ginac/relational.cpp

   1 /** @file relational.cpp
   2  *
   3  *  Implementation of relations between expressions */
   4
   5 /*
   6  *  GiNaC Copyright (C) 1999-2008 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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  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() { }
  44
  45 //////////
  46 // other constructors
  47 //////////
  48
  49 // public
  50
  51 relational::relational(const ex & lhs, const ex & rhs, operators oper) :
  52         lh(lhs), rh(rhs), o(oper) { }
  53
  54 //////////
  55 // archiving
  56 //////////
  57
  58 void relational::read_archive(const archive_node& n, lst& sym_lst)
  59 {
  60         inherited::read_archive(n, sym_lst);
  61         unsigned int opi;
  62         if (!(n.find_unsigned("op", opi)))
  63                 throw (std::runtime_error("unknown relational operator in archive"));
  64         o = (operators)opi;
  65         n.find_ex("lh", lh, sym_lst);
  66         n.find_ex("rh", rh, sym_lst);
  67 }
  68 GINAC_BIND_UNARCHIVER(relational);
  69
  70 void relational::archive(archive_node &n) const
  71 {
  72         inherited::archive(n);
  73         n.add_ex("lh", lh);
  74         n.add_ex("rh", rh);
  75         n.add_unsigned("op", o);
  76 }
  77
  78 //////////
  79 // functions overriding virtual functions from base classes
  80 //////////
  81
  82 // public
  83
  84 static void print_operator(const print_context & c, relational::operators o)
  85 {
  86         switch (o) {
  87         case relational::equal:
  88                 c.s << "==";
  89                 break;
  90         case relational::not_equal:
  91                 c.s << "!=";
  92                 break;
  93         case relational::less:
  94                 c.s << "<";
  95                 break;
  96         case relational::less_or_equal:
  97                 c.s << "<=";
  98                 break;
  99         case relational::greater:
 100                 c.s << ">";
 101                 break;
 102         case relational::greater_or_equal:
 103                 c.s << ">=";
 104                 break;
 105         default:
 106                 c.s << "(INVALID RELATIONAL OPERATOR)";
 107                 break;
 108         }
 109 }
 110
 111 void relational::do_print(const print_context & c, unsigned level) const
 112 {
 113         if (precedence() <= level)
 114                 c.s << "(";
 115         lh.print(c, precedence());
 116         print_operator(c, o);
 117         rh.print(c, precedence());
 118         if (precedence() <= level)
 119                 c.s << ")";
 120 }
 121
 122 void relational::do_print_python_repr(const print_python_repr & c, unsigned level) const
 123 {
 124         c.s << class_name() << '(';
 125         lh.print(c);
 126         c.s << ',';
 127         rh.print(c);
 128         c.s << ",'";
 129         print_operator(c, o);
 130         c.s << "')";
 131 }
 132
 133 bool relational::info(unsigned inf) const
 134 {
 135         switch (inf) {
 136                 case info_flags::relation:
 137                         return 1;
 138                 case info_flags::relation_equal:
 139                         return o==equal;
 140                 case info_flags::relation_not_equal:
 141                         return o==not_equal;
 142                 case info_flags::relation_less:
 143                         return o==less;
 144                 case info_flags::relation_less_or_equal:
 145                         return o==less_or_equal;
 146                 case info_flags::relation_greater:
 147                         return o==greater;
 148                 case info_flags::relation_greater_or_equal:
 149                         return o==greater_or_equal;
 150         }
 151         return 0;
 152 }
 153
 154 size_t relational::nops() const
 155 {
 156         return 2;
 157 }
 158
 159 ex relational::op(size_t i) const
 160 {
 161         GINAC_ASSERT(i<2);
 162
 163         return i==0 ? lh : rh;
 164 }
 165
 166 ex relational::map(map_function & f) const
 167 {
 168         const ex &mapped_lh = f(lh);
 169         const ex &mapped_rh = f(rh);
 170
 171         if (!are_ex_trivially_equal(lh, mapped_lh)
 172          || !are_ex_trivially_equal(rh, mapped_rh))
 173                 return (new relational(mapped_lh, mapped_rh, o))->setflag(status_flags::dynallocated);
 174         else
 175                 return *this;
 176 }
 177
 178 ex relational::eval(int level) const
 179 {
 180         if (level==1)
 181                 return this->hold();
 182
 183         if (level == -max_recursion_level)
 184                 throw(std::runtime_error("max recursion level reached"));
 185
 186         return (new relational(lh.eval(level-1),rh.eval(level-1),o))->setflag(status_flags::dynallocated | status_flags::evaluated);
 187 }
 188
 189 ex relational::subs(const exmap & m, unsigned options) const
 190 {
 191         const ex & subsed_lh = lh.subs(m, options);
 192         const ex & subsed_rh = rh.subs(m, options);
 193
 194         if (!are_ex_trivially_equal(lh, subsed_lh) || !are_ex_trivially_equal(rh, subsed_rh))
 195                 return relational(subsed_lh, subsed_rh, o).subs_one_level(m, options);
 196         else
 197                 return subs_one_level(m, options);
 198 }
 199
 200 ex relational::eval_ncmul(const exvector & v) const
 201 {
 202         return lh.eval_ncmul(v);
 203 }
 204
 205 // protected
 206
 207 int relational::compare_same_type(const basic & other) const
 208 {
 209         GINAC_ASSERT(is_exactly_a<relational>(other));
 210         const relational &oth = static_cast<const relational &>(other);
 211         if (o==oth.o && lh.is_equal(oth.lh) && rh.is_equal(oth.rh))
 212                 return 0;
 213         switch (o) {
 214                 case equal:
 215                 case not_equal:
 216                         if (oth.o!=o)
 217                                 return (o < oth.o) ? -1 : 1;
 218                         break;
 219                 case less:
 220                         if (oth.o!=greater)
 221                                 return (o < oth.o) ? -1 : 1;
 222                         break;
 223                 case less_or_equal:
 224                         if (oth.o!=greater_or_equal)
 225                                 return (o < oth.o) ? -1 : 1;
 226                         break;
 227                 case greater:
 228                         if (oth.o!=less)
 229                                 return (o < oth.o) ? -1 : 1;
 230                         break;
 231                 case greater_or_equal:
 232                         if (oth.o!=less_or_equal)
 233                                 return (o < oth.o) ? -1 : 1;
 234                         break;
 235         }
 236         const int lcmpval = lh.compare(oth.rh);
 237         return (lcmpval!=0) ? lcmpval : rh.compare(oth.lh);
 238 }
 239
 240 bool relational::match_same_type(const basic & other) const
 241 {
 242         GINAC_ASSERT(is_exactly_a<relational>(other));
 243         const relational &oth = static_cast<const relational &>(other);
 244
 245         return o == oth.o;
 246 }
 247
 248 unsigned relational::return_type() const
 249 {
 250         GINAC_ASSERT(lh.return_type()==rh.return_type());
 251         return lh.return_type();
 252 }
 253
 254 return_type_t relational::return_type_tinfo() const
 255 {
 256         GINAC_ASSERT(lh.return_type_tinfo()==rh.return_type_tinfo());
 257         return lh.return_type_tinfo();
 258 }
 259
 260 unsigned relational::calchash() const
 261 {
 262         const void* this_tinfo = (const void*)typeid(*this).name();
 263         unsigned v = golden_ratio_hash((p_int)this_tinfo);
 264         unsigned lhash = lh.gethash();
 265         unsigned rhash = rh.gethash();
 266
 267         v = rotate_left(v);
 268         switch(o) {
 269                 case equal:
 270                 case not_equal:
 271                         if (lhash>rhash) {
 272                                 v ^= lhash;
 273                                 lhash = rhash;
 274                         } else {
 275                                 v ^= rhash;
 276                         }
 277                         break;
 278                 case less:
 279                 case less_or_equal:
 280                         v ^= rhash;
 281                         break;
 282                 case greater:
 283                 case greater_or_equal:
 284                         v ^= lhash;
 285                         lhash = rhash;
 286                         break;
 287         }
 288         v = rotate_left(v);
 289         v ^= lhash;
 290
 291         // store calculated hash value only if object is already evaluated
 292         if (flags & status_flags::evaluated) {
 293                 setflag(status_flags::hash_calculated);
 294                 hashvalue = v;
 295         }
 296
 297         return v;
 298 }
 299
 300 //////////
 301 // new virtual functions which can be overridden by derived classes
 302 //////////
 303
 304 /** Left hand side of relational. */
 305 ex relational::lhs() const
 306 {
 307         return lh;
 308 }
 309
 310 /** Right hand side of relational. */
 311 ex relational::rhs() const
 312 {
 313         return rh;
 314 }
 315
 316 //////////
 317 // non-virtual functions in this class
 318 //////////
 319
 320 relational::safe_bool relational::make_safe_bool(bool cond) const
 321 {
 322         return cond? &safe_bool_helper::nonnull : 0;
 323 }
 324
 325 /** Cast the relational into a boolean, mainly for evaluation within an
 326  *  if-statement.  Note that (a<b) == false does not imply (a>=b) == true in
 327  *  the general symbolic case.  A false result means the comparison is either
 328  *  false or undecidable (except of course for !=, where true means either
 329  *  unequal or undecidable). */
 330 relational::operator relational::safe_bool() const
 331 {
 332         const ex df = lh-rh;
 333         if (!is_exactly_a<numeric>(df))
 334                 // cannot decide on non-numerical results
 335                 return o==not_equal ? make_safe_bool(true) : make_safe_bool(false);
 336
 337         switch (o) {
 338                 case equal:
 339                         return make_safe_bool(ex_to<numeric>(df).is_zero());
 340                 case not_equal:
 341                         return make_safe_bool(!ex_to<numeric>(df).is_zero());
 342                 case less:
 343                         return make_safe_bool(ex_to<numeric>(df)<(*_num0_p));
 344                 case less_or_equal:
 345                         return make_safe_bool(ex_to<numeric>(df)<=(*_num0_p));
 346                 case greater:
 347                         return make_safe_bool(ex_to<numeric>(df)>(*_num0_p));
 348                 case greater_or_equal:
 349                         return make_safe_bool(ex_to<numeric>(df)>=(*_num0_p));
 350                 default:
 351                         throw(std::logic_error("invalid relational operator"));
 352         }
 353 }
 354
 355 } // namespace GiNaC