expr.h

00001 /* expr.h -- Expression Tree
00002 Copyright 2003 Free Software Foundation, Inc.
00003 Written by Stephane Carrez (stcarrez@nerim.fr)
00004 
00005 This file is part of GEL.
00006 
00007 GEL is free software; you can redistribute it and/or modify
00008 it under the terms of the GNU General Public License as published by
00009 the Free Software Foundation; either version 2, or (at your option)
00010 any later version.
00011 
00012 GEL is distributed in the hope that it will be useful,
00013 but WITHOUT ANY WARRANTY; without even the implied warranty of
00014 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
00015 GNU General Public License for more details.
00016 
00017 You should have received a copy of the GNU General Public License
00018 along with GEL; see the file COPYING. If not, write to
00019 the Free Software Foundation, 59 Temple Place - Suite 330,
00020 Boston, MA 02111-1307, USA. */
00021 
00022 #ifndef _GEL_INTERPRETOR_EXPR_H
00023 #define _GEL_INTERPRETOR_EXPR_H
00024 
00025 #include "config.h"
00026 
00027 #undef far
00028 #undef bank
00029 
00030 // Expression Tree implementation is put in memory bank1.
00031 // - The 'bank' attribute is used on all methods
00032 // - The 'far' attribute is only used on public entry points.
00033 #define bank SECT_ATTR(".text.bank1")
00034 #define far FAR_ATTR(".text.bank1")
00035 
00036 class Variable;
00037 typedef long Value;
00038 
00042 class Expression {
00043 protected:
00044 enum token
00045 {
00046 T_NAME,
00047 T_DIGIT,
00048 T_MINUS,
00049 T_PLUS,
00050 T_AND,
00051 T_OR,
00052 T_XOR,
00053 T_MUL,
00054 T_DIV,
00055 T_NOT,
00056 T_PARENT_OPEN,
00057 T_PARENT_CLOSE,
00058 T_UNKNOWN,
00059 T_EOF
00060 };
00061 enum token type_;
00062 
00063 static bank enum token get_token (const char*& line);
00064 static bank void rewind (enum token t, const char*& line);
00065 
00066 static bank Expression* parse_unary (const char*& line);
00067 static bank Expression* parse_binary (const char*& line, unsigned char prio);
00068 static bank Expression* parse_term (const char*& line);
00069 static bank int get_value(const char*& line, Value& value);
00070 static bank unsigned char get_priority(enum token t);
00071 
00072 virtual far Value eval();
00073 
00074 public:
00075 Expression(enum token t) {
00076 type_ = t;
00077 }
00078 virtual ~Expression();
00079 
00080 far Value evaluate();
00081 
00082 static far Expression* parse(const char*& line);
00083 };
00084 
00086 class BinaryExpression : public Expression {
00087 protected:
00088 Expression* left_;
00089 Expression* right_;
00090 
00091 virtual far Value eval();
00092 
00093 virtual ~BinaryExpression()
00094 {
00095 delete left_;
00096 delete right_;
00097 }
00098 
00099 public:
00100 BinaryExpression(enum token t, Expression* l, Expression* r)
00101 : Expression(t), left_(l), right_(r)
00102 {
00103 }
00104 };
00105 
00107 class UnaryExpression : public Expression {
00108 protected:
00109 Expression* expr_;
00110 
00111 virtual far Value eval();
00112 
00113 virtual ~UnaryExpression()
00114 {
00115 delete expr_;
00116 }
00117 
00118 public:
00119 UnaryExpression(enum token t, Expression* l)
00120 : Expression(t), expr_(l)
00121 {
00122 }
00123 };
00124 
00126 class ValueExpression : public Expression {
00127 long value_;
00128 
00129 virtual far Value eval();
00130 public:
00131 ValueExpression(long value) : Expression(T_DIGIT) 
00132 {
00133 value_ = value;
00134 }
00135 };
00136 
00137 #endif