError() const { return m_error; }
 
   /**
    * Pop a boolean from the variable stack.
    * Can be used to get the result after evaluate() returns false and
    * no error occurred.
    *
    * @param var the boolean is returned here
    *
    * @return true if ok.
    */
   bool popBool(bool& var);
 
 private:
   /**
    * Compare operator priority.
    *
    * @return true if op1 has less priority than op2.
    */
   bool lessPriority(const QString& op1, const QString& op2) const;
 
   /**
    * Pop two booleans from the variable stack.
    *
    * @param var1 first boolean
    * @param var2 second boolean
    *
    * @return true if ok.
    */
   bool popTwoBools(bool& var1, bool& var2);
 
   QStringList m_rpnStack;
   QStringList m_varStack;
   const QStringList m_operators;
   QStringList::const_iterator m_rpnIterator;
   bool m_error;
 };