3 * Interface to relations between expressions. */
6 * GiNaC Copyright (C) 1999-2003 Johannes Gutenberg University Mainz, Germany
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
18 * You should have received a copy of the GNU General Public License
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20 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
23 #ifndef __GINAC_RELATIONAL_H__
24 #define __GINAC_RELATIONAL_H__
31 /** This class holds a relation consisting of two expressions and a logical
32 * relation between them. */
33 class relational : public basic
35 GINAC_DECLARE_REGISTERED_CLASS(relational, basic)
50 relational(const ex & lhs, const ex & rhs, operators oper=equal);
52 // functions overriding virtual functions from base classes
54 void print(const print_context & c, unsigned level = 0) const;
55 unsigned precedence(void) const {return 20;}
56 bool info(unsigned inf) const;
57 unsigned nops() const;
59 ex eval(int level=0) const;
62 ex eval_ncmul(const exvector & v) const;
63 bool match_same_type(const basic & other) const;
64 unsigned return_type(void) const;
65 unsigned return_type_tinfo(void) const;
66 unsigned calchash(void) const;
68 // new virtual functions which can be overridden by derived classes
70 virtual ex lhs(void) const;
71 virtual ex rhs(void) const;
73 // non-virtual functions in this class
75 // For conversions to boolean, as would be used in an if conditional,
76 // implicit conversions from bool to int have a large number of
77 // undesirable side effects. The following safe_bool type enables
78 // use of relational objects in conditionals without those side effects
79 struct safe_bool_helper {
83 typedef void (safe_bool_helper::*safe_bool)();
85 safe_bool make_safe_bool(bool) const;
88 operator safe_bool(void) const;
89 safe_bool operator!(void) const;
101 /** Specialization of is_exactly_a<relational>(obj) for relational objects. */
102 template<> inline bool is_exactly_a<relational>(const basic & obj)
104 return obj.tinfo()==TINFO_relational;
107 // inlined functions for efficiency
108 inline relational::safe_bool relational::operator!() const
110 return make_safe_bool(!static_cast<bool>(*this));
115 #endif // ndef __GINAC_RELATIONAL_H__