3 * This file implements several functions that work on univariate and
4 * multivariate polynomials and rational functions.
5 * These functions include polynomial quotient and remainder, GCD and LCM
6 * computation, square-free factorization and rational function normalization. */
9 * GiNaC Copyright (C) 1999-2005 Johannes Gutenberg University Mainz, Germany
11 * This program is free software; you can redistribute it and/or modify
12 * it under the terms of the GNU General Public License as published by
13 * the Free Software Foundation; either version 2 of the License, or
14 * (at your option) any later version.
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU General Public License for more details.
21 * You should have received a copy of the GNU General Public License
22 * along with this program; if not, write to the Free Software
23 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
34 #include "expairseq.h"
41 #include "relational.h"
42 #include "operators.h"
50 // If comparing expressions (ex::compare()) is fast, you can set this to 1.
51 // Some routines like quo(), rem() and gcd() will then return a quick answer
52 // when they are called with two identical arguments.
53 #define FAST_COMPARE 1
55 // Set this if you want divide_in_z() to use remembering
56 #define USE_REMEMBER 0
58 // Set this if you want divide_in_z() to use trial division followed by
59 // polynomial interpolation (always slower except for completely dense
61 #define USE_TRIAL_DIVISION 0
63 // Set this to enable some statistical output for the GCD routines
68 // Statistics variables
69 static int gcd_called = 0;
70 static int sr_gcd_called = 0;
71 static int heur_gcd_called = 0;
72 static int heur_gcd_failed = 0;
74 // Print statistics at end of program
75 static struct _stat_print {
78 std::cout << "gcd() called " << gcd_called << " times\n";
79 std::cout << "sr_gcd() called " << sr_gcd_called << " times\n";
80 std::cout << "heur_gcd() called " << heur_gcd_called << " times\n";
81 std::cout << "heur_gcd() failed " << heur_gcd_failed << " times\n";
87 /** Return pointer to first symbol found in expression. Due to GiNaC's
88 * internal ordering of terms, it may not be obvious which symbol this
89 * function returns for a given expression.
91 * @param e expression to search
92 * @param x first symbol found (returned)
93 * @return "false" if no symbol was found, "true" otherwise */
94 static bool get_first_symbol(const ex &e, ex &x)
96 if (is_a<symbol>(e)) {
99 } else if (is_exactly_a<add>(e) || is_exactly_a<mul>(e)) {
100 for (size_t i=0; i<e.nops(); i++)
101 if (get_first_symbol(e.op(i), x))
103 } else if (is_exactly_a<power>(e)) {
104 if (get_first_symbol(e.op(0), x))
112 * Statistical information about symbols in polynomials
115 /** This structure holds information about the highest and lowest degrees
116 * in which a symbol appears in two multivariate polynomials "a" and "b".
117 * A vector of these structures with information about all symbols in
118 * two polynomials can be created with the function get_symbol_stats().
120 * @see get_symbol_stats */
122 /** Reference to symbol */
125 /** Highest degree of symbol in polynomial "a" */
128 /** Highest degree of symbol in polynomial "b" */
131 /** Lowest degree of symbol in polynomial "a" */
134 /** Lowest degree of symbol in polynomial "b" */
137 /** Maximum of deg_a and deg_b (Used for sorting) */
140 /** Maximum number of terms of leading coefficient of symbol in both polynomials */
143 /** Commparison operator for sorting */
144 bool operator<(const sym_desc &x) const
146 if (max_deg == x.max_deg)
147 return max_lcnops < x.max_lcnops;
149 return max_deg < x.max_deg;
153 // Vector of sym_desc structures
154 typedef std::vector<sym_desc> sym_desc_vec;
156 // Add symbol the sym_desc_vec (used internally by get_symbol_stats())
157 static void add_symbol(const ex &s, sym_desc_vec &v)
159 sym_desc_vec::const_iterator it = v.begin(), itend = v.end();
160 while (it != itend) {
161 if (it->sym.is_equal(s)) // If it's already in there, don't add it a second time
170 // Collect all symbols of an expression (used internally by get_symbol_stats())
171 static void collect_symbols(const ex &e, sym_desc_vec &v)
173 if (is_a<symbol>(e)) {
175 } else if (is_exactly_a<add>(e) || is_exactly_a<mul>(e)) {
176 for (size_t i=0; i<e.nops(); i++)
177 collect_symbols(e.op(i), v);
178 } else if (is_exactly_a<power>(e)) {
179 collect_symbols(e.op(0), v);
183 /** Collect statistical information about symbols in polynomials.
184 * This function fills in a vector of "sym_desc" structs which contain
185 * information about the highest and lowest degrees of all symbols that
186 * appear in two polynomials. The vector is then sorted by minimum
187 * degree (lowest to highest). The information gathered by this
188 * function is used by the GCD routines to identify trivial factors
189 * and to determine which variable to choose as the main variable
190 * for GCD computation.
192 * @param a first multivariate polynomial
193 * @param b second multivariate polynomial
194 * @param v vector of sym_desc structs (filled in) */
195 static void get_symbol_stats(const ex &a, const ex &b, sym_desc_vec &v)
197 collect_symbols(a.eval(), v); // eval() to expand assigned symbols
198 collect_symbols(b.eval(), v);
199 sym_desc_vec::iterator it = v.begin(), itend = v.end();
200 while (it != itend) {
201 int deg_a = a.degree(it->sym);
202 int deg_b = b.degree(it->sym);
205 it->max_deg = std::max(deg_a, deg_b);
206 it->max_lcnops = std::max(a.lcoeff(it->sym).nops(), b.lcoeff(it->sym).nops());
207 it->ldeg_a = a.ldegree(it->sym);
208 it->ldeg_b = b.ldegree(it->sym);
211 std::sort(v.begin(), v.end());
214 std::clog << "Symbols:\n";
215 it = v.begin(); itend = v.end();
216 while (it != itend) {
217 std::clog << " " << it->sym << ": deg_a=" << it->deg_a << ", deg_b=" << it->deg_b << ", ldeg_a=" << it->ldeg_a << ", ldeg_b=" << it->ldeg_b << ", max_deg=" << it->max_deg << ", max_lcnops=" << it->max_lcnops << endl;
218 std::clog << " lcoeff_a=" << a.lcoeff(it->sym) << ", lcoeff_b=" << b.lcoeff(it->sym) << endl;
226 * Computation of LCM of denominators of coefficients of a polynomial
229 // Compute LCM of denominators of coefficients by going through the
230 // expression recursively (used internally by lcm_of_coefficients_denominators())
231 static numeric lcmcoeff(const ex &e, const numeric &l)
233 if (e.info(info_flags::rational))
234 return lcm(ex_to<numeric>(e).denom(), l);
235 else if (is_exactly_a<add>(e)) {
237 for (size_t i=0; i<e.nops(); i++)
238 c = lcmcoeff(e.op(i), c);
240 } else if (is_exactly_a<mul>(e)) {
242 for (size_t i=0; i<e.nops(); i++)
243 c *= lcmcoeff(e.op(i), _num1);
245 } else if (is_exactly_a<power>(e)) {
246 if (is_a<symbol>(e.op(0)))
249 return pow(lcmcoeff(e.op(0), l), ex_to<numeric>(e.op(1)));
254 /** Compute LCM of denominators of coefficients of a polynomial.
255 * Given a polynomial with rational coefficients, this function computes
256 * the LCM of the denominators of all coefficients. This can be used
257 * to bring a polynomial from Q[X] to Z[X].
259 * @param e multivariate polynomial (need not be expanded)
260 * @return LCM of denominators of coefficients */
261 static numeric lcm_of_coefficients_denominators(const ex &e)
263 return lcmcoeff(e, _num1);
266 /** Bring polynomial from Q[X] to Z[X] by multiplying in the previously
267 * determined LCM of the coefficient's denominators.
269 * @param e multivariate polynomial (need not be expanded)
270 * @param lcm LCM to multiply in */
271 static ex multiply_lcm(const ex &e, const numeric &lcm)
273 if (is_exactly_a<mul>(e)) {
274 size_t num = e.nops();
275 exvector v; v.reserve(num + 1);
276 numeric lcm_accum = _num1;
277 for (size_t i=0; i<num; i++) {
278 numeric op_lcm = lcmcoeff(e.op(i), _num1);
279 v.push_back(multiply_lcm(e.op(i), op_lcm));
282 v.push_back(lcm / lcm_accum);
283 return (new mul(v))->setflag(status_flags::dynallocated);
284 } else if (is_exactly_a<add>(e)) {
285 size_t num = e.nops();
286 exvector v; v.reserve(num);
287 for (size_t i=0; i<num; i++)
288 v.push_back(multiply_lcm(e.op(i), lcm));
289 return (new add(v))->setflag(status_flags::dynallocated);
290 } else if (is_exactly_a<power>(e)) {
291 if (is_a<symbol>(e.op(0)))
294 return pow(multiply_lcm(e.op(0), lcm.power(ex_to<numeric>(e.op(1)).inverse())), e.op(1));
300 /** Compute the integer content (= GCD of all numeric coefficients) of an
301 * expanded polynomial. For a polynomial with rational coefficients, this
302 * returns g/l where g is the GCD of the coefficients' numerators and l
303 * is the LCM of the coefficients' denominators.
305 * @return integer content */
306 numeric ex::integer_content() const
308 return bp->integer_content();
311 numeric basic::integer_content() const
316 numeric numeric::integer_content() const
321 numeric add::integer_content() const
323 epvector::const_iterator it = seq.begin();
324 epvector::const_iterator itend = seq.end();
325 numeric c = _num0, l = _num1;
326 while (it != itend) {
327 GINAC_ASSERT(!is_exactly_a<numeric>(it->rest));
328 GINAC_ASSERT(is_exactly_a<numeric>(it->coeff));
329 c = gcd(ex_to<numeric>(it->coeff).numer(), c);
330 l = lcm(ex_to<numeric>(it->coeff).denom(), l);
333 GINAC_ASSERT(is_exactly_a<numeric>(overall_coeff));
334 c = gcd(ex_to<numeric>(overall_coeff).numer(), c);
335 l = lcm(ex_to<numeric>(overall_coeff).denom(), l);
339 numeric mul::integer_content() const
341 #ifdef DO_GINAC_ASSERT
342 epvector::const_iterator it = seq.begin();
343 epvector::const_iterator itend = seq.end();
344 while (it != itend) {
345 GINAC_ASSERT(!is_exactly_a<numeric>(recombine_pair_to_ex(*it)));
348 #endif // def DO_GINAC_ASSERT
349 GINAC_ASSERT(is_exactly_a<numeric>(overall_coeff));
350 return abs(ex_to<numeric>(overall_coeff));
355 * Polynomial quotients and remainders
358 /** Quotient q(x) of polynomials a(x) and b(x) in Q[x].
359 * It satisfies a(x)=b(x)*q(x)+r(x).
361 * @param a first polynomial in x (dividend)
362 * @param b second polynomial in x (divisor)
363 * @param x a and b are polynomials in x
364 * @param check_args check whether a and b are polynomials with rational
365 * coefficients (defaults to "true")
366 * @return quotient of a and b in Q[x] */
367 ex quo(const ex &a, const ex &b, const ex &x, bool check_args)
370 throw(std::overflow_error("quo: division by zero"));
371 if (is_exactly_a<numeric>(a) && is_exactly_a<numeric>(b))
377 if (check_args && (!a.info(info_flags::rational_polynomial) || !b.info(info_flags::rational_polynomial)))
378 throw(std::invalid_argument("quo: arguments must be polynomials over the rationals"));
380 // Polynomial long division
384 int bdeg = b.degree(x);
385 int rdeg = r.degree(x);
386 ex blcoeff = b.expand().coeff(x, bdeg);
387 bool blcoeff_is_numeric = is_exactly_a<numeric>(blcoeff);
388 exvector v; v.reserve(std::max(rdeg - bdeg + 1, 0));
389 while (rdeg >= bdeg) {
390 ex term, rcoeff = r.coeff(x, rdeg);
391 if (blcoeff_is_numeric)
392 term = rcoeff / blcoeff;
394 if (!divide(rcoeff, blcoeff, term, false))
395 return (new fail())->setflag(status_flags::dynallocated);
397 term *= power(x, rdeg - bdeg);
399 r -= (term * b).expand();
404 return (new add(v))->setflag(status_flags::dynallocated);
408 /** Remainder r(x) of polynomials a(x) and b(x) in Q[x].
409 * It satisfies a(x)=b(x)*q(x)+r(x).
411 * @param a first polynomial in x (dividend)
412 * @param b second polynomial in x (divisor)
413 * @param x a and b are polynomials in x
414 * @param check_args check whether a and b are polynomials with rational
415 * coefficients (defaults to "true")
416 * @return remainder of a(x) and b(x) in Q[x] */
417 ex rem(const ex &a, const ex &b, const ex &x, bool check_args)
420 throw(std::overflow_error("rem: division by zero"));
421 if (is_exactly_a<numeric>(a)) {
422 if (is_exactly_a<numeric>(b))
431 if (check_args && (!a.info(info_flags::rational_polynomial) || !b.info(info_flags::rational_polynomial)))
432 throw(std::invalid_argument("rem: arguments must be polynomials over the rationals"));
434 // Polynomial long division
438 int bdeg = b.degree(x);
439 int rdeg = r.degree(x);
440 ex blcoeff = b.expand().coeff(x, bdeg);
441 bool blcoeff_is_numeric = is_exactly_a<numeric>(blcoeff);
442 while (rdeg >= bdeg) {
443 ex term, rcoeff = r.coeff(x, rdeg);
444 if (blcoeff_is_numeric)
445 term = rcoeff / blcoeff;
447 if (!divide(rcoeff, blcoeff, term, false))
448 return (new fail())->setflag(status_flags::dynallocated);
450 term *= power(x, rdeg - bdeg);
451 r -= (term * b).expand();
460 /** Decompose rational function a(x)=N(x)/D(x) into P(x)+n(x)/D(x)
461 * with degree(n, x) < degree(D, x).
463 * @param a rational function in x
464 * @param x a is a function of x
465 * @return decomposed function. */
466 ex decomp_rational(const ex &a, const ex &x)
468 ex nd = numer_denom(a);
469 ex numer = nd.op(0), denom = nd.op(1);
470 ex q = quo(numer, denom, x);
471 if (is_exactly_a<fail>(q))
474 return q + rem(numer, denom, x) / denom;
478 /** Pseudo-remainder of polynomials a(x) and b(x) in Q[x].
480 * @param a first polynomial in x (dividend)
481 * @param b second polynomial in x (divisor)
482 * @param x a and b are polynomials in x
483 * @param check_args check whether a and b are polynomials with rational
484 * coefficients (defaults to "true")
485 * @return pseudo-remainder of a(x) and b(x) in Q[x] */
486 ex prem(const ex &a, const ex &b, const ex &x, bool check_args)
489 throw(std::overflow_error("prem: division by zero"));
490 if (is_exactly_a<numeric>(a)) {
491 if (is_exactly_a<numeric>(b))
496 if (check_args && (!a.info(info_flags::rational_polynomial) || !b.info(info_flags::rational_polynomial)))
497 throw(std::invalid_argument("prem: arguments must be polynomials over the rationals"));
499 // Polynomial long division
502 int rdeg = r.degree(x);
503 int bdeg = eb.degree(x);
506 blcoeff = eb.coeff(x, bdeg);
510 eb -= blcoeff * power(x, bdeg);
514 int delta = rdeg - bdeg + 1, i = 0;
515 while (rdeg >= bdeg && !r.is_zero()) {
516 ex rlcoeff = r.coeff(x, rdeg);
517 ex term = (power(x, rdeg - bdeg) * eb * rlcoeff).expand();
521 r -= rlcoeff * power(x, rdeg);
522 r = (blcoeff * r).expand() - term;
526 return power(blcoeff, delta - i) * r;
530 /** Sparse pseudo-remainder of polynomials a(x) and b(x) in Q[x].
532 * @param a first polynomial in x (dividend)
533 * @param b second polynomial in x (divisor)
534 * @param x a and b are polynomials in x
535 * @param check_args check whether a and b are polynomials with rational
536 * coefficients (defaults to "true")
537 * @return sparse pseudo-remainder of a(x) and b(x) in Q[x] */
538 ex sprem(const ex &a, const ex &b, const ex &x, bool check_args)
541 throw(std::overflow_error("prem: division by zero"));
542 if (is_exactly_a<numeric>(a)) {
543 if (is_exactly_a<numeric>(b))
548 if (check_args && (!a.info(info_flags::rational_polynomial) || !b.info(info_flags::rational_polynomial)))
549 throw(std::invalid_argument("prem: arguments must be polynomials over the rationals"));
551 // Polynomial long division
554 int rdeg = r.degree(x);
555 int bdeg = eb.degree(x);
558 blcoeff = eb.coeff(x, bdeg);
562 eb -= blcoeff * power(x, bdeg);
566 while (rdeg >= bdeg && !r.is_zero()) {
567 ex rlcoeff = r.coeff(x, rdeg);
568 ex term = (power(x, rdeg - bdeg) * eb * rlcoeff).expand();
572 r -= rlcoeff * power(x, rdeg);
573 r = (blcoeff * r).expand() - term;
580 /** Exact polynomial division of a(X) by b(X) in Q[X].
582 * @param a first multivariate polynomial (dividend)
583 * @param b second multivariate polynomial (divisor)
584 * @param q quotient (returned)
585 * @param check_args check whether a and b are polynomials with rational
586 * coefficients (defaults to "true")
587 * @return "true" when exact division succeeds (quotient returned in q),
588 * "false" otherwise (q left untouched) */
589 bool divide(const ex &a, const ex &b, ex &q, bool check_args)
592 throw(std::overflow_error("divide: division by zero"));
597 if (is_exactly_a<numeric>(b)) {
600 } else if (is_exactly_a<numeric>(a))
608 if (check_args && (!a.info(info_flags::rational_polynomial) ||
609 !b.info(info_flags::rational_polynomial)))
610 throw(std::invalid_argument("divide: arguments must be polynomials over the rationals"));
614 if (!get_first_symbol(a, x) && !get_first_symbol(b, x))
615 throw(std::invalid_argument("invalid expression in divide()"));
617 // Polynomial long division (recursive)
623 int bdeg = b.degree(x);
624 int rdeg = r.degree(x);
625 ex blcoeff = b.expand().coeff(x, bdeg);
626 bool blcoeff_is_numeric = is_exactly_a<numeric>(blcoeff);
627 exvector v; v.reserve(std::max(rdeg - bdeg + 1, 0));
628 while (rdeg >= bdeg) {
629 ex term, rcoeff = r.coeff(x, rdeg);
630 if (blcoeff_is_numeric)
631 term = rcoeff / blcoeff;
633 if (!divide(rcoeff, blcoeff, term, false))
635 term *= power(x, rdeg - bdeg);
637 r -= (term * b).expand();
639 q = (new add(v))->setflag(status_flags::dynallocated);
653 typedef std::pair<ex, ex> ex2;
654 typedef std::pair<ex, bool> exbool;
657 bool operator() (const ex2 &p, const ex2 &q) const
659 int cmp = p.first.compare(q.first);
660 return ((cmp<0) || (!(cmp>0) && p.second.compare(q.second)<0));
664 typedef std::map<ex2, exbool, ex2_less> ex2_exbool_remember;
668 /** Exact polynomial division of a(X) by b(X) in Z[X].
669 * This functions works like divide() but the input and output polynomials are
670 * in Z[X] instead of Q[X] (i.e. they have integer coefficients). Unlike
671 * divide(), it doesn't check whether the input polynomials really are integer
672 * polynomials, so be careful of what you pass in. Also, you have to run
673 * get_symbol_stats() over the input polynomials before calling this function
674 * and pass an iterator to the first element of the sym_desc vector. This
675 * function is used internally by the heur_gcd().
677 * @param a first multivariate polynomial (dividend)
678 * @param b second multivariate polynomial (divisor)
679 * @param q quotient (returned)
680 * @param var iterator to first element of vector of sym_desc structs
681 * @return "true" when exact division succeeds (the quotient is returned in
682 * q), "false" otherwise.
683 * @see get_symbol_stats, heur_gcd */
684 static bool divide_in_z(const ex &a, const ex &b, ex &q, sym_desc_vec::const_iterator var)
688 throw(std::overflow_error("divide_in_z: division by zero"));
689 if (b.is_equal(_ex1)) {
693 if (is_exactly_a<numeric>(a)) {
694 if (is_exactly_a<numeric>(b)) {
696 return q.info(info_flags::integer);
709 static ex2_exbool_remember dr_remember;
710 ex2_exbool_remember::const_iterator remembered = dr_remember.find(ex2(a, b));
711 if (remembered != dr_remember.end()) {
712 q = remembered->second.first;
713 return remembered->second.second;
718 const ex &x = var->sym;
721 int adeg = a.degree(x), bdeg = b.degree(x);
725 #if USE_TRIAL_DIVISION
727 // Trial division with polynomial interpolation
730 // Compute values at evaluation points 0..adeg
731 vector<numeric> alpha; alpha.reserve(adeg + 1);
732 exvector u; u.reserve(adeg + 1);
733 numeric point = _num0;
735 for (i=0; i<=adeg; i++) {
736 ex bs = b.subs(x == point, subs_options::no_pattern);
737 while (bs.is_zero()) {
739 bs = b.subs(x == point, subs_options::no_pattern);
741 if (!divide_in_z(a.subs(x == point, subs_options::no_pattern), bs, c, var+1))
743 alpha.push_back(point);
749 vector<numeric> rcp; rcp.reserve(adeg + 1);
750 rcp.push_back(_num0);
751 for (k=1; k<=adeg; k++) {
752 numeric product = alpha[k] - alpha[0];
754 product *= alpha[k] - alpha[i];
755 rcp.push_back(product.inverse());
758 // Compute Newton coefficients
759 exvector v; v.reserve(adeg + 1);
761 for (k=1; k<=adeg; k++) {
763 for (i=k-2; i>=0; i--)
764 temp = temp * (alpha[k] - alpha[i]) + v[i];
765 v.push_back((u[k] - temp) * rcp[k]);
768 // Convert from Newton form to standard form
770 for (k=adeg-1; k>=0; k--)
771 c = c * (x - alpha[k]) + v[k];
773 if (c.degree(x) == (adeg - bdeg)) {
781 // Polynomial long division (recursive)
787 ex blcoeff = eb.coeff(x, bdeg);
788 exvector v; v.reserve(std::max(rdeg - bdeg + 1, 0));
789 while (rdeg >= bdeg) {
790 ex term, rcoeff = r.coeff(x, rdeg);
791 if (!divide_in_z(rcoeff, blcoeff, term, var+1))
793 term = (term * power(x, rdeg - bdeg)).expand();
795 r -= (term * eb).expand();
797 q = (new add(v))->setflag(status_flags::dynallocated);
799 dr_remember[ex2(a, b)] = exbool(q, true);
806 dr_remember[ex2(a, b)] = exbool(q, false);
815 * Separation of unit part, content part and primitive part of polynomials
818 /** Compute unit part (= sign of leading coefficient) of a multivariate
819 * polynomial in Q[x]. The product of unit part, content part, and primitive
820 * part is the polynomial itself.
822 * @param x main variable
824 * @see ex::content, ex::primpart, ex::unitcontprim */
825 ex ex::unit(const ex &x) const
827 ex c = expand().lcoeff(x);
828 if (is_exactly_a<numeric>(c))
829 return c.info(info_flags::negative) ?_ex_1 : _ex1;
832 if (get_first_symbol(c, y))
835 throw(std::invalid_argument("invalid expression in unit()"));
840 /** Compute content part (= unit normal GCD of all coefficients) of a
841 * multivariate polynomial in Q[x]. The product of unit part, content part,
842 * and primitive part is the polynomial itself.
844 * @param x main variable
845 * @return content part
846 * @see ex::unit, ex::primpart, ex::unitcontprim */
847 ex ex::content(const ex &x) const
849 if (is_exactly_a<numeric>(*this))
850 return info(info_flags::negative) ? -*this : *this;
856 // First, divide out the integer content (which we can calculate very efficiently).
857 // If the leading coefficient of the quotient is an integer, we are done.
858 ex c = e.integer_content();
860 int deg = r.degree(x);
861 ex lcoeff = r.coeff(x, deg);
862 if (lcoeff.info(info_flags::integer))
865 // GCD of all coefficients
866 int ldeg = r.ldegree(x);
868 return lcoeff * c / lcoeff.unit(x);
870 for (int i=ldeg; i<=deg; i++)
871 cont = gcd(r.coeff(x, i), cont, NULL, NULL, false);
876 /** Compute primitive part of a multivariate polynomial in Q[x]. The result
877 * will be a unit-normal polynomial with a content part of 1. The product
878 * of unit part, content part, and primitive part is the polynomial itself.
880 * @param x main variable
881 * @return primitive part
882 * @see ex::unit, ex::content, ex::unitcontprim */
883 ex ex::primpart(const ex &x) const
885 // We need to compute the unit and content anyway, so call unitcontprim()
887 unitcontprim(x, u, c, p);
892 /** Compute primitive part of a multivariate polynomial in Q[x] when the
893 * content part is already known. This function is faster in computing the
894 * primitive part than the previous function.
896 * @param x main variable
897 * @param c previously computed content part
898 * @return primitive part */
899 ex ex::primpart(const ex &x, const ex &c) const
901 if (is_zero() || c.is_zero())
903 if (is_exactly_a<numeric>(*this))
906 // Divide by unit and content to get primitive part
908 if (is_exactly_a<numeric>(c))
909 return *this / (c * u);
911 return quo(*this, c * u, x, false);
915 /** Compute unit part, content part, and primitive part of a multivariate
916 * polynomial in Q[x]. The product of the three parts is the polynomial
919 * @param x main variable
920 * @param u unit part (returned)
921 * @param c content part (returned)
922 * @param p primitive part (returned)
923 * @see ex::unit, ex::content, ex::primpart */
924 void ex::unitcontprim(const ex &x, ex &u, ex &c, ex &p) const
926 // Quick check for zero (avoid expanding)
933 // Special case: input is a number
934 if (is_exactly_a<numeric>(*this)) {
935 if (info(info_flags::negative)) {
937 c = abs(ex_to<numeric>(*this));
946 // Expand input polynomial
954 // Compute unit and content
958 // Divide by unit and content to get primitive part
963 if (is_exactly_a<numeric>(c))
966 p = quo(e, c * u, x, false);
971 * GCD of multivariate polynomials
974 /** Compute GCD of multivariate polynomials using the subresultant PRS
975 * algorithm. This function is used internally by gcd().
977 * @param a first multivariate polynomial
978 * @param b second multivariate polynomial
979 * @param var iterator to first element of vector of sym_desc structs
980 * @return the GCD as a new expression
983 static ex sr_gcd(const ex &a, const ex &b, sym_desc_vec::const_iterator var)
989 // The first symbol is our main variable
990 const ex &x = var->sym;
992 // Sort c and d so that c has higher degree
994 int adeg = a.degree(x), bdeg = b.degree(x);
1008 // Remove content from c and d, to be attached to GCD later
1009 ex cont_c = c.content(x);
1010 ex cont_d = d.content(x);
1011 ex gamma = gcd(cont_c, cont_d, NULL, NULL, false);
1014 c = c.primpart(x, cont_c);
1015 d = d.primpart(x, cont_d);
1017 // First element of subresultant sequence
1018 ex r = _ex0, ri = _ex1, psi = _ex1;
1019 int delta = cdeg - ddeg;
1023 // Calculate polynomial pseudo-remainder
1024 r = prem(c, d, x, false);
1026 return gamma * d.primpart(x);
1030 if (!divide_in_z(r, ri * pow(psi, delta), d, var))
1031 throw(std::runtime_error("invalid expression in sr_gcd(), division failed"));
1034 if (is_exactly_a<numeric>(r))
1037 return gamma * r.primpart(x);
1040 // Next element of subresultant sequence
1041 ri = c.expand().lcoeff(x);
1045 divide_in_z(pow(ri, delta), pow(psi, delta-1), psi, var+1);
1046 delta = cdeg - ddeg;
1051 /** Return maximum (absolute value) coefficient of a polynomial.
1052 * This function is used internally by heur_gcd().
1054 * @return maximum coefficient
1056 numeric ex::max_coefficient() const
1058 return bp->max_coefficient();
1061 /** Implementation ex::max_coefficient().
1063 numeric basic::max_coefficient() const
1068 numeric numeric::max_coefficient() const
1073 numeric add::max_coefficient() const
1075 epvector::const_iterator it = seq.begin();
1076 epvector::const_iterator itend = seq.end();
1077 GINAC_ASSERT(is_exactly_a<numeric>(overall_coeff));
1078 numeric cur_max = abs(ex_to<numeric>(overall_coeff));
1079 while (it != itend) {
1081 GINAC_ASSERT(!is_exactly_a<numeric>(it->rest));
1082 a = abs(ex_to<numeric>(it->coeff));
1090 numeric mul::max_coefficient() const
1092 #ifdef DO_GINAC_ASSERT
1093 epvector::const_iterator it = seq.begin();
1094 epvector::const_iterator itend = seq.end();
1095 while (it != itend) {
1096 GINAC_ASSERT(!is_exactly_a<numeric>(recombine_pair_to_ex(*it)));
1099 #endif // def DO_GINAC_ASSERT
1100 GINAC_ASSERT(is_exactly_a<numeric>(overall_coeff));
1101 return abs(ex_to<numeric>(overall_coeff));
1105 /** Apply symmetric modular homomorphism to an expanded multivariate
1106 * polynomial. This function is usually used internally by heur_gcd().
1109 * @return mapped polynomial
1111 ex basic::smod(const numeric &xi) const
1116 ex numeric::smod(const numeric &xi) const
1118 return GiNaC::smod(*this, xi);
1121 ex add::smod(const numeric &xi) const
1124 newseq.reserve(seq.size()+1);
1125 epvector::const_iterator it = seq.begin();
1126 epvector::const_iterator itend = seq.end();
1127 while (it != itend) {
1128 GINAC_ASSERT(!is_exactly_a<numeric>(it->rest));
1129 numeric coeff = GiNaC::smod(ex_to<numeric>(it->coeff), xi);
1130 if (!coeff.is_zero())
1131 newseq.push_back(expair(it->rest, coeff));
1134 GINAC_ASSERT(is_exactly_a<numeric>(overall_coeff));
1135 numeric coeff = GiNaC::smod(ex_to<numeric>(overall_coeff), xi);
1136 return (new add(newseq,coeff))->setflag(status_flags::dynallocated);
1139 ex mul::smod(const numeric &xi) const
1141 #ifdef DO_GINAC_ASSERT
1142 epvector::const_iterator it = seq.begin();
1143 epvector::const_iterator itend = seq.end();
1144 while (it != itend) {
1145 GINAC_ASSERT(!is_exactly_a<numeric>(recombine_pair_to_ex(*it)));
1148 #endif // def DO_GINAC_ASSERT
1149 mul * mulcopyp = new mul(*this);
1150 GINAC_ASSERT(is_exactly_a<numeric>(overall_coeff));
1151 mulcopyp->overall_coeff = GiNaC::smod(ex_to<numeric>(overall_coeff),xi);
1152 mulcopyp->clearflag(status_flags::evaluated);
1153 mulcopyp->clearflag(status_flags::hash_calculated);
1154 return mulcopyp->setflag(status_flags::dynallocated);
1158 /** xi-adic polynomial interpolation */
1159 static ex interpolate(const ex &gamma, const numeric &xi, const ex &x, int degree_hint = 1)
1161 exvector g; g.reserve(degree_hint);
1163 numeric rxi = xi.inverse();
1164 for (int i=0; !e.is_zero(); i++) {
1166 g.push_back(gi * power(x, i));
1169 return (new add(g))->setflag(status_flags::dynallocated);
1172 /** Exception thrown by heur_gcd() to signal failure. */
1173 class gcdheu_failed {};
1175 /** Compute GCD of multivariate polynomials using the heuristic GCD algorithm.
1176 * get_symbol_stats() must have been called previously with the input
1177 * polynomials and an iterator to the first element of the sym_desc vector
1178 * passed in. This function is used internally by gcd().
1180 * @param a first multivariate polynomial (expanded)
1181 * @param b second multivariate polynomial (expanded)
1182 * @param ca cofactor of polynomial a (returned), NULL to suppress
1183 * calculation of cofactor
1184 * @param cb cofactor of polynomial b (returned), NULL to suppress
1185 * calculation of cofactor
1186 * @param var iterator to first element of vector of sym_desc structs
1187 * @return the GCD as a new expression
1189 * @exception gcdheu_failed() */
1190 static ex heur_gcd(const ex &a, const ex &b, ex *ca, ex *cb, sym_desc_vec::const_iterator var)
1196 // Algorithm only works for non-vanishing input polynomials
1197 if (a.is_zero() || b.is_zero())
1198 return (new fail())->setflag(status_flags::dynallocated);
1200 // GCD of two numeric values -> CLN
1201 if (is_exactly_a<numeric>(a) && is_exactly_a<numeric>(b)) {
1202 numeric g = gcd(ex_to<numeric>(a), ex_to<numeric>(b));
1204 *ca = ex_to<numeric>(a) / g;
1206 *cb = ex_to<numeric>(b) / g;
1210 // The first symbol is our main variable
1211 const ex &x = var->sym;
1213 // Remove integer content
1214 numeric gc = gcd(a.integer_content(), b.integer_content());
1215 numeric rgc = gc.inverse();
1218 int maxdeg = std::max(p.degree(x), q.degree(x));
1220 // Find evaluation point
1221 numeric mp = p.max_coefficient();
1222 numeric mq = q.max_coefficient();
1225 xi = mq * _num2 + _num2;
1227 xi = mp * _num2 + _num2;
1230 for (int t=0; t<6; t++) {
1231 if (xi.int_length() * maxdeg > 100000) {
1232 throw gcdheu_failed();
1235 // Apply evaluation homomorphism and calculate GCD
1237 ex gamma = heur_gcd(p.subs(x == xi, subs_options::no_pattern), q.subs(x == xi, subs_options::no_pattern), &cp, &cq, var+1).expand();
1238 if (!is_exactly_a<fail>(gamma)) {
1240 // Reconstruct polynomial from GCD of mapped polynomials
1241 ex g = interpolate(gamma, xi, x, maxdeg);
1243 // Remove integer content
1244 g /= g.integer_content();
1246 // If the calculated polynomial divides both p and q, this is the GCD
1248 if (divide_in_z(p, g, ca ? *ca : dummy, var) && divide_in_z(q, g, cb ? *cb : dummy, var)) {
1254 // Next evaluation point
1255 xi = iquo(xi * isqrt(isqrt(xi)) * numeric(73794), numeric(27011));
1257 return (new fail())->setflag(status_flags::dynallocated);
1261 /** Compute GCD (Greatest Common Divisor) of multivariate polynomials a(X)
1262 * and b(X) in Z[X]. Optionally also compute the cofactors of a and b,
1263 * defined by a = ca * gcd(a, b) and b = cb * gcd(a, b).
1265 * @param a first multivariate polynomial
1266 * @param b second multivariate polynomial
1267 * @param ca pointer to expression that will receive the cofactor of a, or NULL
1268 * @param cb pointer to expression that will receive the cofactor of b, or NULL
1269 * @param check_args check whether a and b are polynomials with rational
1270 * coefficients (defaults to "true")
1271 * @return the GCD as a new expression */
1272 ex gcd(const ex &a, const ex &b, ex *ca, ex *cb, bool check_args)
1278 // GCD of numerics -> CLN
1279 if (is_exactly_a<numeric>(a) && is_exactly_a<numeric>(b)) {
1280 numeric g = gcd(ex_to<numeric>(a), ex_to<numeric>(b));
1289 *ca = ex_to<numeric>(a) / g;
1291 *cb = ex_to<numeric>(b) / g;
1298 if (check_args && (!a.info(info_flags::rational_polynomial) || !b.info(info_flags::rational_polynomial))) {
1299 throw(std::invalid_argument("gcd: arguments must be polynomials over the rationals"));
1302 // Partially factored cases (to avoid expanding large expressions)
1303 if (is_exactly_a<mul>(a)) {
1304 if (is_exactly_a<mul>(b) && b.nops() > a.nops())
1307 size_t num = a.nops();
1308 exvector g; g.reserve(num);
1309 exvector acc_ca; acc_ca.reserve(num);
1311 for (size_t i=0; i<num; i++) {
1312 ex part_ca, part_cb;
1313 g.push_back(gcd(a.op(i), part_b, &part_ca, &part_cb, check_args));
1314 acc_ca.push_back(part_ca);
1318 *ca = (new mul(acc_ca))->setflag(status_flags::dynallocated);
1321 return (new mul(g))->setflag(status_flags::dynallocated);
1322 } else if (is_exactly_a<mul>(b)) {
1323 if (is_exactly_a<mul>(a) && a.nops() > b.nops())
1326 size_t num = b.nops();
1327 exvector g; g.reserve(num);
1328 exvector acc_cb; acc_cb.reserve(num);
1330 for (size_t i=0; i<num; i++) {
1331 ex part_ca, part_cb;
1332 g.push_back(gcd(part_a, b.op(i), &part_ca, &part_cb, check_args));
1333 acc_cb.push_back(part_cb);
1339 *cb = (new mul(acc_cb))->setflag(status_flags::dynallocated);
1340 return (new mul(g))->setflag(status_flags::dynallocated);
1344 // Input polynomials of the form poly^n are sometimes also trivial
1345 if (is_exactly_a<power>(a)) {
1347 const ex& exp_a = a.op(1);
1348 if (is_exactly_a<power>(b)) {
1350 const ex& exp_b = b.op(1);
1351 if (p.is_equal(pb)) {
1352 // a = p^n, b = p^m, gcd = p^min(n, m)
1353 if (exp_a < exp_b) {
1357 *cb = power(p, exp_b - exp_a);
1358 return power(p, exp_a);
1361 *ca = power(p, exp_a - exp_b);
1364 return power(p, exp_b);
1368 ex p_gcd = gcd(p, pb, &p_co, &pb_co, check_args);
1369 if (p_gcd.is_equal(_ex1)) {
1370 // a(x) = p(x)^n, b(x) = p_b(x)^m, gcd (p, p_b) = 1 ==>
1377 // XXX: do I need to check for p_gcd = -1?
1379 // there are common factors:
1380 // a(x) = g(x)^n A(x)^n, b(x) = g(x)^m B(x)^m ==>
1381 // gcd(a, b) = g(x)^n gcd(A(x)^n, g(x)^(n-m) B(x)^m
1382 if (exp_a < exp_b) {
1383 return power(p_gcd, exp_a)*
1384 gcd(power(p_co, exp_a), power(p_gcd, exp_b-exp_a)*power(pb_co, exp_b), ca, cb, false);
1386 return power(p_gcd, exp_b)*
1387 gcd(power(p_gcd, exp_a - exp_b)*power(p_co, exp_a), power(pb_co, exp_b), ca, cb, false);
1389 } // p_gcd.is_equal(_ex1)
1393 if (p.is_equal(b)) {
1394 // a = p^n, b = p, gcd = p
1396 *ca = power(p, a.op(1) - 1);
1403 ex p_gcd = gcd(p, b, &p_co, &bpart_co, false);
1405 if (p_gcd.is_equal(_ex1)) {
1406 // a(x) = p(x)^n, gcd(p, b) = 1 ==> gcd(a, b) = 1
1413 // a(x) = g(x)^n A(x)^n, b(x) = g(x) B(x) ==> gcd(a, b) = g(x) gcd(g(x)^(n-1) A(x)^n, B(x))
1414 return p_gcd*gcd(power(p_gcd, exp_a-1)*power(p_co, exp_a), bpart_co, ca, cb, false);
1416 } // is_exactly_a<power>(b)
1418 } else if (is_exactly_a<power>(b)) {
1420 if (p.is_equal(a)) {
1421 // a = p, b = p^n, gcd = p
1425 *cb = power(p, b.op(1) - 1);
1430 const ex& exp_b(b.op(1));
1431 ex p_gcd = gcd(a, p, &apart_co, &p_co, false);
1432 if (p_gcd.is_equal(_ex1)) {
1433 // b=p(x)^n, gcd(a, p) = 1 ==> gcd(a, b) == 1
1440 // there are common factors:
1441 // a(x) = g(x) A(x), b(x) = g(x)^n B(x)^n ==> gcd = g(x) gcd(g(x)^(n-1) A(x)^n, B(x))
1443 return p_gcd*gcd(apart_co, power(p_gcd, exp_b-1)*power(p_co, exp_b), ca, cb, false);
1444 } // p_gcd.is_equal(_ex1)
1448 // Some trivial cases
1449 ex aex = a.expand(), bex = b.expand();
1450 if (aex.is_zero()) {
1457 if (bex.is_zero()) {
1464 if (aex.is_equal(_ex1) || bex.is_equal(_ex1)) {
1472 if (a.is_equal(b)) {
1481 // Gather symbol statistics
1482 sym_desc_vec sym_stats;
1483 get_symbol_stats(a, b, sym_stats);
1485 // The symbol with least degree is our main variable
1486 sym_desc_vec::const_iterator var = sym_stats.begin();
1487 const ex &x = var->sym;
1489 // Cancel trivial common factor
1490 int ldeg_a = var->ldeg_a;
1491 int ldeg_b = var->ldeg_b;
1492 int min_ldeg = std::min(ldeg_a,ldeg_b);
1494 ex common = power(x, min_ldeg);
1495 return gcd((aex / common).expand(), (bex / common).expand(), ca, cb, false) * common;
1498 // Try to eliminate variables
1499 if (var->deg_a == 0) {
1500 ex bex_u, bex_c, bex_p;
1501 bex.unitcontprim(x, bex_u, bex_c, bex_p);
1502 ex g = gcd(aex, bex_c, ca, cb, false);
1504 *cb *= bex_u * bex_p;
1506 } else if (var->deg_b == 0) {
1507 ex aex_u, aex_c, aex_p;
1508 aex.unitcontprim(x, aex_u, aex_c, aex_p);
1509 ex g = gcd(aex_c, bex, ca, cb, false);
1511 *ca *= aex_u * aex_p;
1515 // Try heuristic algorithm first, fall back to PRS if that failed
1518 g = heur_gcd(aex, bex, ca, cb, var);
1519 } catch (gcdheu_failed) {
1522 if (is_exactly_a<fail>(g)) {
1526 g = sr_gcd(aex, bex, var);
1527 if (g.is_equal(_ex1)) {
1528 // Keep cofactors factored if possible
1535 divide(aex, g, *ca, false);
1537 divide(bex, g, *cb, false);
1540 if (g.is_equal(_ex1)) {
1541 // Keep cofactors factored if possible
1553 /** Compute LCM (Least Common Multiple) of multivariate polynomials in Z[X].
1555 * @param a first multivariate polynomial
1556 * @param b second multivariate polynomial
1557 * @param check_args check whether a and b are polynomials with rational
1558 * coefficients (defaults to "true")
1559 * @return the LCM as a new expression */
1560 ex lcm(const ex &a, const ex &b, bool check_args)
1562 if (is_exactly_a<numeric>(a) && is_exactly_a<numeric>(b))
1563 return lcm(ex_to<numeric>(a), ex_to<numeric>(b));
1564 if (check_args && (!a.info(info_flags::rational_polynomial) || !b.info(info_flags::rational_polynomial)))
1565 throw(std::invalid_argument("lcm: arguments must be polynomials over the rationals"));
1568 ex g = gcd(a, b, &ca, &cb, false);
1574 * Square-free factorization
1577 /** Compute square-free factorization of multivariate polynomial a(x) using
1578 * Yun's algorithm. Used internally by sqrfree().
1580 * @param a multivariate polynomial over Z[X], treated here as univariate
1582 * @param x variable to factor in
1583 * @return vector of factors sorted in ascending degree */
1584 static exvector sqrfree_yun(const ex &a, const symbol &x)
1590 if (g.is_equal(_ex1)) {
1601 } while (!z.is_zero());
1606 /** Compute a square-free factorization of a multivariate polynomial in Q[X].
1608 * @param a multivariate polynomial over Q[X]
1609 * @param l lst of variables to factor in, may be left empty for autodetection
1610 * @return a square-free factorization of \p a.
1613 * A polynomial \f$p(X) \in C[X]\f$ is said <EM>square-free</EM>
1614 * if, whenever any two polynomials \f$q(X)\f$ and \f$r(X)\f$
1617 * p(X) = q(X)^2 r(X),
1619 * we have \f$q(X) \in C\f$.
1620 * This means that \f$p(X)\f$ has no repeated factors, apart
1621 * eventually from constants.
1622 * Given a polynomial \f$p(X) \in C[X]\f$, we say that the
1625 * p(X) = b \cdot p_1(X)^{a_1} \cdot p_2(X)^{a_2} \cdots p_r(X)^{a_r}
1627 * is a <EM>square-free factorization</EM> of \f$p(X)\f$ if the
1628 * following conditions hold:
1629 * -# \f$b \in C\f$ and \f$b \neq 0\f$;
1630 * -# \f$a_i\f$ is a positive integer for \f$i = 1, \ldots, r\f$;
1631 * -# the degree of the polynomial \f$p_i\f$ is strictly positive
1632 * for \f$i = 1, \ldots, r\f$;
1633 * -# the polynomial \f$\Pi_{i=1}^r p_i(X)\f$ is square-free.
1635 * Square-free factorizations need not be unique. For example, if
1636 * \f$a_i\f$ is even, we could change the polynomial \f$p_i(X)\f$
1637 * into \f$-p_i(X)\f$.
1638 * Observe also that the factors \f$p_i(X)\f$ need not be irreducible
1641 ex sqrfree(const ex &a, const lst &l)
1643 if (is_exactly_a<numeric>(a) || // algorithm does not trap a==0
1644 is_a<symbol>(a)) // shortcut
1647 // If no lst of variables to factorize in was specified we have to
1648 // invent one now. Maybe one can optimize here by reversing the order
1649 // or so, I don't know.
1653 get_symbol_stats(a, _ex0, sdv);
1654 sym_desc_vec::const_iterator it = sdv.begin(), itend = sdv.end();
1655 while (it != itend) {
1656 args.append(it->sym);
1663 // Find the symbol to factor in at this stage
1664 if (!is_a<symbol>(args.op(0)))
1665 throw (std::runtime_error("sqrfree(): invalid factorization variable"));
1666 const symbol &x = ex_to<symbol>(args.op(0));
1668 // convert the argument from something in Q[X] to something in Z[X]
1669 const numeric lcm = lcm_of_coefficients_denominators(a);
1670 const ex tmp = multiply_lcm(a,lcm);
1673 exvector factors = sqrfree_yun(tmp, x);
1675 // construct the next list of symbols with the first element popped
1677 newargs.remove_first();
1679 // recurse down the factors in remaining variables
1680 if (newargs.nops()>0) {
1681 exvector::iterator i = factors.begin();
1682 while (i != factors.end()) {
1683 *i = sqrfree(*i, newargs);
1688 // Done with recursion, now construct the final result
1690 exvector::const_iterator it = factors.begin(), itend = factors.end();
1691 for (int p = 1; it!=itend; ++it, ++p)
1692 result *= power(*it, p);
1694 // Yun's algorithm does not account for constant factors. (For univariate
1695 // polynomials it works only in the monic case.) We can correct this by
1696 // inserting what has been lost back into the result. For completeness
1697 // we'll also have to recurse down that factor in the remaining variables.
1698 if (newargs.nops()>0)
1699 result *= sqrfree(quo(tmp, result, x), newargs);
1701 result *= quo(tmp, result, x);
1703 // Put in the reational overall factor again and return
1704 return result * lcm.inverse();
1708 /** Compute square-free partial fraction decomposition of rational function
1711 * @param a rational function over Z[x], treated as univariate polynomial
1713 * @param x variable to factor in
1714 * @return decomposed rational function */
1715 ex sqrfree_parfrac(const ex & a, const symbol & x)
1717 // Find numerator and denominator
1718 ex nd = numer_denom(a);
1719 ex numer = nd.op(0), denom = nd.op(1);
1720 //clog << "numer = " << numer << ", denom = " << denom << endl;
1722 // Convert N(x)/D(x) -> Q(x) + R(x)/D(x), so degree(R) < degree(D)
1723 ex red_poly = quo(numer, denom, x), red_numer = rem(numer, denom, x).expand();
1724 //clog << "red_poly = " << red_poly << ", red_numer = " << red_numer << endl;
1726 // Factorize denominator and compute cofactors
1727 exvector yun = sqrfree_yun(denom, x);
1728 //clog << "yun factors: " << exprseq(yun) << endl;
1729 size_t num_yun = yun.size();
1730 exvector factor; factor.reserve(num_yun);
1731 exvector cofac; cofac.reserve(num_yun);
1732 for (size_t i=0; i<num_yun; i++) {
1733 if (!yun[i].is_equal(_ex1)) {
1734 for (size_t j=0; j<=i; j++) {
1735 factor.push_back(pow(yun[i], j+1));
1737 for (size_t k=0; k<num_yun; k++) {
1739 prod *= pow(yun[k], i-j);
1741 prod *= pow(yun[k], k+1);
1743 cofac.push_back(prod.expand());
1747 size_t num_factors = factor.size();
1748 //clog << "factors : " << exprseq(factor) << endl;
1749 //clog << "cofactors: " << exprseq(cofac) << endl;
1751 // Construct coefficient matrix for decomposition
1752 int max_denom_deg = denom.degree(x);
1753 matrix sys(max_denom_deg + 1, num_factors);
1754 matrix rhs(max_denom_deg + 1, 1);
1755 for (int i=0; i<=max_denom_deg; i++) {
1756 for (size_t j=0; j<num_factors; j++)
1757 sys(i, j) = cofac[j].coeff(x, i);
1758 rhs(i, 0) = red_numer.coeff(x, i);
1760 //clog << "coeffs: " << sys << endl;
1761 //clog << "rhs : " << rhs << endl;
1763 // Solve resulting linear system
1764 matrix vars(num_factors, 1);
1765 for (size_t i=0; i<num_factors; i++)
1766 vars(i, 0) = symbol();
1767 matrix sol = sys.solve(vars, rhs);
1769 // Sum up decomposed fractions
1771 for (size_t i=0; i<num_factors; i++)
1772 sum += sol(i, 0) / factor[i];
1774 return red_poly + sum;
1779 * Normal form of rational functions
1783 * Note: The internal normal() functions (= basic::normal() and overloaded
1784 * functions) all return lists of the form {numerator, denominator}. This
1785 * is to get around mul::eval()'s automatic expansion of numeric coefficients.
1786 * E.g. (a+b)/3 is automatically converted to a/3+b/3 but we want to keep
1787 * the information that (a+b) is the numerator and 3 is the denominator.
1791 /** Create a symbol for replacing the expression "e" (or return a previously
1792 * assigned symbol). The symbol and expression are appended to repl, for
1793 * a later application of subs().
1794 * @see ex::normal */
1795 static ex replace_with_symbol(const ex & e, exmap & repl, exmap & rev_lookup)
1797 // Expression already replaced? Then return the assigned symbol
1798 exmap::const_iterator it = rev_lookup.find(e);
1799 if (it != rev_lookup.end())
1802 // Otherwise create new symbol and add to list, taking care that the
1803 // replacement expression doesn't itself contain symbols from repl,
1804 // because subs() is not recursive
1805 ex es = (new symbol)->setflag(status_flags::dynallocated);
1806 ex e_replaced = e.subs(repl, subs_options::no_pattern);
1807 repl.insert(std::make_pair(es, e_replaced));
1808 rev_lookup.insert(std::make_pair(e_replaced, es));
1812 /** Create a symbol for replacing the expression "e" (or return a previously
1813 * assigned symbol). The symbol and expression are appended to repl, and the
1814 * symbol is returned.
1815 * @see basic::to_rational
1816 * @see basic::to_polynomial */
1817 static ex replace_with_symbol(const ex & e, exmap & repl)
1819 // Expression already replaced? Then return the assigned symbol
1820 for (exmap::const_iterator it = repl.begin(); it != repl.end(); ++it)
1821 if (it->second.is_equal(e))
1824 // Otherwise create new symbol and add to list, taking care that the
1825 // replacement expression doesn't itself contain symbols from repl,
1826 // because subs() is not recursive
1827 ex es = (new symbol)->setflag(status_flags::dynallocated);
1828 ex e_replaced = e.subs(repl, subs_options::no_pattern);
1829 repl.insert(std::make_pair(es, e_replaced));
1834 /** Function object to be applied by basic::normal(). */
1835 struct normal_map_function : public map_function {
1837 normal_map_function(int l) : level(l) {}
1838 ex operator()(const ex & e) { return normal(e, level); }
1841 /** Default implementation of ex::normal(). It normalizes the children and
1842 * replaces the object with a temporary symbol.
1843 * @see ex::normal */
1844 ex basic::normal(exmap & repl, exmap & rev_lookup, int level) const
1847 return (new lst(replace_with_symbol(*this, repl, rev_lookup), _ex1))->setflag(status_flags::dynallocated);
1850 return (new lst(replace_with_symbol(*this, repl, rev_lookup), _ex1))->setflag(status_flags::dynallocated);
1851 else if (level == -max_recursion_level)
1852 throw(std::runtime_error("max recursion level reached"));
1854 normal_map_function map_normal(level - 1);
1855 return (new lst(replace_with_symbol(map(map_normal), repl, rev_lookup), _ex1))->setflag(status_flags::dynallocated);
1861 /** Implementation of ex::normal() for symbols. This returns the unmodified symbol.
1862 * @see ex::normal */
1863 ex symbol::normal(exmap & repl, exmap & rev_lookup, int level) const
1865 return (new lst(*this, _ex1))->setflag(status_flags::dynallocated);
1869 /** Implementation of ex::normal() for a numeric. It splits complex numbers
1870 * into re+I*im and replaces I and non-rational real numbers with a temporary
1872 * @see ex::normal */
1873 ex numeric::normal(exmap & repl, exmap & rev_lookup, int level) const
1875 numeric num = numer();
1878 if (num.is_real()) {
1879 if (!num.is_integer())
1880 numex = replace_with_symbol(numex, repl, rev_lookup);
1882 numeric re = num.real(), im = num.imag();
1883 ex re_ex = re.is_rational() ? re : replace_with_symbol(re, repl, rev_lookup);
1884 ex im_ex = im.is_rational() ? im : replace_with_symbol(im, repl, rev_lookup);
1885 numex = re_ex + im_ex * replace_with_symbol(I, repl, rev_lookup);
1888 // Denominator is always a real integer (see numeric::denom())
1889 return (new lst(numex, denom()))->setflag(status_flags::dynallocated);
1893 /** Fraction cancellation.
1894 * @param n numerator
1895 * @param d denominator
1896 * @return cancelled fraction {n, d} as a list */
1897 static ex frac_cancel(const ex &n, const ex &d)
1901 numeric pre_factor = _num1;
1903 //std::clog << "frac_cancel num = " << num << ", den = " << den << std::endl;
1905 // Handle trivial case where denominator is 1
1906 if (den.is_equal(_ex1))
1907 return (new lst(num, den))->setflag(status_flags::dynallocated);
1909 // Handle special cases where numerator or denominator is 0
1911 return (new lst(num, _ex1))->setflag(status_flags::dynallocated);
1912 if (den.expand().is_zero())
1913 throw(std::overflow_error("frac_cancel: division by zero in frac_cancel"));
1915 // Bring numerator and denominator to Z[X] by multiplying with
1916 // LCM of all coefficients' denominators
1917 numeric num_lcm = lcm_of_coefficients_denominators(num);
1918 numeric den_lcm = lcm_of_coefficients_denominators(den);
1919 num = multiply_lcm(num, num_lcm);
1920 den = multiply_lcm(den, den_lcm);
1921 pre_factor = den_lcm / num_lcm;
1923 // Cancel GCD from numerator and denominator
1925 if (gcd(num, den, &cnum, &cden, false) != _ex1) {
1930 // Make denominator unit normal (i.e. coefficient of first symbol
1931 // as defined by get_first_symbol() is made positive)
1932 if (is_exactly_a<numeric>(den)) {
1933 if (ex_to<numeric>(den).is_negative()) {
1939 if (get_first_symbol(den, x)) {
1940 GINAC_ASSERT(is_exactly_a<numeric>(den.unit(x)));
1941 if (ex_to<numeric>(den.unit(x)).is_negative()) {
1948 // Return result as list
1949 //std::clog << " returns num = " << num << ", den = " << den << ", pre_factor = " << pre_factor << std::endl;
1950 return (new lst(num * pre_factor.numer(), den * pre_factor.denom()))->setflag(status_flags::dynallocated);
1954 /** Implementation of ex::normal() for a sum. It expands terms and performs
1955 * fractional addition.
1956 * @see ex::normal */
1957 ex add::normal(exmap & repl, exmap & rev_lookup, int level) const
1960 return (new lst(replace_with_symbol(*this, repl, rev_lookup), _ex1))->setflag(status_flags::dynallocated);
1961 else if (level == -max_recursion_level)
1962 throw(std::runtime_error("max recursion level reached"));
1964 // Normalize children and split each one into numerator and denominator
1965 exvector nums, dens;
1966 nums.reserve(seq.size()+1);
1967 dens.reserve(seq.size()+1);
1968 epvector::const_iterator it = seq.begin(), itend = seq.end();
1969 while (it != itend) {
1970 ex n = ex_to<basic>(recombine_pair_to_ex(*it)).normal(repl, rev_lookup, level-1);
1971 nums.push_back(n.op(0));
1972 dens.push_back(n.op(1));
1975 ex n = ex_to<numeric>(overall_coeff).normal(repl, rev_lookup, level-1);
1976 nums.push_back(n.op(0));
1977 dens.push_back(n.op(1));
1978 GINAC_ASSERT(nums.size() == dens.size());
1980 // Now, nums is a vector of all numerators and dens is a vector of
1982 //std::clog << "add::normal uses " << nums.size() << " summands:\n";
1984 // Add fractions sequentially
1985 exvector::const_iterator num_it = nums.begin(), num_itend = nums.end();
1986 exvector::const_iterator den_it = dens.begin(), den_itend = dens.end();
1987 //std::clog << " num = " << *num_it << ", den = " << *den_it << std::endl;
1988 ex num = *num_it++, den = *den_it++;
1989 while (num_it != num_itend) {
1990 //std::clog << " num = " << *num_it << ", den = " << *den_it << std::endl;
1991 ex next_num = *num_it++, next_den = *den_it++;
1993 // Trivially add sequences of fractions with identical denominators
1994 while ((den_it != den_itend) && next_den.is_equal(*den_it)) {
1995 next_num += *num_it;
1999 // Additiion of two fractions, taking advantage of the fact that
2000 // the heuristic GCD algorithm computes the cofactors at no extra cost
2001 ex co_den1, co_den2;
2002 ex g = gcd(den, next_den, &co_den1, &co_den2, false);
2003 num = ((num * co_den2) + (next_num * co_den1)).expand();
2004 den *= co_den2; // this is the lcm(den, next_den)
2006 //std::clog << " common denominator = " << den << std::endl;
2008 // Cancel common factors from num/den
2009 return frac_cancel(num, den);
2013 /** Implementation of ex::normal() for a product. It cancels common factors
2015 * @see ex::normal() */
2016 ex mul::normal(exmap & repl, exmap & rev_lookup, int level) const
2019 return (new lst(replace_with_symbol(*this, repl, rev_lookup), _ex1))->setflag(status_flags::dynallocated);
2020 else if (level == -max_recursion_level)
2021 throw(std::runtime_error("max recursion level reached"));
2023 // Normalize children, separate into numerator and denominator
2024 exvector num; num.reserve(seq.size());
2025 exvector den; den.reserve(seq.size());
2027 epvector::const_iterator it = seq.begin(), itend = seq.end();
2028 while (it != itend) {
2029 n = ex_to<basic>(recombine_pair_to_ex(*it)).normal(repl, rev_lookup, level-1);
2030 num.push_back(n.op(0));
2031 den.push_back(n.op(1));
2034 n = ex_to<numeric>(overall_coeff).normal(repl, rev_lookup, level-1);
2035 num.push_back(n.op(0));
2036 den.push_back(n.op(1));
2038 // Perform fraction cancellation
2039 return frac_cancel((new mul(num))->setflag(status_flags::dynallocated),
2040 (new mul(den))->setflag(status_flags::dynallocated));
2044 /** Implementation of ex::normal([B) for powers. It normalizes the basis,
2045 * distributes integer exponents to numerator and denominator, and replaces
2046 * non-integer powers by temporary symbols.
2047 * @see ex::normal */
2048 ex power::normal(exmap & repl, exmap & rev_lookup, int level) const
2051 return (new lst(replace_with_symbol(*this, repl, rev_lookup), _ex1))->setflag(status_flags::dynallocated);
2052 else if (level == -max_recursion_level)
2053 throw(std::runtime_error("max recursion level reached"));
2055 // Normalize basis and exponent (exponent gets reassembled)
2056 ex n_basis = ex_to<basic>(basis).normal(repl, rev_lookup, level-1);
2057 ex n_exponent = ex_to<basic>(exponent).normal(repl, rev_lookup, level-1);
2058 n_exponent = n_exponent.op(0) / n_exponent.op(1);
2060 if (n_exponent.info(info_flags::integer)) {
2062 if (n_exponent.info(info_flags::positive)) {
2064 // (a/b)^n -> {a^n, b^n}
2065 return (new lst(power(n_basis.op(0), n_exponent), power(n_basis.op(1), n_exponent)))->setflag(status_flags::dynallocated);
2067 } else if (n_exponent.info(info_flags::negative)) {
2069 // (a/b)^-n -> {b^n, a^n}
2070 return (new lst(power(n_basis.op(1), -n_exponent), power(n_basis.op(0), -n_exponent)))->setflag(status_flags::dynallocated);
2075 if (n_exponent.info(info_flags::positive)) {
2077 // (a/b)^x -> {sym((a/b)^x), 1}
2078 return (new lst(replace_with_symbol(power(n_basis.op(0) / n_basis.op(1), n_exponent), repl, rev_lookup), _ex1))->setflag(status_flags::dynallocated);
2080 } else if (n_exponent.info(info_flags::negative)) {
2082 if (n_basis.op(1).is_equal(_ex1)) {
2084 // a^-x -> {1, sym(a^x)}
2085 return (new lst(_ex1, replace_with_symbol(power(n_basis.op(0), -n_exponent), repl, rev_lookup)))->setflag(status_flags::dynallocated);
2089 // (a/b)^-x -> {sym((b/a)^x), 1}
2090 return (new lst(replace_with_symbol(power(n_basis.op(1) / n_basis.op(0), -n_exponent), repl, rev_lookup), _ex1))->setflag(status_flags::dynallocated);
2095 // (a/b)^x -> {sym((a/b)^x, 1}
2096 return (new lst(replace_with_symbol(power(n_basis.op(0) / n_basis.op(1), n_exponent), repl, rev_lookup), _ex1))->setflag(status_flags::dynallocated);
2100 /** Implementation of ex::normal() for pseries. It normalizes each coefficient
2101 * and replaces the series by a temporary symbol.
2102 * @see ex::normal */
2103 ex pseries::normal(exmap & repl, exmap & rev_lookup, int level) const
2106 epvector::const_iterator i = seq.begin(), end = seq.end();
2108 ex restexp = i->rest.normal();
2109 if (!restexp.is_zero())
2110 newseq.push_back(expair(restexp, i->coeff));
2113 ex n = pseries(relational(var,point), newseq);
2114 return (new lst(replace_with_symbol(n, repl, rev_lookup), _ex1))->setflag(status_flags::dynallocated);
2118 /** Normalization of rational functions.
2119 * This function converts an expression to its normal form
2120 * "numerator/denominator", where numerator and denominator are (relatively
2121 * prime) polynomials. Any subexpressions which are not rational functions
2122 * (like non-rational numbers, non-integer powers or functions like sin(),
2123 * cos() etc.) are replaced by temporary symbols which are re-substituted by
2124 * the (normalized) subexpressions before normal() returns (this way, any
2125 * expression can be treated as a rational function). normal() is applied
2126 * recursively to arguments of functions etc.
2128 * @param level maximum depth of recursion
2129 * @return normalized expression */
2130 ex ex::normal(int level) const
2132 exmap repl, rev_lookup;
2134 ex e = bp->normal(repl, rev_lookup, level);
2135 GINAC_ASSERT(is_a<lst>(e));
2137 // Re-insert replaced symbols
2139 e = e.subs(repl, subs_options::no_pattern);
2141 // Convert {numerator, denominator} form back to fraction
2142 return e.op(0) / e.op(1);
2145 /** Get numerator of an expression. If the expression is not of the normal
2146 * form "numerator/denominator", it is first converted to this form and
2147 * then the numerator is returned.
2150 * @return numerator */
2151 ex ex::numer() const
2153 exmap repl, rev_lookup;
2155 ex e = bp->normal(repl, rev_lookup, 0);
2156 GINAC_ASSERT(is_a<lst>(e));
2158 // Re-insert replaced symbols
2162 return e.op(0).subs(repl, subs_options::no_pattern);
2165 /** Get denominator of an expression. If the expression is not of the normal
2166 * form "numerator/denominator", it is first converted to this form and
2167 * then the denominator is returned.
2170 * @return denominator */
2171 ex ex::denom() const
2173 exmap repl, rev_lookup;
2175 ex e = bp->normal(repl, rev_lookup, 0);
2176 GINAC_ASSERT(is_a<lst>(e));
2178 // Re-insert replaced symbols
2182 return e.op(1).subs(repl, subs_options::no_pattern);
2185 /** Get numerator and denominator of an expression. If the expresison is not
2186 * of the normal form "numerator/denominator", it is first converted to this
2187 * form and then a list [numerator, denominator] is returned.
2190 * @return a list [numerator, denominator] */
2191 ex ex::numer_denom() const
2193 exmap repl, rev_lookup;
2195 ex e = bp->normal(repl, rev_lookup, 0);
2196 GINAC_ASSERT(is_a<lst>(e));
2198 // Re-insert replaced symbols
2202 return e.subs(repl, subs_options::no_pattern);
2206 /** Rationalization of non-rational functions.
2207 * This function converts a general expression to a rational function
2208 * by replacing all non-rational subexpressions (like non-rational numbers,
2209 * non-integer powers or functions like sin(), cos() etc.) to temporary
2210 * symbols. This makes it possible to use functions like gcd() and divide()
2211 * on non-rational functions by applying to_rational() on the arguments,
2212 * calling the desired function and re-substituting the temporary symbols
2213 * in the result. To make the last step possible, all temporary symbols and
2214 * their associated expressions are collected in the map specified by the
2215 * repl parameter, ready to be passed as an argument to ex::subs().
2217 * @param repl collects all temporary symbols and their replacements
2218 * @return rationalized expression */
2219 ex ex::to_rational(exmap & repl) const
2221 return bp->to_rational(repl);
2224 // GiNaC 1.1 compatibility function
2225 ex ex::to_rational(lst & repl_lst) const
2227 // Convert lst to exmap
2229 for (lst::const_iterator it = repl_lst.begin(); it != repl_lst.end(); ++it)
2230 m.insert(std::make_pair(it->op(0), it->op(1)));
2232 ex ret = bp->to_rational(m);
2234 // Convert exmap back to lst
2235 repl_lst.remove_all();
2236 for (exmap::const_iterator it = m.begin(); it != m.end(); ++it)
2237 repl_lst.append(it->first == it->second);
2242 ex ex::to_polynomial(exmap & repl) const
2244 return bp->to_polynomial(repl);
2247 // GiNaC 1.1 compatibility function
2248 ex ex::to_polynomial(lst & repl_lst) const
2250 // Convert lst to exmap
2252 for (lst::const_iterator it = repl_lst.begin(); it != repl_lst.end(); ++it)
2253 m.insert(std::make_pair(it->op(0), it->op(1)));
2255 ex ret = bp->to_polynomial(m);
2257 // Convert exmap back to lst
2258 repl_lst.remove_all();
2259 for (exmap::const_iterator it = m.begin(); it != m.end(); ++it)
2260 repl_lst.append(it->first == it->second);
2265 /** Default implementation of ex::to_rational(). This replaces the object with
2266 * a temporary symbol. */
2267 ex basic::to_rational(exmap & repl) const
2269 return replace_with_symbol(*this, repl);
2272 ex basic::to_polynomial(exmap & repl) const
2274 return replace_with_symbol(*this, repl);
2278 /** Implementation of ex::to_rational() for symbols. This returns the
2279 * unmodified symbol. */
2280 ex symbol::to_rational(exmap & repl) const
2285 /** Implementation of ex::to_polynomial() for symbols. This returns the
2286 * unmodified symbol. */
2287 ex symbol::to_polynomial(exmap & repl) const
2293 /** Implementation of ex::to_rational() for a numeric. It splits complex
2294 * numbers into re+I*im and replaces I and non-rational real numbers with a
2295 * temporary symbol. */
2296 ex numeric::to_rational(exmap & repl) const
2300 return replace_with_symbol(*this, repl);
2302 numeric re = real();
2303 numeric im = imag();
2304 ex re_ex = re.is_rational() ? re : replace_with_symbol(re, repl);
2305 ex im_ex = im.is_rational() ? im : replace_with_symbol(im, repl);
2306 return re_ex + im_ex * replace_with_symbol(I, repl);
2311 /** Implementation of ex::to_polynomial() for a numeric. It splits complex
2312 * numbers into re+I*im and replaces I and non-integer real numbers with a
2313 * temporary symbol. */
2314 ex numeric::to_polynomial(exmap & repl) const
2318 return replace_with_symbol(*this, repl);
2320 numeric re = real();
2321 numeric im = imag();
2322 ex re_ex = re.is_integer() ? re : replace_with_symbol(re, repl);
2323 ex im_ex = im.is_integer() ? im : replace_with_symbol(im, repl);
2324 return re_ex + im_ex * replace_with_symbol(I, repl);
2330 /** Implementation of ex::to_rational() for powers. It replaces non-integer
2331 * powers by temporary symbols. */
2332 ex power::to_rational(exmap & repl) const
2334 if (exponent.info(info_flags::integer))
2335 return power(basis.to_rational(repl), exponent);
2337 return replace_with_symbol(*this, repl);
2340 /** Implementation of ex::to_polynomial() for powers. It replaces non-posint
2341 * powers by temporary symbols. */
2342 ex power::to_polynomial(exmap & repl) const
2344 if (exponent.info(info_flags::posint))
2345 return power(basis.to_rational(repl), exponent);
2347 return replace_with_symbol(*this, repl);
2351 /** Implementation of ex::to_rational() for expairseqs. */
2352 ex expairseq::to_rational(exmap & repl) const
2355 s.reserve(seq.size());
2356 epvector::const_iterator i = seq.begin(), end = seq.end();
2358 s.push_back(split_ex_to_pair(recombine_pair_to_ex(*i).to_rational(repl)));
2361 ex oc = overall_coeff.to_rational(repl);
2362 if (oc.info(info_flags::numeric))
2363 return thisexpairseq(s, overall_coeff);
2365 s.push_back(combine_ex_with_coeff_to_pair(oc, _ex1));
2366 return thisexpairseq(s, default_overall_coeff());
2369 /** Implementation of ex::to_polynomial() for expairseqs. */
2370 ex expairseq::to_polynomial(exmap & repl) const
2373 s.reserve(seq.size());
2374 epvector::const_iterator i = seq.begin(), end = seq.end();
2376 s.push_back(split_ex_to_pair(recombine_pair_to_ex(*i).to_polynomial(repl)));
2379 ex oc = overall_coeff.to_polynomial(repl);
2380 if (oc.info(info_flags::numeric))
2381 return thisexpairseq(s, overall_coeff);
2383 s.push_back(combine_ex_with_coeff_to_pair(oc, _ex1));
2384 return thisexpairseq(s, default_overall_coeff());
2388 /** Remove the common factor in the terms of a sum 'e' by calculating the GCD,
2389 * and multiply it into the expression 'factor' (which needs to be initialized
2390 * to 1, unless you're accumulating factors). */
2391 static ex find_common_factor(const ex & e, ex & factor, exmap & repl)
2393 if (is_exactly_a<add>(e)) {
2395 size_t num = e.nops();
2396 exvector terms; terms.reserve(num);
2399 // Find the common GCD
2400 for (size_t i=0; i<num; i++) {
2401 ex x = e.op(i).to_polynomial(repl);
2403 if (is_exactly_a<add>(x) || is_exactly_a<mul>(x)) {
2405 x = find_common_factor(x, f, repl);
2417 if (gc.is_equal(_ex1))
2420 // The GCD is the factor we pull out
2423 // Now divide all terms by the GCD
2424 for (size_t i=0; i<num; i++) {
2427 // Try to avoid divide() because it expands the polynomial
2429 if (is_exactly_a<mul>(t)) {
2430 for (size_t j=0; j<t.nops(); j++) {
2431 if (t.op(j).is_equal(gc)) {
2432 exvector v; v.reserve(t.nops());
2433 for (size_t k=0; k<t.nops(); k++) {
2437 v.push_back(t.op(k));
2439 t = (new mul(v))->setflag(status_flags::dynallocated);
2449 return (new add(terms))->setflag(status_flags::dynallocated);
2451 } else if (is_exactly_a<mul>(e)) {
2453 size_t num = e.nops();
2454 exvector v; v.reserve(num);
2456 for (size_t i=0; i<num; i++)
2457 v.push_back(find_common_factor(e.op(i), factor, repl));
2459 return (new mul(v))->setflag(status_flags::dynallocated);
2461 } else if (is_exactly_a<power>(e)) {
2463 return e.to_polynomial(repl);
2470 /** Collect common factors in sums. This converts expressions like
2471 * 'a*(b*x+b*y)' to 'a*b*(x+y)'. */
2472 ex collect_common_factors(const ex & e)
2474 if (is_exactly_a<add>(e) || is_exactly_a<mul>(e)) {
2478 ex r = find_common_factor(e, factor, repl);
2479 return factor.subs(repl, subs_options::no_pattern) * r.subs(repl, subs_options::no_pattern);
2486 /** Resultant of two expressions e1,e2 with respect to symbol s.
2487 * Method: Compute determinant of Sylvester matrix of e1,e2,s. */
2488 ex resultant(const ex & e1, const ex & e2, const ex & s)
2490 const ex ee1 = e1.expand();
2491 const ex ee2 = e2.expand();
2492 if (!ee1.info(info_flags::polynomial) ||
2493 !ee2.info(info_flags::polynomial))
2494 throw(std::runtime_error("resultant(): arguments must be polynomials"));
2496 const int h1 = ee1.degree(s);
2497 const int l1 = ee1.ldegree(s);
2498 const int h2 = ee2.degree(s);
2499 const int l2 = ee2.ldegree(s);
2501 const int msize = h1 + h2;
2502 matrix m(msize, msize);
2504 for (int l = h1; l >= l1; --l) {
2505 const ex e = ee1.coeff(s, l);
2506 for (int k = 0; k < h2; ++k)
2509 for (int l = h2; l >= l2; --l) {
2510 const ex e = ee2.coeff(s, l);
2511 for (int k = 0; k < h1; ++k)
2512 m(k+h2, k+h2-l) = e;
2515 return m.determinant();
2519 } // namespace GiNaC