ginac/relational.cpp

   1 /** @file relational.cpp
   2  *
   3  *  Implementation of relations between expressions */
   4
   5 /*
   6  *  GiNaC Copyright (C) 1999-2001 Johannes Gutenberg University Mainz, Germany
   7  *
   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.
  12  *
  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.
  17  *
  18  *  You should have received a copy of the GNU General Public License
  19  *  along with this program; if not, write to the Free Software
  20  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  21  */
  22
  23 #include <iostream>
  24 #include <stdexcept>
  25
  26 #include "relational.h"
  27 #include "numeric.h"
  28 #include "print.h"
  29 #include "archive.h"
  30 #include "utils.h"
  31
  32 namespace GiNaC {
  33
  34 GINAC_IMPLEMENT_REGISTERED_CLASS(relational, basic)
  35
  36 //////////
  37 // default ctor, dtor, copy ctor, assignment operator and helpers
  38 //////////
  39
  40 relational::relational() : basic(TINFO_relational) {}
  41
  42 void relational::copy(const relational & other)
  43 {
  44         basic::copy(other);
  45         lh=other.lh;
  46         rh=other.rh;
  47         o=other.o;
  48 }
  49
  50 DEFAULT_DESTROY(relational)
  51
  52 //////////
  53 // other ctors
  54 //////////
  55
  56 // public
  57
  58 relational::relational(const ex & lhs, const ex & rhs, operators oper) : basic(TINFO_relational), lh(lhs), rh(rhs), o(oper) {}
  59
  60 //////////
  61 // archiving
  62 //////////
  63
  64 relational::relational(const archive_node &n, const lst &sym_lst) : inherited(n, sym_lst)
  65 {
  66         unsigned int opi;
  67         if (!(n.find_unsigned("op", opi)))
  68                 throw (std::runtime_error("unknown relational operator in archive"));
  69         o = (operators)opi;
  70         n.find_ex("lh", lh, sym_lst);
  71         n.find_ex("rh", rh, sym_lst);
  72 }
  73
  74 void relational::archive(archive_node &n) const
  75 {
  76         inherited::archive(n);
  77         n.add_ex("lh", lh);
  78         n.add_ex("rh", rh);
  79         n.add_unsigned("op", o);
  80 }
  81
  82 DEFAULT_UNARCHIVE(relational)
  83
  84 //////////
  85 // functions overriding virtual functions from base classes
  86 //////////
  87
  88 // public
  89
  90 void relational::print(const print_context & c, unsigned level) const
  91 {
  92         if (is_a<print_tree>(c)) {
  93
  94                 inherited::print(c, level);
  95
  96         } else {
  97
  98                 if (precedence() <= level)
  99                         c.s << "(";
 100                 lh.print(c, precedence());
 101                 switch (o) {
 102                 case equal:
 103                         c.s << "==";
 104                         break;
 105                 case not_equal:
 106                         c.s << "!=";
 107                         break;
 108                 case less:
 109                         c.s << "<";
 110                         break;
 111                 case less_or_equal:
 112                         c.s << "<=";
 113                         break;
 114                 case greater:
 115                         c.s << ">";
 116                         break;
 117                 case greater_or_equal:
 118                         c.s << ">=";
 119                         break;
 120                 default:
 121                         c.s << "(INVALID RELATIONAL OPERATOR)";
 122                 }
 123                 rh.print(c, precedence());
 124                 if (precedence() <= level)
 125                         c.s << ")";
 126         }
 127 }
 128
 129 bool relational::info(unsigned inf) const
 130 {
 131         switch (inf) {
 132         case info_flags::relation:
 133                 return 1;
 134         case info_flags::relation_equal:
 135                 return o==equal;
 136         case info_flags::relation_not_equal:
 137                 return o==not_equal;
 138         case info_flags::relation_less:
 139                 return o==less;
 140         case info_flags::relation_less_or_equal:
 141                 return o==less_or_equal;
 142         case info_flags::relation_greater:
 143                 return o==greater;
 144         case info_flags::relation_greater_or_equal:
 145                 return o==greater_or_equal;
 146         }
 147         return 0;
 148 }
 149
 150 unsigned relational::nops() const
 151 {
 152         return 2;
 153 }
 154
 155 ex & relational::let_op(int i)
 156 {
 157         GINAC_ASSERT(i>=0);
 158         GINAC_ASSERT(i<2);
 159
 160         return i==0 ? lh : rh;
 161 }
 162
 163 ex relational::eval(int level) const
 164 {
 165         if (level==1)
 166                 return this->hold();
 167
 168         if (level == -max_recursion_level)
 169                 throw(std::runtime_error("max recursion level reached"));
 170
 171         return (new relational(lh.eval(level-1),rh.eval(level-1),o))->setflag(status_flags::dynallocated | status_flags::evaluated);
 172 }
 173
 174 ex relational::simplify_ncmul(const exvector & v) const
 175 {
 176         return lh.simplify_ncmul(v);
 177 }
 178
 179 // protected
 180
 181 int relational::compare_same_type(const basic & other) const
 182 {
 183         GINAC_ASSERT(is_exactly_a<relational>(other));
 184         const relational &oth = static_cast<const relational &>(other);
 185
 186         if (o == oth.o) {
 187                 int cmpval = lh.compare(oth.lh);
 188                 if (cmpval)
 189                         return cmpval;
 190                 else
 191                         return rh.compare(oth.rh);
 192         }
 193         return (o < oth.o) ? -1 : 1;
 194 }
 195
 196 bool relational::match_same_type(const basic & other) const
 197 {
 198         GINAC_ASSERT(is_exactly_a<relational>(other));
 199         const relational &oth = static_cast<const relational &>(other);
 200
 201         return o == oth.o;
 202 }
 203
 204 unsigned relational::return_type(void) const
 205 {
 206         GINAC_ASSERT(lh.return_type()==rh.return_type());
 207         return lh.return_type();
 208 }
 209
 210 unsigned relational::return_type_tinfo(void) const
 211 {
 212         GINAC_ASSERT(lh.return_type_tinfo()==rh.return_type_tinfo());
 213         return lh.return_type_tinfo();
 214 }
 215
 216 //////////
 217 // new virtual functions which can be overridden by derived classes
 218 //////////
 219
 220 /** Left hand side of relational. */
 221 ex relational::lhs(void) const
 222 {
 223         return lh;
 224 }
 225
 226 /** Right hand side of relational. */
 227 ex relational::rhs(void) const
 228 {
 229         return rh;
 230 }
 231
 232 //////////
 233 // non-virtual functions in this class
 234 //////////
 235
 236 /** Cast the relational into a boolean, mainly for evaluation within an
 237  *  if-statement.  Note that (a<b) == false does not imply (a>=b) == true in
 238  *  the general symbolic case.  A false result means the comparison is either
 239  *  false or undecidable (except of course for !=, where true means either
 240  *  unequal or undecidable). */
 241 relational::operator bool() const
 242 {
 243         const ex df = lh-rh;
 244         if (!is_ex_exactly_of_type(df,numeric))
 245                 // cannot decide on non-numerical results
 246                 return o==not_equal ? true : false;
 247
 248         switch (o) {
 249         case equal:
 250                 return ex_to<numeric>(df).is_zero();
 251         case not_equal:
 252                 return !ex_to<numeric>(df).is_zero();
 253         case less:
 254                 return ex_to<numeric>(df)<_num0;
 255         case less_or_equal:
 256                 return ex_to<numeric>(df)<=_num0;
 257         case greater:
 258                 return ex_to<numeric>(df)>_num0;
 259         case greater_or_equal:
 260                 return ex_to<numeric>(df)>=_num0;
 261         default:
 262                 throw(std::logic_error("invalid relational operator"));
 263         }
 264 }
 265
 266 } // namespace GiNaC