ginac/relational.cpp

   1 /** @file relational.cpp
   2  *
   3  *  Implementation of relations between expressions */
   4
   5 /*
   6  *  GiNaC Copyright (C) 1999-2004 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 "operators.h"
  28 #include "numeric.h"
  29 #include "archive.h"
  30 #include "utils.h"
  31
  32 namespace GiNaC {
  33
  34 GINAC_IMPLEMENT_REGISTERED_CLASS_OPT(relational, basic,
  35   print_func<print_context>(&relational::do_print).
  36   print_func<print_tree>(&relational::do_print_tree).
  37   print_func<print_python_repr>(&relational::do_print_python_repr))
  38
  39 //////////
  40 // default constructor
  41 //////////
  42
  43 relational::relational() : basic(TINFO_relational) {}
  44
  45 //////////
  46 // other constructors
  47 //////////
  48
  49 // public
  50
  51 relational::relational(const ex & lhs, const ex & rhs, operators oper) : basic(TINFO_relational), lh(lhs), rh(rhs), o(oper) {}
  52
  53 //////////
  54 // archiving
  55 //////////
  56
  57 relational::relational(const archive_node &n, lst &sym_lst) : inherited(n, sym_lst)
  58 {
  59         unsigned int opi;
  60         if (!(n.find_unsigned("op", opi)))
  61                 throw (std::runtime_error("unknown relational operator in archive"));
  62         o = (operators)opi;
  63         n.find_ex("lh", lh, sym_lst);
  64         n.find_ex("rh", rh, sym_lst);
  65 }
  66
  67 void relational::archive(archive_node &n) const
  68 {
  69         inherited::archive(n);
  70         n.add_ex("lh", lh);
  71         n.add_ex("rh", rh);
  72         n.add_unsigned("op", o);
  73 }
  74
  75 DEFAULT_UNARCHIVE(relational)
  76
  77 //////////
  78 // functions overriding virtual functions from base classes
  79 //////////
  80
  81 // public
  82
  83 static void print_operator(const print_context & c, relational::operators o)
  84 {
  85         switch (o) {
  86         case relational::equal:
  87                 c.s << "==";
  88                 break;
  89         case relational::not_equal:
  90                 c.s << "!=";
  91                 break;
  92         case relational::less:
  93                 c.s << "<";
  94                 break;
  95         case relational::less_or_equal:
  96                 c.s << "<=";
  97                 break;
  98         case relational::greater:
  99                 c.s << ">";
 100                 break;
 101         case relational::greater_or_equal:
 102                 c.s << ">=";
 103                 break;
 104         default:
 105                 c.s << "(INVALID RELATIONAL OPERATOR)";
 106                 break;
 107         }
 108 }
 109
 110 void relational::do_print(const print_context & c, unsigned level) const
 111 {
 112         if (precedence() <= level)
 113                 c.s << "(";
 114         lh.print(c, precedence());
 115         print_operator(c, o);
 116         rh.print(c, precedence());
 117         if (precedence() <= level)
 118                 c.s << ")";
 119 }
 120
 121 void relational::do_print_python_repr(const print_python_repr & c, unsigned level) const
 122 {
 123         c.s << class_name() << '(';
 124         lh.print(c);
 125         c.s << ',';
 126         rh.print(c);
 127         c.s << ",'";
 128         print_operator(c, o);
 129         c.s << "')";
 130 }
 131
 132 bool relational::info(unsigned inf) const
 133 {
 134         switch (inf) {
 135                 case info_flags::relation:
 136                         return 1;
 137                 case info_flags::relation_equal:
 138                         return o==equal;
 139                 case info_flags::relation_not_equal:
 140                         return o==not_equal;
 141                 case info_flags::relation_less:
 142                         return o==less;
 143                 case info_flags::relation_less_or_equal:
 144                         return o==less_or_equal;
 145                 case info_flags::relation_greater:
 146                         return o==greater;
 147                 case info_flags::relation_greater_or_equal:
 148                         return o==greater_or_equal;
 149         }
 150         return 0;
 151 }
 152
 153 size_t relational::nops() const
 154 {
 155         return 2;
 156 }
 157
 158 ex relational::op(size_t i) const
 159 {
 160         GINAC_ASSERT(i<2);
 161
 162         return i==0 ? lh : rh;
 163 }
 164
 165 ex relational::map(map_function & f) const
 166 {
 167         return (new relational(f(lh), f(rh), o))->setflag(status_flags::dynallocated);
 168 }
 169
 170 ex relational::eval(int level) const
 171 {
 172         if (level==1)
 173                 return this->hold();
 174
 175         if (level == -max_recursion_level)
 176                 throw(std::runtime_error("max recursion level reached"));
 177
 178         return (new relational(lh.eval(level-1),rh.eval(level-1),o))->setflag(status_flags::dynallocated | status_flags::evaluated);
 179 }
 180
 181 ex relational::subs(const exmap & m, unsigned options) const
 182 {
 183         const ex & subsed_lh = lh.subs(m, options);
 184         const ex & subsed_rh = rh.subs(m, options);
 185
 186         if (!are_ex_trivially_equal(lh, subsed_lh) || !are_ex_trivially_equal(rh, subsed_rh))
 187                 return relational(subsed_lh, subsed_rh, o).subs_one_level(m, options);
 188         else
 189                 return subs_one_level(m, options);
 190 }
 191
 192 ex relational::eval_ncmul(const exvector & v) const
 193 {
 194         return lh.eval_ncmul(v);
 195 }
 196
 197 // protected
 198
 199 int relational::compare_same_type(const basic & other) const
 200 {
 201         GINAC_ASSERT(is_exactly_a<relational>(other));
 202         const relational &oth = static_cast<const relational &>(other);
 203         if (o==oth.o && lh.is_equal(oth.lh) && rh.is_equal(oth.rh))
 204                 return 0;
 205         switch (o) {
 206                 case equal:
 207                 case not_equal:
 208                         if (oth.o!=o)
 209                                 return (o < oth.o) ? -1 : 1;
 210                         break;
 211                 case less:
 212                         if (oth.o!=greater)
 213                                 return (o < oth.o) ? -1 : 1;
 214                         break;
 215                 case less_or_equal:
 216                         if (oth.o!=greater_or_equal)
 217                                 return (o < oth.o) ? -1 : 1;
 218                         break;
 219                 case greater:
 220                         if (oth.o!=less)
 221                                 return (o < oth.o) ? -1 : 1;
 222                         break;
 223                 case greater_or_equal:
 224                         if (oth.o!=less_or_equal)
 225                                 return (o < oth.o) ? -1 : 1;
 226                         break;
 227         }
 228         const int lcmpval = lh.compare(oth.rh);
 229         return (lcmpval!=0) ? lcmpval : rh.compare(oth.lh);
 230 }
 231
 232 bool relational::match_same_type(const basic & other) const
 233 {
 234         GINAC_ASSERT(is_exactly_a<relational>(other));
 235         const relational &oth = static_cast<const relational &>(other);
 236
 237         return o == oth.o;
 238 }
 239
 240 unsigned relational::return_type() const
 241 {
 242         GINAC_ASSERT(lh.return_type()==rh.return_type());
 243         return lh.return_type();
 244 }
 245
 246 unsigned relational::return_type_tinfo() const
 247 {
 248         GINAC_ASSERT(lh.return_type_tinfo()==rh.return_type_tinfo());
 249         return lh.return_type_tinfo();
 250 }
 251
 252 unsigned relational::calchash() const
 253 {
 254         unsigned v = golden_ratio_hash(tinfo());
 255         unsigned lhash = lh.gethash();
 256         unsigned rhash = rh.gethash();
 257
 258         v = rotate_left(v);
 259         switch(o) {
 260                 case equal:
 261                 case not_equal:
 262                         if (lhash>rhash) {
 263                                 v ^= lhash;
 264                                 lhash = rhash;
 265                         } else {
 266                                 v ^= rhash;
 267                         }
 268                         break;
 269                 case less:
 270                 case less_or_equal:
 271                         v ^= rhash;
 272                         break;
 273                 case greater:
 274                 case greater_or_equal:
 275                         v ^= lhash;
 276                         lhash = rhash;
 277                         break;
 278         }
 279         v = rotate_left(v);
 280         v ^= lhash;
 281
 282         // store calculated hash value only if object is already evaluated
 283         if (flags & status_flags::evaluated) {
 284                 setflag(status_flags::hash_calculated);
 285                 hashvalue = v;
 286         }
 287
 288         return v;
 289 }
 290
 291 //////////
 292 // new virtual functions which can be overridden by derived classes
 293 //////////
 294
 295 /** Left hand side of relational. */
 296 ex relational::lhs() const
 297 {
 298         return lh;
 299 }
 300
 301 /** Right hand side of relational. */
 302 ex relational::rhs() const
 303 {
 304         return rh;
 305 }
 306
 307 //////////
 308 // non-virtual functions in this class
 309 //////////
 310
 311 relational::safe_bool relational::make_safe_bool(bool cond) const
 312 {
 313         return cond? &safe_bool_helper::nonnull : 0;
 314 }
 315
 316 /** Cast the relational into a boolean, mainly for evaluation within an
 317  *  if-statement.  Note that (a<b) == false does not imply (a>=b) == true in
 318  *  the general symbolic case.  A false result means the comparison is either
 319  *  false or undecidable (except of course for !=, where true means either
 320  *  unequal or undecidable). */
 321 relational::operator relational::safe_bool() const
 322 {
 323         const ex df = lh-rh;
 324         if (!is_exactly_a<numeric>(df))
 325                 // cannot decide on non-numerical results
 326                 return o==not_equal ? make_safe_bool(true) : make_safe_bool(false);
 327
 328         switch (o) {
 329                 case equal:
 330                         return make_safe_bool(ex_to<numeric>(df).is_zero());
 331                 case not_equal:
 332                         return make_safe_bool(!ex_to<numeric>(df).is_zero());
 333                 case less:
 334                         return make_safe_bool(ex_to<numeric>(df)<_num0);
 335                 case less_or_equal:
 336                         return make_safe_bool(ex_to<numeric>(df)<=_num0);
 337                 case greater:
 338                         return make_safe_bool(ex_to<numeric>(df)>_num0);
 339                 case greater_or_equal:
 340                         return make_safe_bool(ex_to<numeric>(df)>=_num0);
 341                 default:
 342                         throw(std::logic_error("invalid relational operator"));
 343         }
 344 }
 345
 346 } // namespace GiNaC