ginac/relational.cpp

   1 /** @file relational.cpp
   2  *
   3  *  Implementation of relations between expressions */
   4
   5 /*
   6  *  GiNaC Copyright (C) 1999-2003 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 "print.h"
  30 #include "archive.h"
  31 #include "utils.h"
  32
  33 namespace GiNaC {
  34
  35 GINAC_IMPLEMENT_REGISTERED_CLASS(relational, basic)
  36
  37 //////////
  38 // default ctor, dtor, copy ctor, assignment operator and helpers
  39 //////////
  40
  41 relational::relational() : basic(TINFO_relational) {}
  42
  43 void relational::copy(const relational & other)
  44 {
  45         basic::copy(other);
  46         lh=other.lh;
  47         rh=other.rh;
  48         o=other.o;
  49 }
  50
  51 DEFAULT_DESTROY(relational)
  52
  53 //////////
  54 // other ctors
  55 //////////
  56
  57 // public
  58
  59 relational::relational(const ex & lhs, const ex & rhs, operators oper) : basic(TINFO_relational), lh(lhs), rh(rhs), o(oper) {}
  60
  61 //////////
  62 // archiving
  63 //////////
  64
  65 relational::relational(const archive_node &n, const lst &sym_lst) : inherited(n, sym_lst)
  66 {
  67         unsigned int opi;
  68         if (!(n.find_unsigned("op", opi)))
  69                 throw (std::runtime_error("unknown relational operator in archive"));
  70         o = (operators)opi;
  71         n.find_ex("lh", lh, sym_lst);
  72         n.find_ex("rh", rh, sym_lst);
  73 }
  74
  75 void relational::archive(archive_node &n) const
  76 {
  77         inherited::archive(n);
  78         n.add_ex("lh", lh);
  79         n.add_ex("rh", rh);
  80         n.add_unsigned("op", o);
  81 }
  82
  83 DEFAULT_UNARCHIVE(relational)
  84
  85 //////////
  86 // functions overriding virtual functions from base classes
  87 //////////
  88
  89 // public
  90
  91 void relational::print(const print_context & c, unsigned level) const
  92 {
  93         if (is_a<print_tree>(c)) {
  94
  95                 inherited::print(c, level);
  96
  97         } else {
  98
  99                 if (is_a<print_python_repr>(c)) {
 100                         c.s << class_name() << '(';
 101                         lh.print(c);
 102                         c.s << ',';
 103                         rh.print(c);
 104                         c.s << ",'";
 105                 } else {
 106                         if (precedence() <= level)
 107                                 c.s << "(";
 108                         lh.print(c, precedence());
 109                 }
 110                 switch (o) {
 111                         case equal:
 112                                 c.s << "==";
 113                                 break;
 114                         case not_equal:
 115                                 c.s << "!=";
 116                                 break;
 117                         case less:
 118                                 c.s << "<";
 119                                 break;
 120                         case less_or_equal:
 121                                 c.s << "<=";
 122                                 break;
 123                         case greater:
 124                                 c.s << ">";
 125                                 break;
 126                         case greater_or_equal:
 127                                 c.s << ">=";
 128                                 break;
 129                         default:
 130                                 c.s << "(INVALID RELATIONAL OPERATOR)";
 131                 }
 132                 if (is_a<print_python_repr>(c))
 133                         c.s << "')";
 134                 else {
 135                         rh.print(c, precedence());
 136                         if (precedence() <= level)
 137                                 c.s << ")";
 138                 }
 139         }
 140 }
 141
 142 bool relational::info(unsigned inf) const
 143 {
 144         switch (inf) {
 145                 case info_flags::relation:
 146                         return 1;
 147                 case info_flags::relation_equal:
 148                         return o==equal;
 149                 case info_flags::relation_not_equal:
 150                         return o==not_equal;
 151                 case info_flags::relation_less:
 152                         return o==less;
 153                 case info_flags::relation_less_or_equal:
 154                         return o==less_or_equal;
 155                 case info_flags::relation_greater:
 156                         return o==greater;
 157                 case info_flags::relation_greater_or_equal:
 158                         return o==greater_or_equal;
 159         }
 160         return 0;
 161 }
 162
 163 unsigned relational::nops() const
 164 {
 165         return 2;
 166 }
 167
 168 ex & relational::let_op(int i)
 169 {
 170         GINAC_ASSERT(i>=0);
 171         GINAC_ASSERT(i<2);
 172
 173         return i==0 ? lh : rh;
 174 }
 175
 176 ex relational::eval(int level) const
 177 {
 178         if (level==1)
 179                 return this->hold();
 180
 181         if (level == -max_recursion_level)
 182                 throw(std::runtime_error("max recursion level reached"));
 183
 184         return (new relational(lh.eval(level-1),rh.eval(level-1),o))->setflag(status_flags::dynallocated | status_flags::evaluated);
 185 }
 186
 187 ex relational::eval_ncmul(const exvector & v) const
 188 {
 189         return lh.eval_ncmul(v);
 190 }
 191
 192 // protected
 193
 194 int relational::compare_same_type(const basic & other) const
 195 {
 196         GINAC_ASSERT(is_exactly_a<relational>(other));
 197         const relational &oth = static_cast<const relational &>(other);
 198         if (o==oth.o && lh.is_equal(oth.lh) && rh.is_equal(oth.rh))
 199                 return 0;
 200         switch (o) {
 201                 case equal:
 202                 case not_equal:
 203                         if (oth.o!=o)
 204                                 return (o < oth.o) ? -1 : 1;
 205                         break;
 206                 case less:
 207                         if (oth.o!=greater)
 208                                 return (o < oth.o) ? -1 : 1;
 209                         break;
 210                 case less_or_equal:
 211                         if (oth.o!=greater_or_equal)
 212                                 return (o < oth.o) ? -1 : 1;
 213                         break;
 214                 case greater:
 215                         if (oth.o!=less)
 216                                 return (o < oth.o) ? -1 : 1;
 217                         break;
 218                 case greater_or_equal:
 219                         if (oth.o!=less_or_equal)
 220                                 return (o < oth.o) ? -1 : 1;
 221                         break;
 222         }
 223         const int lcmpval = lh.compare(oth.rh);
 224         return (lcmpval!=0) ? lcmpval : rh.compare(oth.lh);
 225 }
 226
 227 bool relational::match_same_type(const basic & other) const
 228 {
 229         GINAC_ASSERT(is_exactly_a<relational>(other));
 230         const relational &oth = static_cast<const relational &>(other);
 231
 232         return o == oth.o;
 233 }
 234
 235 unsigned relational::return_type(void) const
 236 {
 237         GINAC_ASSERT(lh.return_type()==rh.return_type());
 238         return lh.return_type();
 239 }
 240
 241 unsigned relational::return_type_tinfo(void) const
 242 {
 243         GINAC_ASSERT(lh.return_type_tinfo()==rh.return_type_tinfo());
 244         return lh.return_type_tinfo();
 245 }
 246
 247 unsigned relational::calchash(void) const
 248 {
 249         unsigned v = golden_ratio_hash(tinfo());
 250         unsigned lhash = lh.gethash();
 251         unsigned rhash = rh.gethash();
 252
 253         v = rotate_left(v);
 254         switch(o) {
 255                 case equal:
 256                 case not_equal:
 257                         if (lhash>rhash) {
 258                                 v ^= lhash;
 259                                 lhash = rhash;
 260                         } else {
 261                                 v ^= rhash;
 262                         }
 263                         break;
 264                 case less:
 265                 case less_or_equal:
 266                         v ^= rhash;
 267                         break;
 268                 case greater:
 269                 case greater_or_equal:
 270                         v ^= lhash;
 271                         lhash = rhash;
 272                         break;
 273         }
 274         v = rotate_left(v);
 275         v ^= lhash;
 276
 277         // store calculated hash value only if object is already evaluated
 278         if (flags & status_flags::evaluated) {
 279                 setflag(status_flags::hash_calculated);
 280                 hashvalue = v;
 281         }
 282
 283         return v;
 284 }
 285
 286 //////////
 287 // new virtual functions which can be overridden by derived classes
 288 //////////
 289
 290 /** Left hand side of relational. */
 291 ex relational::lhs(void) const
 292 {
 293         return lh;
 294 }
 295
 296 /** Right hand side of relational. */
 297 ex relational::rhs(void) const
 298 {
 299         return rh;
 300 }
 301
 302 //////////
 303 // non-virtual functions in this class
 304 //////////
 305
 306 relational::safe_bool relational::make_safe_bool(bool cond) const
 307 {
 308         return cond? &safe_bool_helper::nonnull : 0;
 309 }
 310
 311 /** Cast the relational into a boolean, mainly for evaluation within an
 312  *  if-statement.  Note that (a<b) == false does not imply (a>=b) == true in
 313  *  the general symbolic case.  A false result means the comparison is either
 314  *  false or undecidable (except of course for !=, where true means either
 315  *  unequal or undecidable). */
 316 relational::operator relational::safe_bool() const
 317 {
 318         const ex df = lh-rh;
 319         if (!is_exactly_a<numeric>(df))
 320                 // cannot decide on non-numerical results
 321                 return o==not_equal ? make_safe_bool(true) : make_safe_bool(false);
 322
 323         switch (o) {
 324                 case equal:
 325                         return make_safe_bool(ex_to<numeric>(df).is_zero());
 326                 case not_equal:
 327                         return make_safe_bool(!ex_to<numeric>(df).is_zero());
 328                 case less:
 329                         return make_safe_bool(ex_to<numeric>(df)<_num0);
 330                 case less_or_equal:
 331                         return make_safe_bool(ex_to<numeric>(df)<=_num0);
 332                 case greater:
 333                         return make_safe_bool(ex_to<numeric>(df)>_num0);
 334                 case greater_or_equal:
 335                         return make_safe_bool(ex_to<numeric>(df)>=_num0);
 336                 default:
 337                         throw(std::logic_error("invalid relational operator"));
 338         }
 339 }
 340
 341 } // namespace GiNaC