1 /*****************************************************************************
2  * expr_evaluator.hpp
3  *****************************************************************************
4  * Copyright (C) 2004 the VideoLAN team
5  * $Id: 7bf2a0d313b7e645e475cb3338c2b4489af9a262 $
6  *
7  * Authors: Cyril Deguet     <asmax@via.ecp.fr>
8  *
9  * This program is free software; you can redistribute it and/or modify
10  * it under the terms of the GNU General Public License as published by
11  * the Free Software Foundation; either version 2 of the License, or
12  * (at your option) any later version.
13  *
14  * This program is distributed in the hope that it will be useful,
15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
17  * GNU General Public License for more details.
18  *
19  * You should have received a copy of the GNU General Public License along
20  * with this program; if not, write to the Free Software Foundation, Inc.,
21  * 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
22  *****************************************************************************/
23 
24 #ifndef EXPR_EVALUATOR_HPP
25 #define EXPR_EVALUATOR_HPP
26 
27 #include "../src/skin_common.hpp"
28 #include <list>
29 #include <string>
30 
31 /// Expression evaluator using Reverse Polish Notation
32 class ExprEvaluator: public SkinObject
33 {
34 public:
ExprEvaluator(intf_thread_t * pIntf)35     ExprEvaluator( intf_thread_t *pIntf ): SkinObject( pIntf ) { }
~ExprEvaluator()36     ~ExprEvaluator() { }
37 
38     /// Clear the RPN stack and parse an expression
39     void parse( const std::string &rExpr );
40 
41     /// Pop the first token from the RPN stack.
42     /// Return NULL when the stack is empty.
43     std::string getToken();
44 
45 private:
46     /// RPN stack
47     std::list<std::string> m_stack;
48 
49     /// Returns true if op1 has precedency over op2
50     bool hasPrecedency( const std::string &op1, const std::string &op2 ) const;
51 };
52 
53 #endif
54