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) 1999-2016 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
31 #include "expairseq.h"
38 #include "relational.h"
39 #include "operators.h"
44 #include "polynomial/chinrem_gcd.h"
51 // If comparing expressions (ex::compare()) is fast, you can set this to 1.
52 // Some routines like quo(), rem() and gcd() will then return a quick answer
53 // when they are called with two identical arguments.
54 #define FAST_COMPARE 1
56 // Set this if you want divide_in_z() to use remembering
57 #define USE_REMEMBER 0
59 // Set this if you want divide_in_z() to use trial division followed by
60 // polynomial interpolation (always slower except for completely dense
62 #define USE_TRIAL_DIVISION 0
64 // Set this to enable some statistical output for the GCD routines
69 // Statistics variables
70 static int gcd_called = 0;
71 static int sr_gcd_called = 0;
72 static int heur_gcd_called = 0;
73 static int heur_gcd_failed = 0;
75 // Print statistics at end of program
76 static struct _stat_print {
79 std::cout << "gcd() called " << gcd_called << " times\n";
80 std::cout << "sr_gcd() called " << sr_gcd_called << " times\n";
81 std::cout << "heur_gcd() called " << heur_gcd_called << " times\n";
82 std::cout << "heur_gcd() failed " << heur_gcd_failed << " times\n";
88 /** Return pointer to first symbol found in expression. Due to GiNaC's
89 * internal ordering of terms, it may not be obvious which symbol this
90 * function returns for a given expression.
92 * @param e expression to search
93 * @param x first symbol found (returned)
94 * @return "false" if no symbol was found, "true" otherwise */
95 static bool get_first_symbol(const ex &e, ex &x)
97 if (is_a<symbol>(e)) {
100 } else if (is_exactly_a<add>(e) || is_exactly_a<mul>(e)) {
101 for (size_t i=0; i<e.nops(); i++)
102 if (get_first_symbol(e.op(i), x))
104 } else if (is_exactly_a<power>(e)) {
105 if (get_first_symbol(e.op(0), x))
113 * Statistical information about symbols in polynomials
116 /** This structure holds information about the highest and lowest degrees
117 * in which a symbol appears in two multivariate polynomials "a" and "b".
118 * A vector of these structures with information about all symbols in
119 * two polynomials can be created with the function get_symbol_stats().
121 * @see get_symbol_stats */
123 /** Initialize symbol, leave other variables uninitialized */
124 sym_desc(const ex& s)
125 : sym(s), deg_a(0), deg_b(0), ldeg_a(0), ldeg_b(0), max_deg(0), max_lcnops(0)
128 /** Reference to symbol */
131 /** Highest degree of symbol in polynomial "a" */
134 /** Highest degree of symbol in polynomial "b" */
137 /** Lowest degree of symbol in polynomial "a" */
140 /** Lowest degree of symbol in polynomial "b" */
143 /** Maximum of deg_a and deg_b (Used for sorting) */
146 /** Maximum number of terms of leading coefficient of symbol in both polynomials */
149 /** Commparison operator for sorting */
150 bool operator<(const sym_desc &x) const
152 if (max_deg == x.max_deg)
153 return max_lcnops < x.max_lcnops;
155 return max_deg < x.max_deg;
159 // Vector of sym_desc structures
160 typedef std::vector<sym_desc> sym_desc_vec;
162 // Add symbol the sym_desc_vec (used internally by get_symbol_stats())
163 static void add_symbol(const ex &s, sym_desc_vec &v)
166 if (it.sym.is_equal(s)) // If it's already in there, don't add it a second time
169 v.push_back(sym_desc(s));
172 // Collect all symbols of an expression (used internally by get_symbol_stats())
173 static void collect_symbols(const ex &e, sym_desc_vec &v)
175 if (is_a<symbol>(e)) {
177 } else if (is_exactly_a<add>(e) || is_exactly_a<mul>(e)) {
178 for (size_t i=0; i<e.nops(); i++)
179 collect_symbols(e.op(i), v);
180 } else if (is_exactly_a<power>(e)) {
181 collect_symbols(e.op(0), v);
185 /** Collect statistical information about symbols in polynomials.
186 * This function fills in a vector of "sym_desc" structs which contain
187 * information about the highest and lowest degrees of all symbols that
188 * appear in two polynomials. The vector is then sorted by minimum
189 * degree (lowest to highest). The information gathered by this
190 * function is used by the GCD routines to identify trivial factors
191 * and to determine which variable to choose as the main variable
192 * for GCD computation.
194 * @param a first multivariate polynomial
195 * @param b second multivariate polynomial
196 * @param v vector of sym_desc structs (filled in) */
197 static void get_symbol_stats(const ex &a, const ex &b, sym_desc_vec &v)
199 collect_symbols(a, v);
200 collect_symbols(b, v);
201 for (auto & it : v) {
202 int deg_a = a.degree(it.sym);
203 int deg_b = b.degree(it.sym);
206 it.max_deg = std::max(deg_a, deg_b);
207 it.max_lcnops = std::max(a.lcoeff(it.sym).nops(), b.lcoeff(it.sym).nops());
208 it.ldeg_a = a.ldegree(it.sym);
209 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)) {
236 numeric c = *_num1_p;
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)) {
241 numeric c = *_num1_p;
242 for (size_t i=0; i<e.nops(); i++)
243 c *= lcmcoeff(e.op(i), *_num1_p);
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_p);
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_p;
277 for (size_t i=0; i<num; i++) {
278 numeric op_lcm = lcmcoeff(e.op(i), *_num1_p);
279 v.push_back(multiply_lcm(e.op(i), op_lcm));
282 v.push_back(lcm / lcm_accum);
283 return dynallocate<mul>(v);
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 dynallocate<add>(v);
290 } else if (is_exactly_a<power>(e)) {
291 if (is_a<symbol>(e.op(0)))
294 numeric root_of_lcm = lcm.power(ex_to<numeric>(e.op(1)).inverse());
295 if (root_of_lcm.is_rational())
296 return pow(multiply_lcm(e.op(0), root_of_lcm), e.op(1));
305 /** Compute the integer content (= GCD of all numeric coefficients) of an
306 * expanded polynomial. For a polynomial with rational coefficients, this
307 * returns g/l where g is the GCD of the coefficients' numerators and l
308 * is the LCM of the coefficients' denominators.
310 * @return integer content */
311 numeric ex::integer_content() const
313 return bp->integer_content();
316 numeric basic::integer_content() const
321 numeric numeric::integer_content() const
326 numeric add::integer_content() const
328 numeric c = *_num0_p, l = *_num1_p;
329 for (auto & it : seq) {
330 GINAC_ASSERT(!is_exactly_a<numeric>(it.rest));
331 GINAC_ASSERT(is_exactly_a<numeric>(it.coeff));
332 c = gcd(ex_to<numeric>(it.coeff).numer(), c);
333 l = lcm(ex_to<numeric>(it.coeff).denom(), l);
335 GINAC_ASSERT(is_exactly_a<numeric>(overall_coeff));
336 c = gcd(ex_to<numeric>(overall_coeff).numer(), c);
337 l = lcm(ex_to<numeric>(overall_coeff).denom(), l);
341 numeric mul::integer_content() const
343 #ifdef DO_GINAC_ASSERT
344 for (auto & it : seq) {
345 GINAC_ASSERT(!is_exactly_a<numeric>(recombine_pair_to_ex(it)));
347 #endif // def DO_GINAC_ASSERT
348 GINAC_ASSERT(is_exactly_a<numeric>(overall_coeff));
349 return abs(ex_to<numeric>(overall_coeff));
354 * Polynomial quotients and remainders
357 /** Quotient q(x) of polynomials a(x) and b(x) in Q[x].
358 * It satisfies a(x)=b(x)*q(x)+r(x).
360 * @param a first polynomial in x (dividend)
361 * @param b second polynomial in x (divisor)
362 * @param x a and b are polynomials in x
363 * @param check_args check whether a and b are polynomials with rational
364 * coefficients (defaults to "true")
365 * @return quotient of a and b in Q[x] */
366 ex quo(const ex &a, const ex &b, const ex &x, bool check_args)
369 throw(std::overflow_error("quo: division by zero"));
370 if (is_exactly_a<numeric>(a) && is_exactly_a<numeric>(b))
376 if (check_args && (!a.info(info_flags::rational_polynomial) || !b.info(info_flags::rational_polynomial)))
377 throw(std::invalid_argument("quo: arguments must be polynomials over the rationals"));
379 // Polynomial long division
383 int bdeg = b.degree(x);
384 int rdeg = r.degree(x);
385 ex blcoeff = b.expand().coeff(x, bdeg);
386 bool blcoeff_is_numeric = is_exactly_a<numeric>(blcoeff);
387 exvector v; v.reserve(std::max(rdeg - bdeg + 1, 0));
388 while (rdeg >= bdeg) {
389 ex term, rcoeff = r.coeff(x, rdeg);
390 if (blcoeff_is_numeric)
391 term = rcoeff / blcoeff;
393 if (!divide(rcoeff, blcoeff, term, false))
394 return dynallocate<fail>();
396 term *= pow(x, rdeg - bdeg);
398 r -= (term * b).expand();
403 return dynallocate<add>(v);
407 /** Remainder r(x) of polynomials a(x) and b(x) in Q[x].
408 * It satisfies a(x)=b(x)*q(x)+r(x).
410 * @param a first polynomial in x (dividend)
411 * @param b second polynomial in x (divisor)
412 * @param x a and b are polynomials in x
413 * @param check_args check whether a and b are polynomials with rational
414 * coefficients (defaults to "true")
415 * @return remainder of a(x) and b(x) in Q[x] */
416 ex rem(const ex &a, const ex &b, const ex &x, bool check_args)
419 throw(std::overflow_error("rem: division by zero"));
420 if (is_exactly_a<numeric>(a)) {
421 if (is_exactly_a<numeric>(b))
430 if (check_args && (!a.info(info_flags::rational_polynomial) || !b.info(info_flags::rational_polynomial)))
431 throw(std::invalid_argument("rem: arguments must be polynomials over the rationals"));
433 // Polynomial long division
437 int bdeg = b.degree(x);
438 int rdeg = r.degree(x);
439 ex blcoeff = b.expand().coeff(x, bdeg);
440 bool blcoeff_is_numeric = is_exactly_a<numeric>(blcoeff);
441 while (rdeg >= bdeg) {
442 ex term, rcoeff = r.coeff(x, rdeg);
443 if (blcoeff_is_numeric)
444 term = rcoeff / blcoeff;
446 if (!divide(rcoeff, blcoeff, term, false))
447 return dynallocate<fail>();
449 term *= pow(x, rdeg - bdeg);
450 r -= (term * b).expand();
459 /** Decompose rational function a(x)=N(x)/D(x) into P(x)+n(x)/D(x)
460 * with degree(n, x) < degree(D, x).
462 * @param a rational function in x
463 * @param x a is a function of x
464 * @return decomposed function. */
465 ex decomp_rational(const ex &a, const ex &x)
467 ex nd = numer_denom(a);
468 ex numer = nd.op(0), denom = nd.op(1);
469 ex q = quo(numer, denom, x);
470 if (is_exactly_a<fail>(q))
473 return q + rem(numer, denom, x) / denom;
477 /** Pseudo-remainder of polynomials a(x) and b(x) in Q[x].
479 * @param a first polynomial in x (dividend)
480 * @param b second polynomial in x (divisor)
481 * @param x a and b are polynomials in x
482 * @param check_args check whether a and b are polynomials with rational
483 * coefficients (defaults to "true")
484 * @return pseudo-remainder of a(x) and b(x) in Q[x] */
485 ex prem(const ex &a, const ex &b, const ex &x, bool check_args)
488 throw(std::overflow_error("prem: division by zero"));
489 if (is_exactly_a<numeric>(a)) {
490 if (is_exactly_a<numeric>(b))
495 if (check_args && (!a.info(info_flags::rational_polynomial) || !b.info(info_flags::rational_polynomial)))
496 throw(std::invalid_argument("prem: arguments must be polynomials over the rationals"));
498 // Polynomial long division
501 int rdeg = r.degree(x);
502 int bdeg = eb.degree(x);
505 blcoeff = eb.coeff(x, bdeg);
509 eb -= blcoeff * pow(x, bdeg);
513 int delta = rdeg - bdeg + 1, i = 0;
514 while (rdeg >= bdeg && !r.is_zero()) {
515 ex rlcoeff = r.coeff(x, rdeg);
516 ex term = (pow(x, rdeg - bdeg) * eb * rlcoeff).expand();
520 r -= rlcoeff * pow(x, rdeg);
521 r = (blcoeff * r).expand() - term;
525 return pow(blcoeff, delta - i) * r;
529 /** Sparse pseudo-remainder of polynomials a(x) and b(x) in Q[x].
531 * @param a first polynomial in x (dividend)
532 * @param b second polynomial in x (divisor)
533 * @param x a and b are polynomials in x
534 * @param check_args check whether a and b are polynomials with rational
535 * coefficients (defaults to "true")
536 * @return sparse pseudo-remainder of a(x) and b(x) in Q[x] */
537 ex sprem(const ex &a, const ex &b, const ex &x, bool check_args)
540 throw(std::overflow_error("prem: division by zero"));
541 if (is_exactly_a<numeric>(a)) {
542 if (is_exactly_a<numeric>(b))
547 if (check_args && (!a.info(info_flags::rational_polynomial) || !b.info(info_flags::rational_polynomial)))
548 throw(std::invalid_argument("prem: arguments must be polynomials over the rationals"));
550 // Polynomial long division
553 int rdeg = r.degree(x);
554 int bdeg = eb.degree(x);
557 blcoeff = eb.coeff(x, bdeg);
561 eb -= blcoeff * pow(x, bdeg);
565 while (rdeg >= bdeg && !r.is_zero()) {
566 ex rlcoeff = r.coeff(x, rdeg);
567 ex term = (pow(x, rdeg - bdeg) * eb * rlcoeff).expand();
571 r -= rlcoeff * pow(x, rdeg);
572 r = (blcoeff * r).expand() - term;
579 /** Exact polynomial division of a(X) by b(X) in Q[X].
581 * @param a first multivariate polynomial (dividend)
582 * @param b second multivariate polynomial (divisor)
583 * @param q quotient (returned)
584 * @param check_args check whether a and b are polynomials with rational
585 * coefficients (defaults to "true")
586 * @return "true" when exact division succeeds (quotient returned in q),
587 * "false" otherwise (q left untouched) */
588 bool divide(const ex &a, const ex &b, ex &q, bool check_args)
591 throw(std::overflow_error("divide: division by zero"));
596 if (is_exactly_a<numeric>(b)) {
599 } else if (is_exactly_a<numeric>(a))
607 if (check_args && (!a.info(info_flags::rational_polynomial) ||
608 !b.info(info_flags::rational_polynomial)))
609 throw(std::invalid_argument("divide: arguments must be polynomials over the rationals"));
613 if (!get_first_symbol(a, x) && !get_first_symbol(b, x))
614 throw(std::invalid_argument("invalid expression in divide()"));
616 // Try to avoid expanding partially factored expressions.
617 if (is_exactly_a<mul>(b)) {
618 // Divide sequentially by each term
619 ex rem_new, rem_old = a;
620 for (size_t i=0; i < b.nops(); i++) {
621 if (! divide(rem_old, b.op(i), rem_new, false))
627 } else if (is_exactly_a<power>(b)) {
628 const ex& bb(b.op(0));
629 int exp_b = ex_to<numeric>(b.op(1)).to_int();
630 ex rem_new, rem_old = a;
631 for (int i=exp_b; i>0; i--) {
632 if (! divide(rem_old, bb, rem_new, false))
640 if (is_exactly_a<mul>(a)) {
641 // Divide sequentially each term. If some term in a is divisible
642 // by b we are done... and if not, we can't really say anything.
645 bool divisible_p = false;
646 for (i=0; i < a.nops(); ++i) {
647 if (divide(a.op(i), b, rem_i, false)) {
654 resv.reserve(a.nops());
655 for (size_t j=0; j < a.nops(); j++) {
657 resv.push_back(rem_i);
659 resv.push_back(a.op(j));
661 q = dynallocate<mul>(resv);
664 } else if (is_exactly_a<power>(a)) {
665 // The base itself might be divisible by b, in that case we don't
667 const ex& ab(a.op(0));
668 int a_exp = ex_to<numeric>(a.op(1)).to_int();
670 if (divide(ab, b, rem_i, false)) {
671 q = rem_i * pow(ab, a_exp - 1);
674 // code below is commented-out because it leads to a significant slowdown
675 // for (int i=2; i < a_exp; i++) {
676 // if (divide(power(ab, i), b, rem_i, false)) {
677 // q = rem_i*power(ab, a_exp - i);
680 // } // ... so we *really* need to expand expression.
683 // Polynomial long division (recursive)
689 int bdeg = b.degree(x);
690 int rdeg = r.degree(x);
691 ex blcoeff = b.expand().coeff(x, bdeg);
692 bool blcoeff_is_numeric = is_exactly_a<numeric>(blcoeff);
693 exvector v; v.reserve(std::max(rdeg - bdeg + 1, 0));
694 while (rdeg >= bdeg) {
695 ex term, rcoeff = r.coeff(x, rdeg);
696 if (blcoeff_is_numeric)
697 term = rcoeff / blcoeff;
699 if (!divide(rcoeff, blcoeff, term, false))
701 term *= pow(x, rdeg - bdeg);
703 r -= (term * b).expand();
705 q = dynallocate<add>(v);
719 typedef std::pair<ex, ex> ex2;
720 typedef std::pair<ex, bool> exbool;
723 bool operator() (const ex2 &p, const ex2 &q) const
725 int cmp = p.first.compare(q.first);
726 return ((cmp<0) || (!(cmp>0) && p.second.compare(q.second)<0));
730 typedef std::map<ex2, exbool, ex2_less> ex2_exbool_remember;
734 /** Exact polynomial division of a(X) by b(X) in Z[X].
735 * This functions works like divide() but the input and output polynomials are
736 * in Z[X] instead of Q[X] (i.e. they have integer coefficients). Unlike
737 * divide(), it doesn't check whether the input polynomials really are integer
738 * polynomials, so be careful of what you pass in. Also, you have to run
739 * get_symbol_stats() over the input polynomials before calling this function
740 * and pass an iterator to the first element of the sym_desc vector. This
741 * function is used internally by the heur_gcd().
743 * @param a first multivariate polynomial (dividend)
744 * @param b second multivariate polynomial (divisor)
745 * @param q quotient (returned)
746 * @param var iterator to first element of vector of sym_desc structs
747 * @return "true" when exact division succeeds (the quotient is returned in
748 * q), "false" otherwise.
749 * @see get_symbol_stats, heur_gcd */
750 static bool divide_in_z(const ex &a, const ex &b, ex &q, sym_desc_vec::const_iterator var)
754 throw(std::overflow_error("divide_in_z: division by zero"));
755 if (b.is_equal(_ex1)) {
759 if (is_exactly_a<numeric>(a)) {
760 if (is_exactly_a<numeric>(b)) {
762 return q.info(info_flags::integer);
775 static ex2_exbool_remember dr_remember;
776 ex2_exbool_remember::const_iterator remembered = dr_remember.find(ex2(a, b));
777 if (remembered != dr_remember.end()) {
778 q = remembered->second.first;
779 return remembered->second.second;
783 if (is_exactly_a<power>(b)) {
784 const ex& bb(b.op(0));
786 int exp_b = ex_to<numeric>(b.op(1)).to_int();
787 for (int i=exp_b; i>0; i--) {
788 if (!divide_in_z(qbar, bb, q, var))
795 if (is_exactly_a<mul>(b)) {
797 for (const auto & it : b) {
798 sym_desc_vec sym_stats;
799 get_symbol_stats(a, it, sym_stats);
800 if (!divide_in_z(qbar, it, q, sym_stats.begin()))
809 const ex &x = var->sym;
812 int adeg = a.degree(x), bdeg = b.degree(x);
816 #if USE_TRIAL_DIVISION
818 // Trial division with polynomial interpolation
821 // Compute values at evaluation points 0..adeg
822 vector<numeric> alpha; alpha.reserve(adeg + 1);
823 exvector u; u.reserve(adeg + 1);
824 numeric point = *_num0_p;
826 for (i=0; i<=adeg; i++) {
827 ex bs = b.subs(x == point, subs_options::no_pattern);
828 while (bs.is_zero()) {
830 bs = b.subs(x == point, subs_options::no_pattern);
832 if (!divide_in_z(a.subs(x == point, subs_options::no_pattern), bs, c, var+1))
834 alpha.push_back(point);
840 vector<numeric> rcp; rcp.reserve(adeg + 1);
841 rcp.push_back(*_num0_p);
842 for (k=1; k<=adeg; k++) {
843 numeric product = alpha[k] - alpha[0];
845 product *= alpha[k] - alpha[i];
846 rcp.push_back(product.inverse());
849 // Compute Newton coefficients
850 exvector v; v.reserve(adeg + 1);
852 for (k=1; k<=adeg; k++) {
854 for (i=k-2; i>=0; i--)
855 temp = temp * (alpha[k] - alpha[i]) + v[i];
856 v.push_back((u[k] - temp) * rcp[k]);
859 // Convert from Newton form to standard form
861 for (k=adeg-1; k>=0; k--)
862 c = c * (x - alpha[k]) + v[k];
864 if (c.degree(x) == (adeg - bdeg)) {
872 // Polynomial long division (recursive)
878 ex blcoeff = eb.coeff(x, bdeg);
879 exvector v; v.reserve(std::max(rdeg - bdeg + 1, 0));
880 while (rdeg >= bdeg) {
881 ex term, rcoeff = r.coeff(x, rdeg);
882 if (!divide_in_z(rcoeff, blcoeff, term, var+1))
884 term = (term * pow(x, rdeg - bdeg)).expand();
886 r -= (term * eb).expand();
888 q = dynallocate<add>(v);
890 dr_remember[ex2(a, b)] = exbool(q, true);
897 dr_remember[ex2(a, b)] = exbool(q, false);
906 * Separation of unit part, content part and primitive part of polynomials
909 /** Compute unit part (= sign of leading coefficient) of a multivariate
910 * polynomial in Q[x]. The product of unit part, content part, and primitive
911 * part is the polynomial itself.
913 * @param x main variable
915 * @see ex::content, ex::primpart, ex::unitcontprim */
916 ex ex::unit(const ex &x) const
918 ex c = expand().lcoeff(x);
919 if (is_exactly_a<numeric>(c))
920 return c.info(info_flags::negative) ?_ex_1 : _ex1;
923 if (get_first_symbol(c, y))
926 throw(std::invalid_argument("invalid expression in unit()"));
931 /** Compute content part (= unit normal GCD of all coefficients) of a
932 * multivariate polynomial in Q[x]. The product of unit part, content part,
933 * and primitive part is the polynomial itself.
935 * @param x main variable
936 * @return content part
937 * @see ex::unit, ex::primpart, ex::unitcontprim */
938 ex ex::content(const ex &x) const
940 if (is_exactly_a<numeric>(*this))
941 return info(info_flags::negative) ? -*this : *this;
947 // First, divide out the integer content (which we can calculate very efficiently).
948 // If the leading coefficient of the quotient is an integer, we are done.
949 ex c = e.integer_content();
951 int deg = r.degree(x);
952 ex lcoeff = r.coeff(x, deg);
953 if (lcoeff.info(info_flags::integer))
956 // GCD of all coefficients
957 int ldeg = r.ldegree(x);
959 return lcoeff * c / lcoeff.unit(x);
961 for (int i=ldeg; i<=deg; i++)
962 cont = gcd(r.coeff(x, i), cont, nullptr, nullptr, false);
967 /** Compute primitive part of a multivariate polynomial in Q[x]. The result
968 * will be a unit-normal polynomial with a content part of 1. The product
969 * of unit part, content part, and primitive part is the polynomial itself.
971 * @param x main variable
972 * @return primitive part
973 * @see ex::unit, ex::content, ex::unitcontprim */
974 ex ex::primpart(const ex &x) const
976 // We need to compute the unit and content anyway, so call unitcontprim()
978 unitcontprim(x, u, c, p);
983 /** Compute primitive part of a multivariate polynomial in Q[x] when the
984 * content part is already known. This function is faster in computing the
985 * primitive part than the previous function.
987 * @param x main variable
988 * @param c previously computed content part
989 * @return primitive part */
990 ex ex::primpart(const ex &x, const ex &c) const
992 if (is_zero() || c.is_zero())
994 if (is_exactly_a<numeric>(*this))
997 // Divide by unit and content to get primitive part
999 if (is_exactly_a<numeric>(c))
1000 return *this / (c * u);
1002 return quo(*this, c * u, x, false);
1006 /** Compute unit part, content part, and primitive part of a multivariate
1007 * polynomial in Q[x]. The product of the three parts is the polynomial
1010 * @param x main variable
1011 * @param u unit part (returned)
1012 * @param c content part (returned)
1013 * @param p primitive part (returned)
1014 * @see ex::unit, ex::content, ex::primpart */
1015 void ex::unitcontprim(const ex &x, ex &u, ex &c, ex &p) const
1017 // Quick check for zero (avoid expanding)
1024 // Special case: input is a number
1025 if (is_exactly_a<numeric>(*this)) {
1026 if (info(info_flags::negative)) {
1028 c = abs(ex_to<numeric>(*this));
1037 // Expand input polynomial
1045 // Compute unit and content
1049 // Divide by unit and content to get primitive part
1054 if (is_exactly_a<numeric>(c))
1055 p = *this / (c * u);
1057 p = quo(e, c * u, x, false);
1062 * GCD of multivariate polynomials
1065 /** Compute GCD of multivariate polynomials using the subresultant PRS
1066 * algorithm. This function is used internally by gcd().
1068 * @param a first multivariate polynomial
1069 * @param b second multivariate polynomial
1070 * @param var iterator to first element of vector of sym_desc structs
1071 * @return the GCD as a new expression
1074 static ex sr_gcd(const ex &a, const ex &b, sym_desc_vec::const_iterator var)
1080 // The first symbol is our main variable
1081 const ex &x = var->sym;
1083 // Sort c and d so that c has higher degree
1085 int adeg = a.degree(x), bdeg = b.degree(x);
1099 // Remove content from c and d, to be attached to GCD later
1100 ex cont_c = c.content(x);
1101 ex cont_d = d.content(x);
1102 ex gamma = gcd(cont_c, cont_d, nullptr, nullptr, false);
1105 c = c.primpart(x, cont_c);
1106 d = d.primpart(x, cont_d);
1108 // First element of subresultant sequence
1109 ex r = _ex0, ri = _ex1, psi = _ex1;
1110 int delta = cdeg - ddeg;
1114 // Calculate polynomial pseudo-remainder
1115 r = prem(c, d, x, false);
1117 return gamma * d.primpart(x);
1121 if (!divide_in_z(r, ri * pow(psi, delta), d, var))
1122 throw(std::runtime_error("invalid expression in sr_gcd(), division failed"));
1125 if (is_exactly_a<numeric>(r))
1128 return gamma * r.primpart(x);
1131 // Next element of subresultant sequence
1132 ri = c.expand().lcoeff(x);
1136 divide_in_z(pow(ri, delta), pow(psi, delta-1), psi, var+1);
1137 delta = cdeg - ddeg;
1142 /** Return maximum (absolute value) coefficient of a polynomial.
1143 * This function is used internally by heur_gcd().
1145 * @return maximum coefficient
1147 numeric ex::max_coefficient() const
1149 return bp->max_coefficient();
1152 /** Implementation ex::max_coefficient().
1154 numeric basic::max_coefficient() const
1159 numeric numeric::max_coefficient() const
1164 numeric add::max_coefficient() const
1166 GINAC_ASSERT(is_exactly_a<numeric>(overall_coeff));
1167 numeric cur_max = abs(ex_to<numeric>(overall_coeff));
1168 for (auto & it : seq) {
1170 GINAC_ASSERT(!is_exactly_a<numeric>(it.rest));
1171 a = abs(ex_to<numeric>(it.coeff));
1178 numeric mul::max_coefficient() const
1180 #ifdef DO_GINAC_ASSERT
1181 for (auto & it : seq) {
1182 GINAC_ASSERT(!is_exactly_a<numeric>(recombine_pair_to_ex(it)));
1184 #endif // def DO_GINAC_ASSERT
1185 GINAC_ASSERT(is_exactly_a<numeric>(overall_coeff));
1186 return abs(ex_to<numeric>(overall_coeff));
1190 /** Apply symmetric modular homomorphism to an expanded multivariate
1191 * polynomial. This function is usually used internally by heur_gcd().
1194 * @return mapped polynomial
1196 ex basic::smod(const numeric &xi) const
1201 ex numeric::smod(const numeric &xi) const
1203 return GiNaC::smod(*this, xi);
1206 ex add::smod(const numeric &xi) const
1209 newseq.reserve(seq.size()+1);
1210 for (auto & it : seq) {
1211 GINAC_ASSERT(!is_exactly_a<numeric>(it.rest));
1212 numeric coeff = GiNaC::smod(ex_to<numeric>(it.coeff), xi);
1213 if (!coeff.is_zero())
1214 newseq.push_back(expair(it.rest, coeff));
1216 GINAC_ASSERT(is_exactly_a<numeric>(overall_coeff));
1217 numeric coeff = GiNaC::smod(ex_to<numeric>(overall_coeff), xi);
1218 return dynallocate<add>(std::move(newseq), coeff);
1221 ex mul::smod(const numeric &xi) const
1223 #ifdef DO_GINAC_ASSERT
1224 for (auto & it : seq) {
1225 GINAC_ASSERT(!is_exactly_a<numeric>(recombine_pair_to_ex(it)));
1227 #endif // def DO_GINAC_ASSERT
1228 mul & mulcopy = dynallocate<mul>(*this);
1229 GINAC_ASSERT(is_exactly_a<numeric>(overall_coeff));
1230 mulcopy.overall_coeff = GiNaC::smod(ex_to<numeric>(overall_coeff),xi);
1231 mulcopy.clearflag(status_flags::evaluated);
1232 mulcopy.clearflag(status_flags::hash_calculated);
1237 /** xi-adic polynomial interpolation */
1238 static ex interpolate(const ex &gamma, const numeric &xi, const ex &x, int degree_hint = 1)
1240 exvector g; g.reserve(degree_hint);
1242 numeric rxi = xi.inverse();
1243 for (int i=0; !e.is_zero(); i++) {
1245 g.push_back(gi * pow(x, i));
1248 return dynallocate<add>(g);
1251 /** Exception thrown by heur_gcd() to signal failure. */
1252 class gcdheu_failed {};
1254 /** Compute GCD of multivariate polynomials using the heuristic GCD algorithm.
1255 * get_symbol_stats() must have been called previously with the input
1256 * polynomials and an iterator to the first element of the sym_desc vector
1257 * passed in. This function is used internally by gcd().
1259 * @param a first integer multivariate polynomial (expanded)
1260 * @param b second integer multivariate polynomial (expanded)
1261 * @param ca cofactor of polynomial a (returned), nullptr to suppress
1262 * calculation of cofactor
1263 * @param cb cofactor of polynomial b (returned), nullptr to suppress
1264 * calculation of cofactor
1265 * @param var iterator to first element of vector of sym_desc structs
1266 * @param res the GCD (returned)
1267 * @return true if GCD was computed, false otherwise.
1269 * @exception gcdheu_failed() */
1270 static bool heur_gcd_z(ex& res, const ex &a, const ex &b, ex *ca, ex *cb,
1271 sym_desc_vec::const_iterator var)
1277 // Algorithm only works for non-vanishing input polynomials
1278 if (a.is_zero() || b.is_zero())
1281 // GCD of two numeric values -> CLN
1282 if (is_exactly_a<numeric>(a) && is_exactly_a<numeric>(b)) {
1283 numeric g = gcd(ex_to<numeric>(a), ex_to<numeric>(b));
1285 *ca = ex_to<numeric>(a) / g;
1287 *cb = ex_to<numeric>(b) / g;
1292 // The first symbol is our main variable
1293 const ex &x = var->sym;
1295 // Remove integer content
1296 numeric gc = gcd(a.integer_content(), b.integer_content());
1297 numeric rgc = gc.inverse();
1300 int maxdeg = std::max(p.degree(x), q.degree(x));
1302 // Find evaluation point
1303 numeric mp = p.max_coefficient();
1304 numeric mq = q.max_coefficient();
1307 xi = mq * (*_num2_p) + (*_num2_p);
1309 xi = mp * (*_num2_p) + (*_num2_p);
1312 for (int t=0; t<6; t++) {
1313 if (xi.int_length() * maxdeg > 100000) {
1314 throw gcdheu_failed();
1317 // Apply evaluation homomorphism and calculate GCD
1320 bool found = heur_gcd_z(gamma,
1321 p.subs(x == xi, subs_options::no_pattern),
1322 q.subs(x == xi, subs_options::no_pattern),
1325 gamma = gamma.expand();
1326 // Reconstruct polynomial from GCD of mapped polynomials
1327 ex g = interpolate(gamma, xi, x, maxdeg);
1329 // Remove integer content
1330 g /= g.integer_content();
1332 // If the calculated polynomial divides both p and q, this is the GCD
1334 if (divide_in_z(p, g, ca ? *ca : dummy, var) && divide_in_z(q, g, cb ? *cb : dummy, var)) {
1341 // Next evaluation point
1342 xi = iquo(xi * isqrt(isqrt(xi)) * numeric(73794), numeric(27011));
1347 /** Compute GCD of multivariate polynomials using the heuristic GCD algorithm.
1348 * get_symbol_stats() must have been called previously with the input
1349 * polynomials and an iterator to the first element of the sym_desc vector
1350 * passed in. This function is used internally by gcd().
1352 * @param a first rational multivariate polynomial (expanded)
1353 * @param b second rational multivariate polynomial (expanded)
1354 * @param ca cofactor of polynomial a (returned), nullptr to suppress
1355 * calculation of cofactor
1356 * @param cb cofactor of polynomial b (returned), nullptr to suppress
1357 * calculation of cofactor
1358 * @param var iterator to first element of vector of sym_desc structs
1359 * @param res the GCD (returned)
1360 * @return true if GCD was computed, false otherwise.
1364 static bool heur_gcd(ex& res, const ex& a, const ex& b, ex *ca, ex *cb,
1365 sym_desc_vec::const_iterator var)
1367 if (a.info(info_flags::integer_polynomial) &&
1368 b.info(info_flags::integer_polynomial)) {
1370 return heur_gcd_z(res, a, b, ca, cb, var);
1371 } catch (gcdheu_failed) {
1376 // convert polynomials to Z[X]
1377 const numeric a_lcm = lcm_of_coefficients_denominators(a);
1378 const numeric ab_lcm = lcmcoeff(b, a_lcm);
1380 const ex ai = a*ab_lcm;
1381 const ex bi = b*ab_lcm;
1382 if (!ai.info(info_flags::integer_polynomial))
1383 throw std::logic_error("heur_gcd: not an integer polynomial [1]");
1385 if (!bi.info(info_flags::integer_polynomial))
1386 throw std::logic_error("heur_gcd: not an integer polynomial [2]");
1390 found = heur_gcd_z(res, ai, bi, ca, cb, var);
1391 } catch (gcdheu_failed) {
1395 // GCD is not unique, it's defined up to a unit (i.e. invertible
1396 // element). If the coefficient ring is a field, every its element is
1397 // invertible, so one can multiply the polynomial GCD with any element
1398 // of the coefficient field. We use this ambiguity to make cofactors
1399 // integer polynomials.
1406 // gcd helper to handle partially factored polynomials (to avoid expanding
1407 // large expressions). At least one of the arguments should be a power.
1408 static ex gcd_pf_pow(const ex& a, const ex& b, ex* ca, ex* cb);
1410 // gcd helper to handle partially factored polynomials (to avoid expanding
1411 // large expressions). At least one of the arguments should be a product.
1412 static ex gcd_pf_mul(const ex& a, const ex& b, ex* ca, ex* cb);
1414 /** Compute GCD (Greatest Common Divisor) of multivariate polynomials a(X)
1415 * and b(X) in Z[X]. Optionally also compute the cofactors of a and b,
1416 * defined by a = ca * gcd(a, b) and b = cb * gcd(a, b).
1418 * @param a first multivariate polynomial
1419 * @param b second multivariate polynomial
1420 * @param ca pointer to expression that will receive the cofactor of a, or nullptr
1421 * @param cb pointer to expression that will receive the cofactor of b, or nullptr
1422 * @param check_args check whether a and b are polynomials with rational
1423 * coefficients (defaults to "true")
1424 * @return the GCD as a new expression */
1425 ex gcd(const ex &a, const ex &b, ex *ca, ex *cb, bool check_args, unsigned options)
1431 // GCD of numerics -> CLN
1432 if (is_exactly_a<numeric>(a) && is_exactly_a<numeric>(b)) {
1433 numeric g = gcd(ex_to<numeric>(a), ex_to<numeric>(b));
1442 *ca = ex_to<numeric>(a) / g;
1444 *cb = ex_to<numeric>(b) / g;
1451 if (check_args && (!a.info(info_flags::rational_polynomial) || !b.info(info_flags::rational_polynomial))) {
1452 throw(std::invalid_argument("gcd: arguments must be polynomials over the rationals"));
1455 // Partially factored cases (to avoid expanding large expressions)
1456 if (!(options & gcd_options::no_part_factored)) {
1457 if (is_exactly_a<mul>(a) || is_exactly_a<mul>(b))
1458 return gcd_pf_mul(a, b, ca, cb);
1460 if (is_exactly_a<power>(a) || is_exactly_a<power>(b))
1461 return gcd_pf_pow(a, b, ca, cb);
1465 // Some trivial cases
1466 ex aex = a.expand(), bex = b.expand();
1467 if (aex.is_zero()) {
1474 if (bex.is_zero()) {
1481 if (aex.is_equal(_ex1) || bex.is_equal(_ex1)) {
1489 if (a.is_equal(b)) {
1498 if (is_a<symbol>(aex)) {
1499 if (! bex.subs(aex==_ex0, subs_options::no_pattern).is_zero()) {
1508 if (is_a<symbol>(bex)) {
1509 if (! aex.subs(bex==_ex0, subs_options::no_pattern).is_zero()) {
1518 if (is_exactly_a<numeric>(aex)) {
1519 numeric bcont = bex.integer_content();
1520 numeric g = gcd(ex_to<numeric>(aex), bcont);
1522 *ca = ex_to<numeric>(aex)/g;
1528 if (is_exactly_a<numeric>(bex)) {
1529 numeric acont = aex.integer_content();
1530 numeric g = gcd(ex_to<numeric>(bex), acont);
1534 *cb = ex_to<numeric>(bex)/g;
1538 // Gather symbol statistics
1539 sym_desc_vec sym_stats;
1540 get_symbol_stats(a, b, sym_stats);
1542 // The symbol with least degree which is contained in both polynomials
1543 // is our main variable
1544 sym_desc_vec::iterator vari = sym_stats.begin();
1545 while ((vari != sym_stats.end()) &&
1546 (((vari->ldeg_b == 0) && (vari->deg_b == 0)) ||
1547 ((vari->ldeg_a == 0) && (vari->deg_a == 0))))
1550 // No common symbols at all, just return 1:
1551 if (vari == sym_stats.end()) {
1552 // N.B: keep cofactors factored
1559 // move symbols which contained only in one of the polynomials
1561 rotate(sym_stats.begin(), vari, sym_stats.end());
1563 sym_desc_vec::const_iterator var = sym_stats.begin();
1564 const ex &x = var->sym;
1566 // Cancel trivial common factor
1567 int ldeg_a = var->ldeg_a;
1568 int ldeg_b = var->ldeg_b;
1569 int min_ldeg = std::min(ldeg_a,ldeg_b);
1571 ex common = pow(x, min_ldeg);
1572 return gcd((aex / common).expand(), (bex / common).expand(), ca, cb, false) * common;
1575 // Try to eliminate variables
1576 if (var->deg_a == 0 && var->deg_b != 0 ) {
1577 ex bex_u, bex_c, bex_p;
1578 bex.unitcontprim(x, bex_u, bex_c, bex_p);
1579 ex g = gcd(aex, bex_c, ca, cb, false);
1581 *cb *= bex_u * bex_p;
1583 } else if (var->deg_b == 0 && var->deg_a != 0) {
1584 ex aex_u, aex_c, aex_p;
1585 aex.unitcontprim(x, aex_u, aex_c, aex_p);
1586 ex g = gcd(aex_c, bex, ca, cb, false);
1588 *ca *= aex_u * aex_p;
1592 // Try heuristic algorithm first, fall back to PRS if that failed
1594 if (!(options & gcd_options::no_heur_gcd)) {
1595 bool found = heur_gcd(g, aex, bex, ca, cb, var);
1597 // heur_gcd have already computed cofactors...
1598 if (g.is_equal(_ex1)) {
1599 // ... but we want to keep them factored if possible.
1613 if (options & gcd_options::use_sr_gcd) {
1614 g = sr_gcd(aex, bex, var);
1617 for (std::size_t n = sym_stats.size(); n-- != 0; )
1618 vars.push_back(sym_stats[n].sym);
1619 g = chinrem_gcd(aex, bex, vars);
1622 if (g.is_equal(_ex1)) {
1623 // Keep cofactors factored if possible
1630 divide(aex, g, *ca, false);
1632 divide(bex, g, *cb, false);
1637 // gcd helper to handle partially factored polynomials (to avoid expanding
1638 // large expressions). Both arguments should be powers.
1639 static ex gcd_pf_pow_pow(const ex& a, const ex& b, ex* ca, ex* cb)
1642 const ex& exp_a = a.op(1);
1644 const ex& exp_b = b.op(1);
1646 // a = p^n, b = p^m, gcd = p^min(n, m)
1647 if (p.is_equal(pb)) {
1648 if (exp_a < exp_b) {
1652 *cb = pow(p, exp_b - exp_a);
1653 return pow(p, exp_a);
1656 *ca = pow(p, exp_a - exp_b);
1659 return pow(p, exp_b);
1664 ex p_gcd = gcd(p, pb, &p_co, &pb_co, false);
1665 // a(x) = p(x)^n, b(x) = p_b(x)^m, gcd (p, p_b) = 1 ==> gcd(a,b) = 1
1666 if (p_gcd.is_equal(_ex1)) {
1672 // XXX: do I need to check for p_gcd = -1?
1675 // there are common factors:
1676 // a(x) = g(x)^n A(x)^n, b(x) = g(x)^m B(x)^m ==>
1677 // gcd(a, b) = g(x)^n gcd(A(x)^n, g(x)^(n-m) B(x)^m
1678 if (exp_a < exp_b) {
1679 ex pg = gcd(pow(p_co, exp_a), pow(p_gcd, exp_b-exp_a)*pow(pb_co, exp_b), ca, cb, false);
1680 return pow(p_gcd, exp_a)*pg;
1682 ex pg = gcd(pow(p_gcd, exp_a - exp_b)*pow(p_co, exp_a), pow(pb_co, exp_b), ca, cb, false);
1683 return pow(p_gcd, exp_b)*pg;
1687 static ex gcd_pf_pow(const ex& a, const ex& b, ex* ca, ex* cb)
1689 if (is_exactly_a<power>(a) && is_exactly_a<power>(b))
1690 return gcd_pf_pow_pow(a, b, ca, cb);
1692 if (is_exactly_a<power>(b) && (! is_exactly_a<power>(a)))
1693 return gcd_pf_pow(b, a, cb, ca);
1695 GINAC_ASSERT(is_exactly_a<power>(a));
1698 const ex& exp_a = a.op(1);
1699 if (p.is_equal(b)) {
1700 // a = p^n, b = p, gcd = p
1702 *ca = pow(p, a.op(1) - 1);
1709 ex p_gcd = gcd(p, b, &p_co, &bpart_co, false);
1711 // a(x) = p(x)^n, gcd(p, b) = 1 ==> gcd(a, b) = 1
1712 if (p_gcd.is_equal(_ex1)) {
1719 // 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))
1720 ex rg = gcd(pow(p_gcd, exp_a-1)*pow(p_co, exp_a), bpart_co, ca, cb, false);
1724 static ex gcd_pf_mul(const ex& a, const ex& b, ex* ca, ex* cb)
1726 if (is_exactly_a<mul>(a) && is_exactly_a<mul>(b)
1727 && (b.nops() > a.nops()))
1728 return gcd_pf_mul(b, a, cb, ca);
1730 if (is_exactly_a<mul>(b) && (!is_exactly_a<mul>(a)))
1731 return gcd_pf_mul(b, a, cb, ca);
1733 GINAC_ASSERT(is_exactly_a<mul>(a));
1734 size_t num = a.nops();
1735 exvector g; g.reserve(num);
1736 exvector acc_ca; acc_ca.reserve(num);
1738 for (size_t i=0; i<num; i++) {
1739 ex part_ca, part_cb;
1740 g.push_back(gcd(a.op(i), part_b, &part_ca, &part_cb, false));
1741 acc_ca.push_back(part_ca);
1745 *ca = dynallocate<mul>(acc_ca);
1748 return dynallocate<mul>(g);
1751 /** Compute LCM (Least Common Multiple) of multivariate polynomials in Z[X].
1753 * @param a first multivariate polynomial
1754 * @param b second multivariate polynomial
1755 * @param check_args check whether a and b are polynomials with rational
1756 * coefficients (defaults to "true")
1757 * @return the LCM as a new expression */
1758 ex lcm(const ex &a, const ex &b, bool check_args)
1760 if (is_exactly_a<numeric>(a) && is_exactly_a<numeric>(b))
1761 return lcm(ex_to<numeric>(a), ex_to<numeric>(b));
1762 if (check_args && (!a.info(info_flags::rational_polynomial) || !b.info(info_flags::rational_polynomial)))
1763 throw(std::invalid_argument("lcm: arguments must be polynomials over the rationals"));
1766 ex g = gcd(a, b, &ca, &cb, false);
1772 * Square-free factorization
1775 /** Compute square-free factorization of multivariate polynomial a(x) using
1776 * Yun's algorithm. Used internally by sqrfree().
1778 * @param a multivariate polynomial over Z[X], treated here as univariate
1779 * polynomial in x (needs not be expanded).
1780 * @param x variable to factor in
1781 * @return vector of factors sorted in ascending degree */
1782 static exvector sqrfree_yun(const ex &a, const symbol &x)
1791 if (g.is_equal(_ex1)) {
1805 } while (!z.is_zero());
1810 /** Compute a square-free factorization of a multivariate polynomial in Q[X].
1812 * @param a multivariate polynomial over Q[X] (needs not be expanded)
1813 * @param l lst of variables to factor in, may be left empty for autodetection
1814 * @return a square-free factorization of \p a.
1817 * A polynomial \f$p(X) \in C[X]\f$ is said <EM>square-free</EM>
1818 * if, whenever any two polynomials \f$q(X)\f$ and \f$r(X)\f$
1821 * p(X) = q(X)^2 r(X),
1823 * we have \f$q(X) \in C\f$.
1824 * This means that \f$p(X)\f$ has no repeated factors, apart
1825 * eventually from constants.
1826 * Given a polynomial \f$p(X) \in C[X]\f$, we say that the
1829 * p(X) = b \cdot p_1(X)^{a_1} \cdot p_2(X)^{a_2} \cdots p_r(X)^{a_r}
1831 * is a <EM>square-free factorization</EM> of \f$p(X)\f$ if the
1832 * following conditions hold:
1833 * -# \f$b \in C\f$ and \f$b \neq 0\f$;
1834 * -# \f$a_i\f$ is a positive integer for \f$i = 1, \ldots, r\f$;
1835 * -# the degree of the polynomial \f$p_i\f$ is strictly positive
1836 * for \f$i = 1, \ldots, r\f$;
1837 * -# the polynomial \f$\Pi_{i=1}^r p_i(X)\f$ is square-free.
1839 * Square-free factorizations need not be unique. For example, if
1840 * \f$a_i\f$ is even, we could change the polynomial \f$p_i(X)\f$
1841 * into \f$-p_i(X)\f$.
1842 * Observe also that the factors \f$p_i(X)\f$ need not be irreducible
1845 ex sqrfree(const ex &a, const lst &l)
1847 if (is_exactly_a<numeric>(a) ||
1848 is_a<symbol>(a)) // shortcuts
1851 // If no lst of variables to factorize in was specified we have to
1852 // invent one now. Maybe one can optimize here by reversing the order
1853 // or so, I don't know.
1857 get_symbol_stats(a, _ex0, sdv);
1858 for (auto & it : sdv)
1859 args.append(it.sym);
1864 // Find the symbol to factor in at this stage
1865 if (!is_a<symbol>(args.op(0)))
1866 throw (std::runtime_error("sqrfree(): invalid factorization variable"));
1867 const symbol &x = ex_to<symbol>(args.op(0));
1869 // convert the argument from something in Q[X] to something in Z[X]
1870 const numeric lcm = lcm_of_coefficients_denominators(a);
1871 const ex tmp = multiply_lcm(a,lcm);
1874 exvector factors = sqrfree_yun(tmp, x);
1876 // construct the next list of symbols with the first element popped
1878 newargs.remove_first();
1880 // recurse down the factors in remaining variables
1881 if (newargs.nops()>0) {
1882 for (auto & it : factors)
1883 it = sqrfree(it, newargs);
1886 // Done with recursion, now construct the final result
1889 for (auto & it : factors)
1890 result *= pow(it, p++);
1892 // Yun's algorithm does not account for constant factors. (For univariate
1893 // polynomials it works only in the monic case.) We can correct this by
1894 // inserting what has been lost back into the result. For completeness
1895 // we'll also have to recurse down that factor in the remaining variables.
1896 if (newargs.nops()>0)
1897 result *= sqrfree(quo(tmp, result, x), newargs);
1899 result *= quo(tmp, result, x);
1901 // Put in the rational overall factor again and return
1902 return result * lcm.inverse();
1906 /** Compute square-free partial fraction decomposition of rational function
1909 * @param a rational function over Z[x], treated as univariate polynomial
1911 * @param x variable to factor in
1912 * @return decomposed rational function */
1913 ex sqrfree_parfrac(const ex & a, const symbol & x)
1915 // Find numerator and denominator
1916 ex nd = numer_denom(a);
1917 ex numer = nd.op(0), denom = nd.op(1);
1918 //clog << "numer = " << numer << ", denom = " << denom << endl;
1920 // Convert N(x)/D(x) -> Q(x) + R(x)/D(x), so degree(R) < degree(D)
1921 ex red_poly = quo(numer, denom, x), red_numer = rem(numer, denom, x).expand();
1922 //clog << "red_poly = " << red_poly << ", red_numer = " << red_numer << endl;
1924 // Factorize denominator and compute cofactors
1925 exvector yun = sqrfree_yun(denom, x);
1926 //clog << "yun factors: " << exprseq(yun) << endl;
1927 size_t num_yun = yun.size();
1928 exvector factor; factor.reserve(num_yun);
1929 exvector cofac; cofac.reserve(num_yun);
1930 for (size_t i=0; i<num_yun; i++) {
1931 if (!yun[i].is_equal(_ex1)) {
1932 for (size_t j=0; j<=i; j++) {
1933 factor.push_back(pow(yun[i], j+1));
1935 for (size_t k=0; k<num_yun; k++) {
1937 prod *= pow(yun[k], i-j);
1939 prod *= pow(yun[k], k+1);
1941 cofac.push_back(prod.expand());
1945 size_t num_factors = factor.size();
1946 //clog << "factors : " << exprseq(factor) << endl;
1947 //clog << "cofactors: " << exprseq(cofac) << endl;
1949 // Construct coefficient matrix for decomposition
1950 int max_denom_deg = denom.degree(x);
1951 matrix sys(max_denom_deg + 1, num_factors);
1952 matrix rhs(max_denom_deg + 1, 1);
1953 for (int i=0; i<=max_denom_deg; i++) {
1954 for (size_t j=0; j<num_factors; j++)
1955 sys(i, j) = cofac[j].coeff(x, i);
1956 rhs(i, 0) = red_numer.coeff(x, i);
1958 //clog << "coeffs: " << sys << endl;
1959 //clog << "rhs : " << rhs << endl;
1961 // Solve resulting linear system
1962 matrix vars(num_factors, 1);
1963 for (size_t i=0; i<num_factors; i++)
1964 vars(i, 0) = symbol();
1965 matrix sol = sys.solve(vars, rhs);
1967 // Sum up decomposed fractions
1969 for (size_t i=0; i<num_factors; i++)
1970 sum += sol(i, 0) / factor[i];
1972 return red_poly + sum;
1977 * Normal form of rational functions
1981 * Note: The internal normal() functions (= basic::normal() and overloaded
1982 * functions) all return lists of the form {numerator, denominator}. This
1983 * is to get around mul::eval()'s automatic expansion of numeric coefficients.
1984 * E.g. (a+b)/3 is automatically converted to a/3+b/3 but we want to keep
1985 * the information that (a+b) is the numerator and 3 is the denominator.
1989 /** Create a symbol for replacing the expression "e" (or return a previously
1990 * assigned symbol). The symbol and expression are appended to repl, for
1991 * a later application of subs().
1992 * @see ex::normal */
1993 static ex replace_with_symbol(const ex & e, exmap & repl, exmap & rev_lookup)
1995 // Since the repl contains replaced expressions we should search for them
1996 ex e_replaced = e.subs(repl, subs_options::no_pattern);
1998 // Expression already replaced? Then return the assigned symbol
1999 auto it = rev_lookup.find(e_replaced);
2000 if (it != rev_lookup.end())
2003 // Otherwise create new symbol and add to list, taking care that the
2004 // replacement expression doesn't itself contain symbols from repl,
2005 // because subs() is not recursive
2006 ex es = dynallocate<symbol>();
2007 repl.insert(std::make_pair(es, e_replaced));
2008 rev_lookup.insert(std::make_pair(e_replaced, es));
2012 /** Create a symbol for replacing the expression "e" (or return a previously
2013 * assigned symbol). The symbol and expression are appended to repl, and the
2014 * symbol is returned.
2015 * @see basic::to_rational
2016 * @see basic::to_polynomial */
2017 static ex replace_with_symbol(const ex & e, exmap & repl)
2019 // Since the repl contains replaced expressions we should search for them
2020 ex e_replaced = e.subs(repl, subs_options::no_pattern);
2022 // Expression already replaced? Then return the assigned symbol
2023 for (auto & it : repl)
2024 if (it.second.is_equal(e_replaced))
2027 // Otherwise create new symbol and add to list, taking care that the
2028 // replacement expression doesn't itself contain symbols from repl,
2029 // because subs() is not recursive
2030 ex es = dynallocate<symbol>();
2031 repl.insert(std::make_pair(es, e_replaced));
2036 /** Function object to be applied by basic::normal(). */
2037 struct normal_map_function : public map_function {
2038 ex operator()(const ex & e) override { return normal(e); }
2041 /** Default implementation of ex::normal(). It normalizes the children and
2042 * replaces the object with a temporary symbol.
2043 * @see ex::normal */
2044 ex basic::normal(exmap & repl, exmap & rev_lookup) const
2047 return dynallocate<lst>({replace_with_symbol(*this, repl, rev_lookup), _ex1});
2049 normal_map_function map_normal;
2050 return dynallocate<lst>({replace_with_symbol(map(map_normal), repl, rev_lookup), _ex1});
2054 /** Implementation of ex::normal() for symbols. This returns the unmodified symbol.
2055 * @see ex::normal */
2056 ex symbol::normal(exmap & repl, exmap & rev_lookup) const
2058 return dynallocate<lst>({*this, _ex1});
2062 /** Implementation of ex::normal() for a numeric. It splits complex numbers
2063 * into re+I*im and replaces I and non-rational real numbers with a temporary
2065 * @see ex::normal */
2066 ex numeric::normal(exmap & repl, exmap & rev_lookup) const
2068 numeric num = numer();
2071 if (num.is_real()) {
2072 if (!num.is_integer())
2073 numex = replace_with_symbol(numex, repl, rev_lookup);
2075 numeric re = num.real(), im = num.imag();
2076 ex re_ex = re.is_rational() ? re : replace_with_symbol(re, repl, rev_lookup);
2077 ex im_ex = im.is_rational() ? im : replace_with_symbol(im, repl, rev_lookup);
2078 numex = re_ex + im_ex * replace_with_symbol(I, repl, rev_lookup);
2081 // Denominator is always a real integer (see numeric::denom())
2082 return dynallocate<lst>({numex, denom()});
2086 /** Fraction cancellation.
2087 * @param n numerator
2088 * @param d denominator
2089 * @return cancelled fraction {n, d} as a list */
2090 static ex frac_cancel(const ex &n, const ex &d)
2094 numeric pre_factor = *_num1_p;
2096 //std::clog << "frac_cancel num = " << num << ", den = " << den << std::endl;
2098 // Handle trivial case where denominator is 1
2099 if (den.is_equal(_ex1))
2100 return dynallocate<lst>({num, den});
2102 // Handle special cases where numerator or denominator is 0
2104 return dynallocate<lst>({num, _ex1});
2105 if (den.expand().is_zero())
2106 throw(std::overflow_error("frac_cancel: division by zero in frac_cancel"));
2108 // Bring numerator and denominator to Z[X] by multiplying with
2109 // LCM of all coefficients' denominators
2110 numeric num_lcm = lcm_of_coefficients_denominators(num);
2111 numeric den_lcm = lcm_of_coefficients_denominators(den);
2112 num = multiply_lcm(num, num_lcm);
2113 den = multiply_lcm(den, den_lcm);
2114 pre_factor = den_lcm / num_lcm;
2116 // Cancel GCD from numerator and denominator
2118 if (gcd(num, den, &cnum, &cden, false) != _ex1) {
2123 // Make denominator unit normal (i.e. coefficient of first symbol
2124 // as defined by get_first_symbol() is made positive)
2125 if (is_exactly_a<numeric>(den)) {
2126 if (ex_to<numeric>(den).is_negative()) {
2132 if (get_first_symbol(den, x)) {
2133 GINAC_ASSERT(is_exactly_a<numeric>(den.unit(x)));
2134 if (ex_to<numeric>(den.unit(x)).is_negative()) {
2141 // Return result as list
2142 //std::clog << " returns num = " << num << ", den = " << den << ", pre_factor = " << pre_factor << std::endl;
2143 return dynallocate<lst>({num * pre_factor.numer(), den * pre_factor.denom()});
2147 /** Implementation of ex::normal() for a sum. It expands terms and performs
2148 * fractional addition.
2149 * @see ex::normal */
2150 ex add::normal(exmap & repl, exmap & rev_lookup) const
2152 // Normalize children and split each one into numerator and denominator
2153 exvector nums, dens;
2154 nums.reserve(seq.size()+1);
2155 dens.reserve(seq.size()+1);
2156 for (auto & it : seq) {
2157 ex n = ex_to<basic>(recombine_pair_to_ex(it)).normal(repl, rev_lookup);
2158 nums.push_back(n.op(0));
2159 dens.push_back(n.op(1));
2161 ex n = ex_to<numeric>(overall_coeff).normal(repl, rev_lookup);
2162 nums.push_back(n.op(0));
2163 dens.push_back(n.op(1));
2164 GINAC_ASSERT(nums.size() == dens.size());
2166 // Now, nums is a vector of all numerators and dens is a vector of
2168 //std::clog << "add::normal uses " << nums.size() << " summands:\n";
2170 // Add fractions sequentially
2171 auto num_it = nums.begin(), num_itend = nums.end();
2172 auto den_it = dens.begin(), den_itend = dens.end();
2173 //std::clog << " num = " << *num_it << ", den = " << *den_it << std::endl;
2174 ex num = *num_it++, den = *den_it++;
2175 while (num_it != num_itend) {
2176 //std::clog << " num = " << *num_it << ", den = " << *den_it << std::endl;
2177 ex next_num = *num_it++, next_den = *den_it++;
2179 // Trivially add sequences of fractions with identical denominators
2180 while ((den_it != den_itend) && next_den.is_equal(*den_it)) {
2181 next_num += *num_it;
2185 // Addition of two fractions, taking advantage of the fact that
2186 // the heuristic GCD algorithm computes the cofactors at no extra cost
2187 ex co_den1, co_den2;
2188 ex g = gcd(den, next_den, &co_den1, &co_den2, false);
2189 num = ((num * co_den2) + (next_num * co_den1)).expand();
2190 den *= co_den2; // this is the lcm(den, next_den)
2192 //std::clog << " common denominator = " << den << std::endl;
2194 // Cancel common factors from num/den
2195 return frac_cancel(num, den);
2199 /** Implementation of ex::normal() for a product. It cancels common factors
2201 * @see ex::normal() */
2202 ex mul::normal(exmap & repl, exmap & rev_lookup) const
2204 // Normalize children, separate into numerator and denominator
2205 exvector num; num.reserve(seq.size());
2206 exvector den; den.reserve(seq.size());
2208 for (auto & it : seq) {
2209 n = ex_to<basic>(recombine_pair_to_ex(it)).normal(repl, rev_lookup);
2210 num.push_back(n.op(0));
2211 den.push_back(n.op(1));
2213 n = ex_to<numeric>(overall_coeff).normal(repl, rev_lookup);
2214 num.push_back(n.op(0));
2215 den.push_back(n.op(1));
2217 // Perform fraction cancellation
2218 return frac_cancel(dynallocate<mul>(num), dynallocate<mul>(den));
2222 /** Implementation of ex::normal([B) for powers. It normalizes the basis,
2223 * distributes integer exponents to numerator and denominator, and replaces
2224 * non-integer powers by temporary symbols.
2225 * @see ex::normal */
2226 ex power::normal(exmap & repl, exmap & rev_lookup) const
2228 // Normalize basis and exponent (exponent gets reassembled)
2229 ex n_basis = ex_to<basic>(basis).normal(repl, rev_lookup);
2230 ex n_exponent = ex_to<basic>(exponent).normal(repl, rev_lookup);
2231 n_exponent = n_exponent.op(0) / n_exponent.op(1);
2233 if (n_exponent.info(info_flags::integer)) {
2235 if (n_exponent.info(info_flags::positive)) {
2237 // (a/b)^n -> {a^n, b^n}
2238 return dynallocate<lst>({pow(n_basis.op(0), n_exponent), pow(n_basis.op(1), n_exponent)});
2240 } else if (n_exponent.info(info_flags::negative)) {
2242 // (a/b)^-n -> {b^n, a^n}
2243 return dynallocate<lst>({pow(n_basis.op(1), -n_exponent), pow(n_basis.op(0), -n_exponent)});
2248 if (n_exponent.info(info_flags::positive)) {
2250 // (a/b)^x -> {sym((a/b)^x), 1}
2251 return dynallocate<lst>({replace_with_symbol(pow(n_basis.op(0) / n_basis.op(1), n_exponent), repl, rev_lookup), _ex1});
2253 } else if (n_exponent.info(info_flags::negative)) {
2255 if (n_basis.op(1).is_equal(_ex1)) {
2257 // a^-x -> {1, sym(a^x)}
2258 return dynallocate<lst>({_ex1, replace_with_symbol(pow(n_basis.op(0), -n_exponent), repl, rev_lookup)});
2262 // (a/b)^-x -> {sym((b/a)^x), 1}
2263 return dynallocate<lst>({replace_with_symbol(pow(n_basis.op(1) / n_basis.op(0), -n_exponent), repl, rev_lookup), _ex1});
2268 // (a/b)^x -> {sym((a/b)^x, 1}
2269 return dynallocate<lst>({replace_with_symbol(pow(n_basis.op(0) / n_basis.op(1), n_exponent), repl, rev_lookup), _ex1});
2273 /** Implementation of ex::normal() for pseries. It normalizes each coefficient
2274 * and replaces the series by a temporary symbol.
2275 * @see ex::normal */
2276 ex pseries::normal(exmap & repl, exmap & rev_lookup) const
2279 for (auto & it : seq) {
2280 ex restexp = it.rest.normal();
2281 if (!restexp.is_zero())
2282 newseq.push_back(expair(restexp, it.coeff));
2284 ex n = pseries(relational(var,point), std::move(newseq));
2285 return dynallocate<lst>({replace_with_symbol(n, repl, rev_lookup), _ex1});
2289 /** Normalization of rational functions.
2290 * This function converts an expression to its normal form
2291 * "numerator/denominator", where numerator and denominator are (relatively
2292 * prime) polynomials. Any subexpressions which are not rational functions
2293 * (like non-rational numbers, non-integer powers or functions like sin(),
2294 * cos() etc.) are replaced by temporary symbols which are re-substituted by
2295 * the (normalized) subexpressions before normal() returns (this way, any
2296 * expression can be treated as a rational function). normal() is applied
2297 * recursively to arguments of functions etc.
2299 * @return normalized expression */
2300 ex ex::normal() const
2302 exmap repl, rev_lookup;
2304 ex e = bp->normal(repl, rev_lookup);
2305 GINAC_ASSERT(is_a<lst>(e));
2307 // Re-insert replaced symbols
2309 e = e.subs(repl, subs_options::no_pattern);
2311 // Convert {numerator, denominator} form back to fraction
2312 return e.op(0) / e.op(1);
2315 /** Get numerator of an expression. If the expression is not of the normal
2316 * form "numerator/denominator", it is first converted to this form and
2317 * then the numerator is returned.
2320 * @return numerator */
2321 ex ex::numer() const
2323 exmap repl, rev_lookup;
2325 ex e = bp->normal(repl, rev_lookup);
2326 GINAC_ASSERT(is_a<lst>(e));
2328 // Re-insert replaced symbols
2332 return e.op(0).subs(repl, subs_options::no_pattern);
2335 /** Get denominator of an expression. If the expression is not of the normal
2336 * form "numerator/denominator", it is first converted to this form and
2337 * then the denominator is returned.
2340 * @return denominator */
2341 ex ex::denom() const
2343 exmap repl, rev_lookup;
2345 ex e = bp->normal(repl, rev_lookup);
2346 GINAC_ASSERT(is_a<lst>(e));
2348 // Re-insert replaced symbols
2352 return e.op(1).subs(repl, subs_options::no_pattern);
2355 /** Get numerator and denominator of an expression. If the expression is not
2356 * of the normal form "numerator/denominator", it is first converted to this
2357 * form and then a list [numerator, denominator] is returned.
2360 * @return a list [numerator, denominator] */
2361 ex ex::numer_denom() const
2363 exmap repl, rev_lookup;
2365 ex e = bp->normal(repl, rev_lookup);
2366 GINAC_ASSERT(is_a<lst>(e));
2368 // Re-insert replaced symbols
2372 return e.subs(repl, subs_options::no_pattern);
2376 /** Rationalization of non-rational functions.
2377 * This function converts a general expression to a rational function
2378 * by replacing all non-rational subexpressions (like non-rational numbers,
2379 * non-integer powers or functions like sin(), cos() etc.) to temporary
2380 * symbols. This makes it possible to use functions like gcd() and divide()
2381 * on non-rational functions by applying to_rational() on the arguments,
2382 * calling the desired function and re-substituting the temporary symbols
2383 * in the result. To make the last step possible, all temporary symbols and
2384 * their associated expressions are collected in the map specified by the
2385 * repl parameter, ready to be passed as an argument to ex::subs().
2387 * @param repl collects all temporary symbols and their replacements
2388 * @return rationalized expression */
2389 ex ex::to_rational(exmap & repl) const
2391 return bp->to_rational(repl);
2394 // GiNaC 1.1 compatibility function
2395 ex ex::to_rational(lst & repl_lst) const
2397 // Convert lst to exmap
2399 for (auto & it : repl_lst)
2400 m.insert(std::make_pair(it.op(0), it.op(1)));
2402 ex ret = bp->to_rational(m);
2404 // Convert exmap back to lst
2405 repl_lst.remove_all();
2407 repl_lst.append(it.first == it.second);
2412 ex ex::to_polynomial(exmap & repl) const
2414 return bp->to_polynomial(repl);
2417 // GiNaC 1.1 compatibility function
2418 ex ex::to_polynomial(lst & repl_lst) const
2420 // Convert lst to exmap
2422 for (auto & it : repl_lst)
2423 m.insert(std::make_pair(it.op(0), it.op(1)));
2425 ex ret = bp->to_polynomial(m);
2427 // Convert exmap back to lst
2428 repl_lst.remove_all();
2430 repl_lst.append(it.first == it.second);
2435 /** Default implementation of ex::to_rational(). This replaces the object with
2436 * a temporary symbol. */
2437 ex basic::to_rational(exmap & repl) const
2439 return replace_with_symbol(*this, repl);
2442 ex basic::to_polynomial(exmap & repl) const
2444 return replace_with_symbol(*this, repl);
2448 /** Implementation of ex::to_rational() for symbols. This returns the
2449 * unmodified symbol. */
2450 ex symbol::to_rational(exmap & repl) const
2455 /** Implementation of ex::to_polynomial() for symbols. This returns the
2456 * unmodified symbol. */
2457 ex symbol::to_polynomial(exmap & repl) const
2463 /** Implementation of ex::to_rational() for a numeric. It splits complex
2464 * numbers into re+I*im and replaces I and non-rational real numbers with a
2465 * temporary symbol. */
2466 ex numeric::to_rational(exmap & repl) const
2470 return replace_with_symbol(*this, repl);
2472 numeric re = real();
2473 numeric im = imag();
2474 ex re_ex = re.is_rational() ? re : replace_with_symbol(re, repl);
2475 ex im_ex = im.is_rational() ? im : replace_with_symbol(im, repl);
2476 return re_ex + im_ex * replace_with_symbol(I, repl);
2481 /** Implementation of ex::to_polynomial() for a numeric. It splits complex
2482 * numbers into re+I*im and replaces I and non-integer real numbers with a
2483 * temporary symbol. */
2484 ex numeric::to_polynomial(exmap & repl) const
2488 return replace_with_symbol(*this, repl);
2490 numeric re = real();
2491 numeric im = imag();
2492 ex re_ex = re.is_integer() ? re : replace_with_symbol(re, repl);
2493 ex im_ex = im.is_integer() ? im : replace_with_symbol(im, repl);
2494 return re_ex + im_ex * replace_with_symbol(I, repl);
2500 /** Implementation of ex::to_rational() for powers. It replaces non-integer
2501 * powers by temporary symbols. */
2502 ex power::to_rational(exmap & repl) const
2504 if (exponent.info(info_flags::integer))
2505 return pow(basis.to_rational(repl), exponent);
2507 return replace_with_symbol(*this, repl);
2510 /** Implementation of ex::to_polynomial() for powers. It replaces non-posint
2511 * powers by temporary symbols. */
2512 ex power::to_polynomial(exmap & repl) const
2514 if (exponent.info(info_flags::posint))
2515 return pow(basis.to_rational(repl), exponent);
2516 else if (exponent.info(info_flags::negint))
2518 ex basis_pref = collect_common_factors(basis);
2519 if (is_exactly_a<mul>(basis_pref) || is_exactly_a<power>(basis_pref)) {
2520 // (A*B)^n will be automagically transformed to A^n*B^n
2521 ex t = pow(basis_pref, exponent);
2522 return t.to_polynomial(repl);
2525 return pow(replace_with_symbol(pow(basis, _ex_1), repl), -exponent);
2528 return replace_with_symbol(*this, repl);
2532 /** Implementation of ex::to_rational() for expairseqs. */
2533 ex expairseq::to_rational(exmap & repl) const
2536 s.reserve(seq.size());
2537 for (auto & it : seq)
2538 s.push_back(split_ex_to_pair(recombine_pair_to_ex(it).to_rational(repl)));
2540 ex oc = overall_coeff.to_rational(repl);
2541 if (oc.info(info_flags::numeric))
2542 return thisexpairseq(std::move(s), overall_coeff);
2544 s.push_back(expair(oc, _ex1));
2545 return thisexpairseq(std::move(s), default_overall_coeff());
2548 /** Implementation of ex::to_polynomial() for expairseqs. */
2549 ex expairseq::to_polynomial(exmap & repl) const
2552 s.reserve(seq.size());
2553 for (auto & it : seq)
2554 s.push_back(split_ex_to_pair(recombine_pair_to_ex(it).to_polynomial(repl)));
2556 ex oc = overall_coeff.to_polynomial(repl);
2557 if (oc.info(info_flags::numeric))
2558 return thisexpairseq(std::move(s), overall_coeff);
2560 s.push_back(expair(oc, _ex1));
2561 return thisexpairseq(std::move(s), default_overall_coeff());
2565 /** Remove the common factor in the terms of a sum 'e' by calculating the GCD,
2566 * and multiply it into the expression 'factor' (which needs to be initialized
2567 * to 1, unless you're accumulating factors). */
2568 static ex find_common_factor(const ex & e, ex & factor, exmap & repl)
2570 if (is_exactly_a<add>(e)) {
2572 size_t num = e.nops();
2573 exvector terms; terms.reserve(num);
2576 // Find the common GCD
2577 for (size_t i=0; i<num; i++) {
2578 ex x = e.op(i).to_polynomial(repl);
2580 if (is_exactly_a<add>(x) || is_exactly_a<mul>(x) || is_a<power>(x)) {
2582 x = find_common_factor(x, f, repl);
2594 if (gc.is_equal(_ex1))
2597 // The GCD is the factor we pull out
2600 // Now divide all terms by the GCD
2601 for (size_t i=0; i<num; i++) {
2604 // Try to avoid divide() because it expands the polynomial
2606 if (is_exactly_a<mul>(t)) {
2607 for (size_t j=0; j<t.nops(); j++) {
2608 if (t.op(j).is_equal(gc)) {
2609 exvector v; v.reserve(t.nops());
2610 for (size_t k=0; k<t.nops(); k++) {
2614 v.push_back(t.op(k));
2616 t = dynallocate<mul>(v);
2626 return dynallocate<add>(terms);
2628 } else if (is_exactly_a<mul>(e)) {
2630 size_t num = e.nops();
2631 exvector v; v.reserve(num);
2633 for (size_t i=0; i<num; i++)
2634 v.push_back(find_common_factor(e.op(i), factor, repl));
2636 return dynallocate<mul>(v);
2638 } else if (is_exactly_a<power>(e)) {
2639 const ex e_exp(e.op(1));
2640 if (e_exp.info(info_flags::integer)) {
2641 ex eb = e.op(0).to_polynomial(repl);
2642 ex factor_local(_ex1);
2643 ex pre_res = find_common_factor(eb, factor_local, repl);
2644 factor *= pow(factor_local, e_exp);
2645 return pow(pre_res, e_exp);
2648 return e.to_polynomial(repl);
2655 /** Collect common factors in sums. This converts expressions like
2656 * 'a*(b*x+b*y)' to 'a*b*(x+y)'. */
2657 ex collect_common_factors(const ex & e)
2659 if (is_exactly_a<add>(e) || is_exactly_a<mul>(e) || is_exactly_a<power>(e)) {
2663 ex r = find_common_factor(e, factor, repl);
2664 return factor.subs(repl, subs_options::no_pattern) * r.subs(repl, subs_options::no_pattern);
2671 /** Resultant of two expressions e1,e2 with respect to symbol s.
2672 * Method: Compute determinant of Sylvester matrix of e1,e2,s. */
2673 ex resultant(const ex & e1, const ex & e2, const ex & s)
2675 const ex ee1 = e1.expand();
2676 const ex ee2 = e2.expand();
2677 if (!ee1.info(info_flags::polynomial) ||
2678 !ee2.info(info_flags::polynomial))
2679 throw(std::runtime_error("resultant(): arguments must be polynomials"));
2681 const int h1 = ee1.degree(s);
2682 const int l1 = ee1.ldegree(s);
2683 const int h2 = ee2.degree(s);
2684 const int l2 = ee2.ldegree(s);
2686 const int msize = h1 + h2;
2687 matrix m(msize, msize);
2689 for (int l = h1; l >= l1; --l) {
2690 const ex e = ee1.coeff(s, l);
2691 for (int k = 0; k < h2; ++k)
2694 for (int l = h2; l >= l2; --l) {
2695 const ex e = ee2.coeff(s, l);
2696 for (int k = 0; k < h1; ++k)
2697 m(k+h2, k+h2-l) = e;
2700 return m.determinant();
2704 } // namespace GiNaC