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 /** Reference to symbol */
126 /** Highest degree of symbol in polynomial "a" */
129 /** Highest degree of symbol in polynomial "b" */
132 /** Lowest degree of symbol in polynomial "a" */
135 /** Lowest degree of symbol in polynomial "b" */
138 /** Maximum of deg_a and deg_b (Used for sorting) */
141 /** Maximum number of terms of leading coefficient of symbol in both polynomials */
144 /** Commparison operator for sorting */
145 bool operator<(const sym_desc &x) const
147 if (max_deg == x.max_deg)
148 return max_lcnops < x.max_lcnops;
150 return max_deg < x.max_deg;
154 // Vector of sym_desc structures
155 typedef std::vector<sym_desc> sym_desc_vec;
157 // Add symbol the sym_desc_vec (used internally by get_symbol_stats())
158 static void add_symbol(const ex &s, sym_desc_vec &v)
160 sym_desc_vec::const_iterator it = v.begin(), itend = v.end();
161 while (it != itend) {
162 if (it->sym.is_equal(s)) // If it's already in there, don't add it a second time
171 // Collect all symbols of an expression (used internally by get_symbol_stats())
172 static void collect_symbols(const ex &e, sym_desc_vec &v)
174 if (is_a<symbol>(e)) {
176 } else if (is_exactly_a<add>(e) || is_exactly_a<mul>(e)) {
177 for (size_t i=0; i<e.nops(); i++)
178 collect_symbols(e.op(i), v);
179 } else if (is_exactly_a<power>(e)) {
180 collect_symbols(e.op(0), v);
184 /** Collect statistical information about symbols in polynomials.
185 * This function fills in a vector of "sym_desc" structs which contain
186 * information about the highest and lowest degrees of all symbols that
187 * appear in two polynomials. The vector is then sorted by minimum
188 * degree (lowest to highest). The information gathered by this
189 * function is used by the GCD routines to identify trivial factors
190 * and to determine which variable to choose as the main variable
191 * for GCD computation.
193 * @param a first multivariate polynomial
194 * @param b second multivariate polynomial
195 * @param v vector of sym_desc structs (filled in) */
196 static void get_symbol_stats(const ex &a, const ex &b, sym_desc_vec &v)
198 collect_symbols(a.eval(), v); // eval() to expand assigned symbols
199 collect_symbols(b.eval(), v);
200 sym_desc_vec::iterator it = v.begin(), itend = v.end();
201 while (it != itend) {
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);
212 std::sort(v.begin(), v.end());
215 std::clog << "Symbols:\n";
216 it = v.begin(); itend = v.end();
217 while (it != itend) {
218 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;
219 std::clog << " lcoeff_a=" << a.lcoeff(it->sym) << ", lcoeff_b=" << b.lcoeff(it->sym) << endl;
227 * Computation of LCM of denominators of coefficients of a polynomial
230 // Compute LCM of denominators of coefficients by going through the
231 // expression recursively (used internally by lcm_of_coefficients_denominators())
232 static numeric lcmcoeff(const ex &e, const numeric &l)
234 if (e.info(info_flags::rational))
235 return lcm(ex_to<numeric>(e).denom(), l);
236 else if (is_exactly_a<add>(e)) {
237 numeric c = *_num1_p;
238 for (size_t i=0; i<e.nops(); i++)
239 c = lcmcoeff(e.op(i), c);
241 } else if (is_exactly_a<mul>(e)) {
242 numeric c = *_num1_p;
243 for (size_t i=0; i<e.nops(); i++)
244 c *= lcmcoeff(e.op(i), *_num1_p);
246 } else if (is_exactly_a<power>(e)) {
247 if (is_a<symbol>(e.op(0)))
250 return pow(lcmcoeff(e.op(0), l), ex_to<numeric>(e.op(1)));
255 /** Compute LCM of denominators of coefficients of a polynomial.
256 * Given a polynomial with rational coefficients, this function computes
257 * the LCM of the denominators of all coefficients. This can be used
258 * to bring a polynomial from Q[X] to Z[X].
260 * @param e multivariate polynomial (need not be expanded)
261 * @return LCM of denominators of coefficients */
262 static numeric lcm_of_coefficients_denominators(const ex &e)
264 return lcmcoeff(e, *_num1_p);
267 /** Bring polynomial from Q[X] to Z[X] by multiplying in the previously
268 * determined LCM of the coefficient's denominators.
270 * @param e multivariate polynomial (need not be expanded)
271 * @param lcm LCM to multiply in */
272 static ex multiply_lcm(const ex &e, const numeric &lcm)
274 if (is_exactly_a<mul>(e)) {
275 size_t num = e.nops();
276 exvector v; v.reserve(num + 1);
277 numeric lcm_accum = *_num1_p;
278 for (size_t i=0; i<num; i++) {
279 numeric op_lcm = lcmcoeff(e.op(i), *_num1_p);
280 v.push_back(multiply_lcm(e.op(i), op_lcm));
283 v.push_back(lcm / lcm_accum);
284 return (new mul(v))->setflag(status_flags::dynallocated);
285 } else if (is_exactly_a<add>(e)) {
286 size_t num = e.nops();
287 exvector v; v.reserve(num);
288 for (size_t i=0; i<num; i++)
289 v.push_back(multiply_lcm(e.op(i), lcm));
290 return (new add(v))->setflag(status_flags::dynallocated);
291 } else if (is_exactly_a<power>(e)) {
292 if (is_a<symbol>(e.op(0)))
295 numeric root_of_lcm = lcm.power(ex_to<numeric>(e.op(1)).inverse());
296 if (root_of_lcm.is_rational())
297 return pow(multiply_lcm(e.op(0), root_of_lcm), e.op(1));
306 /** Compute the integer content (= GCD of all numeric coefficients) of an
307 * expanded polynomial. For a polynomial with rational coefficients, this
308 * returns g/l where g is the GCD of the coefficients' numerators and l
309 * is the LCM of the coefficients' denominators.
311 * @return integer content */
312 numeric ex::integer_content() const
314 return bp->integer_content();
317 numeric basic::integer_content() const
322 numeric numeric::integer_content() const
327 numeric add::integer_content() const
329 epvector::const_iterator it = seq.begin();
330 epvector::const_iterator itend = seq.end();
331 numeric c = *_num0_p, l = *_num1_p;
332 while (it != itend) {
333 GINAC_ASSERT(!is_exactly_a<numeric>(it->rest));
334 GINAC_ASSERT(is_exactly_a<numeric>(it->coeff));
335 c = gcd(ex_to<numeric>(it->coeff).numer(), c);
336 l = lcm(ex_to<numeric>(it->coeff).denom(), l);
339 GINAC_ASSERT(is_exactly_a<numeric>(overall_coeff));
340 c = gcd(ex_to<numeric>(overall_coeff).numer(), c);
341 l = lcm(ex_to<numeric>(overall_coeff).denom(), l);
345 numeric mul::integer_content() const
347 #ifdef DO_GINAC_ASSERT
348 epvector::const_iterator it = seq.begin();
349 epvector::const_iterator itend = seq.end();
350 while (it != itend) {
351 GINAC_ASSERT(!is_exactly_a<numeric>(recombine_pair_to_ex(*it)));
354 #endif // def DO_GINAC_ASSERT
355 GINAC_ASSERT(is_exactly_a<numeric>(overall_coeff));
356 return abs(ex_to<numeric>(overall_coeff));
361 * Polynomial quotients and remainders
364 /** Quotient q(x) of polynomials a(x) and b(x) in Q[x].
365 * It satisfies a(x)=b(x)*q(x)+r(x).
367 * @param a first polynomial in x (dividend)
368 * @param b second polynomial in x (divisor)
369 * @param x a and b are polynomials in x
370 * @param check_args check whether a and b are polynomials with rational
371 * coefficients (defaults to "true")
372 * @return quotient of a and b in Q[x] */
373 ex quo(const ex &a, const ex &b, const ex &x, bool check_args)
376 throw(std::overflow_error("quo: division by zero"));
377 if (is_exactly_a<numeric>(a) && is_exactly_a<numeric>(b))
383 if (check_args && (!a.info(info_flags::rational_polynomial) || !b.info(info_flags::rational_polynomial)))
384 throw(std::invalid_argument("quo: arguments must be polynomials over the rationals"));
386 // Polynomial long division
390 int bdeg = b.degree(x);
391 int rdeg = r.degree(x);
392 ex blcoeff = b.expand().coeff(x, bdeg);
393 bool blcoeff_is_numeric = is_exactly_a<numeric>(blcoeff);
394 exvector v; v.reserve(std::max(rdeg - bdeg + 1, 0));
395 while (rdeg >= bdeg) {
396 ex term, rcoeff = r.coeff(x, rdeg);
397 if (blcoeff_is_numeric)
398 term = rcoeff / blcoeff;
400 if (!divide(rcoeff, blcoeff, term, false))
401 return (new fail())->setflag(status_flags::dynallocated);
403 term *= power(x, rdeg - bdeg);
405 r -= (term * b).expand();
410 return (new add(v))->setflag(status_flags::dynallocated);
414 /** Remainder r(x) of polynomials a(x) and b(x) in Q[x].
415 * It satisfies a(x)=b(x)*q(x)+r(x).
417 * @param a first polynomial in x (dividend)
418 * @param b second polynomial in x (divisor)
419 * @param x a and b are polynomials in x
420 * @param check_args check whether a and b are polynomials with rational
421 * coefficients (defaults to "true")
422 * @return remainder of a(x) and b(x) in Q[x] */
423 ex rem(const ex &a, const ex &b, const ex &x, bool check_args)
426 throw(std::overflow_error("rem: division by zero"));
427 if (is_exactly_a<numeric>(a)) {
428 if (is_exactly_a<numeric>(b))
437 if (check_args && (!a.info(info_flags::rational_polynomial) || !b.info(info_flags::rational_polynomial)))
438 throw(std::invalid_argument("rem: arguments must be polynomials over the rationals"));
440 // Polynomial long division
444 int bdeg = b.degree(x);
445 int rdeg = r.degree(x);
446 ex blcoeff = b.expand().coeff(x, bdeg);
447 bool blcoeff_is_numeric = is_exactly_a<numeric>(blcoeff);
448 while (rdeg >= bdeg) {
449 ex term, rcoeff = r.coeff(x, rdeg);
450 if (blcoeff_is_numeric)
451 term = rcoeff / blcoeff;
453 if (!divide(rcoeff, blcoeff, term, false))
454 return (new fail())->setflag(status_flags::dynallocated);
456 term *= power(x, rdeg - bdeg);
457 r -= (term * b).expand();
466 /** Decompose rational function a(x)=N(x)/D(x) into P(x)+n(x)/D(x)
467 * with degree(n, x) < degree(D, x).
469 * @param a rational function in x
470 * @param x a is a function of x
471 * @return decomposed function. */
472 ex decomp_rational(const ex &a, const ex &x)
474 ex nd = numer_denom(a);
475 ex numer = nd.op(0), denom = nd.op(1);
476 ex q = quo(numer, denom, x);
477 if (is_exactly_a<fail>(q))
480 return q + rem(numer, denom, x) / denom;
484 /** Pseudo-remainder of polynomials a(x) and b(x) in Q[x].
486 * @param a first polynomial in x (dividend)
487 * @param b second polynomial in x (divisor)
488 * @param x a and b are polynomials in x
489 * @param check_args check whether a and b are polynomials with rational
490 * coefficients (defaults to "true")
491 * @return pseudo-remainder of a(x) and b(x) in Q[x] */
492 ex prem(const ex &a, const ex &b, const ex &x, bool check_args)
495 throw(std::overflow_error("prem: division by zero"));
496 if (is_exactly_a<numeric>(a)) {
497 if (is_exactly_a<numeric>(b))
502 if (check_args && (!a.info(info_flags::rational_polynomial) || !b.info(info_flags::rational_polynomial)))
503 throw(std::invalid_argument("prem: arguments must be polynomials over the rationals"));
505 // Polynomial long division
508 int rdeg = r.degree(x);
509 int bdeg = eb.degree(x);
512 blcoeff = eb.coeff(x, bdeg);
516 eb -= blcoeff * power(x, bdeg);
520 int delta = rdeg - bdeg + 1, i = 0;
521 while (rdeg >= bdeg && !r.is_zero()) {
522 ex rlcoeff = r.coeff(x, rdeg);
523 ex term = (power(x, rdeg - bdeg) * eb * rlcoeff).expand();
527 r -= rlcoeff * power(x, rdeg);
528 r = (blcoeff * r).expand() - term;
532 return power(blcoeff, delta - i) * r;
536 /** Sparse pseudo-remainder of polynomials a(x) and b(x) in Q[x].
538 * @param a first polynomial in x (dividend)
539 * @param b second polynomial in x (divisor)
540 * @param x a and b are polynomials in x
541 * @param check_args check whether a and b are polynomials with rational
542 * coefficients (defaults to "true")
543 * @return sparse pseudo-remainder of a(x) and b(x) in Q[x] */
544 ex sprem(const ex &a, const ex &b, const ex &x, bool check_args)
547 throw(std::overflow_error("prem: division by zero"));
548 if (is_exactly_a<numeric>(a)) {
549 if (is_exactly_a<numeric>(b))
554 if (check_args && (!a.info(info_flags::rational_polynomial) || !b.info(info_flags::rational_polynomial)))
555 throw(std::invalid_argument("prem: arguments must be polynomials over the rationals"));
557 // Polynomial long division
560 int rdeg = r.degree(x);
561 int bdeg = eb.degree(x);
564 blcoeff = eb.coeff(x, bdeg);
568 eb -= blcoeff * power(x, bdeg);
572 while (rdeg >= bdeg && !r.is_zero()) {
573 ex rlcoeff = r.coeff(x, rdeg);
574 ex term = (power(x, rdeg - bdeg) * eb * rlcoeff).expand();
578 r -= rlcoeff * power(x, rdeg);
579 r = (blcoeff * r).expand() - term;
586 /** Exact polynomial division of a(X) by b(X) in Q[X].
588 * @param a first multivariate polynomial (dividend)
589 * @param b second multivariate polynomial (divisor)
590 * @param q quotient (returned)
591 * @param check_args check whether a and b are polynomials with rational
592 * coefficients (defaults to "true")
593 * @return "true" when exact division succeeds (quotient returned in q),
594 * "false" otherwise (q left untouched) */
595 bool divide(const ex &a, const ex &b, ex &q, bool check_args)
598 throw(std::overflow_error("divide: division by zero"));
603 if (is_exactly_a<numeric>(b)) {
606 } else if (is_exactly_a<numeric>(a))
614 if (check_args && (!a.info(info_flags::rational_polynomial) ||
615 !b.info(info_flags::rational_polynomial)))
616 throw(std::invalid_argument("divide: arguments must be polynomials over the rationals"));
620 if (!get_first_symbol(a, x) && !get_first_symbol(b, x))
621 throw(std::invalid_argument("invalid expression in divide()"));
623 // Try to avoid expanding partially factored expressions.
624 if (is_exactly_a<mul>(b)) {
625 // Divide sequentially by each term
626 ex rem_new, rem_old = a;
627 for (size_t i=0; i < b.nops(); i++) {
628 if (! divide(rem_old, b.op(i), rem_new, false))
634 } else if (is_exactly_a<power>(b)) {
635 const ex& bb(b.op(0));
636 int exp_b = ex_to<numeric>(b.op(1)).to_int();
637 ex rem_new, rem_old = a;
638 for (int i=exp_b; i>0; i--) {
639 if (! divide(rem_old, bb, rem_new, false))
647 if (is_exactly_a<mul>(a)) {
648 // Divide sequentially each term. If some term in a is divisible
649 // by b we are done... and if not, we can't really say anything.
652 bool divisible_p = false;
653 for (i=0; i < a.nops(); ++i) {
654 if (divide(a.op(i), b, rem_i, false)) {
661 resv.reserve(a.nops());
662 for (size_t j=0; j < a.nops(); j++) {
664 resv.push_back(rem_i);
666 resv.push_back(a.op(j));
668 q = (new mul(resv))->setflag(status_flags::dynallocated);
671 } else if (is_exactly_a<power>(a)) {
672 // The base itself might be divisible by b, in that case we don't
674 const ex& ab(a.op(0));
675 int a_exp = ex_to<numeric>(a.op(1)).to_int();
677 if (divide(ab, b, rem_i, false)) {
678 q = rem_i*power(ab, a_exp - 1);
681 // code below is commented-out because it leads to a significant slowdown
682 // for (int i=2; i < a_exp; i++) {
683 // if (divide(power(ab, i), b, rem_i, false)) {
684 // q = rem_i*power(ab, a_exp - i);
687 // } // ... so we *really* need to expand expression.
690 // Polynomial long division (recursive)
696 int bdeg = b.degree(x);
697 int rdeg = r.degree(x);
698 ex blcoeff = b.expand().coeff(x, bdeg);
699 bool blcoeff_is_numeric = is_exactly_a<numeric>(blcoeff);
700 exvector v; v.reserve(std::max(rdeg - bdeg + 1, 0));
701 while (rdeg >= bdeg) {
702 ex term, rcoeff = r.coeff(x, rdeg);
703 if (blcoeff_is_numeric)
704 term = rcoeff / blcoeff;
706 if (!divide(rcoeff, blcoeff, term, false))
708 term *= power(x, rdeg - bdeg);
710 r -= (term * b).expand();
712 q = (new add(v))->setflag(status_flags::dynallocated);
726 typedef std::pair<ex, ex> ex2;
727 typedef std::pair<ex, bool> exbool;
730 bool operator() (const ex2 &p, const ex2 &q) const
732 int cmp = p.first.compare(q.first);
733 return ((cmp<0) || (!(cmp>0) && p.second.compare(q.second)<0));
737 typedef std::map<ex2, exbool, ex2_less> ex2_exbool_remember;
741 /** Exact polynomial division of a(X) by b(X) in Z[X].
742 * This functions works like divide() but the input and output polynomials are
743 * in Z[X] instead of Q[X] (i.e. they have integer coefficients). Unlike
744 * divide(), it doesn't check whether the input polynomials really are integer
745 * polynomials, so be careful of what you pass in. Also, you have to run
746 * get_symbol_stats() over the input polynomials before calling this function
747 * and pass an iterator to the first element of the sym_desc vector. This
748 * function is used internally by the heur_gcd().
750 * @param a first multivariate polynomial (dividend)
751 * @param b second multivariate polynomial (divisor)
752 * @param q quotient (returned)
753 * @param var iterator to first element of vector of sym_desc structs
754 * @return "true" when exact division succeeds (the quotient is returned in
755 * q), "false" otherwise.
756 * @see get_symbol_stats, heur_gcd */
757 static bool divide_in_z(const ex &a, const ex &b, ex &q, sym_desc_vec::const_iterator var)
761 throw(std::overflow_error("divide_in_z: division by zero"));
762 if (b.is_equal(_ex1)) {
766 if (is_exactly_a<numeric>(a)) {
767 if (is_exactly_a<numeric>(b)) {
769 return q.info(info_flags::integer);
782 static ex2_exbool_remember dr_remember;
783 ex2_exbool_remember::const_iterator remembered = dr_remember.find(ex2(a, b));
784 if (remembered != dr_remember.end()) {
785 q = remembered->second.first;
786 return remembered->second.second;
790 if (is_exactly_a<power>(b)) {
791 const ex& bb(b.op(0));
793 int exp_b = ex_to<numeric>(b.op(1)).to_int();
794 for (int i=exp_b; i>0; i--) {
795 if (!divide_in_z(qbar, bb, q, var))
802 if (is_exactly_a<mul>(b)) {
804 for (const_iterator itrb = b.begin(); itrb != b.end(); ++itrb) {
805 sym_desc_vec sym_stats;
806 get_symbol_stats(a, *itrb, sym_stats);
807 if (!divide_in_z(qbar, *itrb, q, sym_stats.begin()))
816 const ex &x = var->sym;
819 int adeg = a.degree(x), bdeg = b.degree(x);
823 #if USE_TRIAL_DIVISION
825 // Trial division with polynomial interpolation
828 // Compute values at evaluation points 0..adeg
829 vector<numeric> alpha; alpha.reserve(adeg + 1);
830 exvector u; u.reserve(adeg + 1);
831 numeric point = *_num0_p;
833 for (i=0; i<=adeg; i++) {
834 ex bs = b.subs(x == point, subs_options::no_pattern);
835 while (bs.is_zero()) {
837 bs = b.subs(x == point, subs_options::no_pattern);
839 if (!divide_in_z(a.subs(x == point, subs_options::no_pattern), bs, c, var+1))
841 alpha.push_back(point);
847 vector<numeric> rcp; rcp.reserve(adeg + 1);
848 rcp.push_back(*_num0_p);
849 for (k=1; k<=adeg; k++) {
850 numeric product = alpha[k] - alpha[0];
852 product *= alpha[k] - alpha[i];
853 rcp.push_back(product.inverse());
856 // Compute Newton coefficients
857 exvector v; v.reserve(adeg + 1);
859 for (k=1; k<=adeg; k++) {
861 for (i=k-2; i>=0; i--)
862 temp = temp * (alpha[k] - alpha[i]) + v[i];
863 v.push_back((u[k] - temp) * rcp[k]);
866 // Convert from Newton form to standard form
868 for (k=adeg-1; k>=0; k--)
869 c = c * (x - alpha[k]) + v[k];
871 if (c.degree(x) == (adeg - bdeg)) {
879 // Polynomial long division (recursive)
885 ex blcoeff = eb.coeff(x, bdeg);
886 exvector v; v.reserve(std::max(rdeg - bdeg + 1, 0));
887 while (rdeg >= bdeg) {
888 ex term, rcoeff = r.coeff(x, rdeg);
889 if (!divide_in_z(rcoeff, blcoeff, term, var+1))
891 term = (term * power(x, rdeg - bdeg)).expand();
893 r -= (term * eb).expand();
895 q = (new add(v))->setflag(status_flags::dynallocated);
897 dr_remember[ex2(a, b)] = exbool(q, true);
904 dr_remember[ex2(a, b)] = exbool(q, false);
913 * Separation of unit part, content part and primitive part of polynomials
916 /** Compute unit part (= sign of leading coefficient) of a multivariate
917 * polynomial in Q[x]. The product of unit part, content part, and primitive
918 * part is the polynomial itself.
920 * @param x main variable
922 * @see ex::content, ex::primpart, ex::unitcontprim */
923 ex ex::unit(const ex &x) const
925 ex c = expand().lcoeff(x);
926 if (is_exactly_a<numeric>(c))
927 return c.info(info_flags::negative) ?_ex_1 : _ex1;
930 if (get_first_symbol(c, y))
933 throw(std::invalid_argument("invalid expression in unit()"));
938 /** Compute content part (= unit normal GCD of all coefficients) of a
939 * multivariate polynomial in Q[x]. The product of unit part, content part,
940 * and primitive part is the polynomial itself.
942 * @param x main variable
943 * @return content part
944 * @see ex::unit, ex::primpart, ex::unitcontprim */
945 ex ex::content(const ex &x) const
947 if (is_exactly_a<numeric>(*this))
948 return info(info_flags::negative) ? -*this : *this;
954 // First, divide out the integer content (which we can calculate very efficiently).
955 // If the leading coefficient of the quotient is an integer, we are done.
956 ex c = e.integer_content();
958 int deg = r.degree(x);
959 ex lcoeff = r.coeff(x, deg);
960 if (lcoeff.info(info_flags::integer))
963 // GCD of all coefficients
964 int ldeg = r.ldegree(x);
966 return lcoeff * c / lcoeff.unit(x);
968 for (int i=ldeg; i<=deg; i++)
969 cont = gcd(r.coeff(x, i), cont, NULL, NULL, false);
974 /** Compute primitive part of a multivariate polynomial in Q[x]. The result
975 * will be a unit-normal polynomial with a content part of 1. The product
976 * of unit part, content part, and primitive part is the polynomial itself.
978 * @param x main variable
979 * @return primitive part
980 * @see ex::unit, ex::content, ex::unitcontprim */
981 ex ex::primpart(const ex &x) const
983 // We need to compute the unit and content anyway, so call unitcontprim()
985 unitcontprim(x, u, c, p);
990 /** Compute primitive part of a multivariate polynomial in Q[x] when the
991 * content part is already known. This function is faster in computing the
992 * primitive part than the previous function.
994 * @param x main variable
995 * @param c previously computed content part
996 * @return primitive part */
997 ex ex::primpart(const ex &x, const ex &c) const
999 if (is_zero() || c.is_zero())
1001 if (is_exactly_a<numeric>(*this))
1004 // Divide by unit and content to get primitive part
1006 if (is_exactly_a<numeric>(c))
1007 return *this / (c * u);
1009 return quo(*this, c * u, x, false);
1013 /** Compute unit part, content part, and primitive part of a multivariate
1014 * polynomial in Q[x]. The product of the three parts is the polynomial
1017 * @param x main variable
1018 * @param u unit part (returned)
1019 * @param c content part (returned)
1020 * @param p primitive part (returned)
1021 * @see ex::unit, ex::content, ex::primpart */
1022 void ex::unitcontprim(const ex &x, ex &u, ex &c, ex &p) const
1024 // Quick check for zero (avoid expanding)
1031 // Special case: input is a number
1032 if (is_exactly_a<numeric>(*this)) {
1033 if (info(info_flags::negative)) {
1035 c = abs(ex_to<numeric>(*this));
1044 // Expand input polynomial
1052 // Compute unit and content
1056 // Divide by unit and content to get primitive part
1061 if (is_exactly_a<numeric>(c))
1062 p = *this / (c * u);
1064 p = quo(e, c * u, x, false);
1069 * GCD of multivariate polynomials
1072 /** Compute GCD of multivariate polynomials using the subresultant PRS
1073 * algorithm. This function is used internally by gcd().
1075 * @param a first multivariate polynomial
1076 * @param b second multivariate polynomial
1077 * @param var iterator to first element of vector of sym_desc structs
1078 * @return the GCD as a new expression
1081 static ex sr_gcd(const ex &a, const ex &b, sym_desc_vec::const_iterator var)
1087 // The first symbol is our main variable
1088 const ex &x = var->sym;
1090 // Sort c and d so that c has higher degree
1092 int adeg = a.degree(x), bdeg = b.degree(x);
1106 // Remove content from c and d, to be attached to GCD later
1107 ex cont_c = c.content(x);
1108 ex cont_d = d.content(x);
1109 ex gamma = gcd(cont_c, cont_d, NULL, NULL, false);
1112 c = c.primpart(x, cont_c);
1113 d = d.primpart(x, cont_d);
1115 // First element of subresultant sequence
1116 ex r = _ex0, ri = _ex1, psi = _ex1;
1117 int delta = cdeg - ddeg;
1121 // Calculate polynomial pseudo-remainder
1122 r = prem(c, d, x, false);
1124 return gamma * d.primpart(x);
1128 if (!divide_in_z(r, ri * pow(psi, delta), d, var))
1129 throw(std::runtime_error("invalid expression in sr_gcd(), division failed"));
1132 if (is_exactly_a<numeric>(r))
1135 return gamma * r.primpart(x);
1138 // Next element of subresultant sequence
1139 ri = c.expand().lcoeff(x);
1143 divide_in_z(pow(ri, delta), pow(psi, delta-1), psi, var+1);
1144 delta = cdeg - ddeg;
1149 /** Return maximum (absolute value) coefficient of a polynomial.
1150 * This function is used internally by heur_gcd().
1152 * @return maximum coefficient
1154 numeric ex::max_coefficient() const
1156 return bp->max_coefficient();
1159 /** Implementation ex::max_coefficient().
1161 numeric basic::max_coefficient() const
1166 numeric numeric::max_coefficient() const
1171 numeric add::max_coefficient() const
1173 epvector::const_iterator it = seq.begin();
1174 epvector::const_iterator itend = seq.end();
1175 GINAC_ASSERT(is_exactly_a<numeric>(overall_coeff));
1176 numeric cur_max = abs(ex_to<numeric>(overall_coeff));
1177 while (it != itend) {
1179 GINAC_ASSERT(!is_exactly_a<numeric>(it->rest));
1180 a = abs(ex_to<numeric>(it->coeff));
1188 numeric mul::max_coefficient() const
1190 #ifdef DO_GINAC_ASSERT
1191 epvector::const_iterator it = seq.begin();
1192 epvector::const_iterator itend = seq.end();
1193 while (it != itend) {
1194 GINAC_ASSERT(!is_exactly_a<numeric>(recombine_pair_to_ex(*it)));
1197 #endif // def DO_GINAC_ASSERT
1198 GINAC_ASSERT(is_exactly_a<numeric>(overall_coeff));
1199 return abs(ex_to<numeric>(overall_coeff));
1203 /** Apply symmetric modular homomorphism to an expanded multivariate
1204 * polynomial. This function is usually used internally by heur_gcd().
1207 * @return mapped polynomial
1209 ex basic::smod(const numeric &xi) const
1214 ex numeric::smod(const numeric &xi) const
1216 return GiNaC::smod(*this, xi);
1219 ex add::smod(const numeric &xi) const
1222 newseq.reserve(seq.size()+1);
1223 epvector::const_iterator it = seq.begin();
1224 epvector::const_iterator itend = seq.end();
1225 while (it != itend) {
1226 GINAC_ASSERT(!is_exactly_a<numeric>(it->rest));
1227 numeric coeff = GiNaC::smod(ex_to<numeric>(it->coeff), xi);
1228 if (!coeff.is_zero())
1229 newseq.push_back(expair(it->rest, coeff));
1232 GINAC_ASSERT(is_exactly_a<numeric>(overall_coeff));
1233 numeric coeff = GiNaC::smod(ex_to<numeric>(overall_coeff), xi);
1234 return (new add(newseq,coeff))->setflag(status_flags::dynallocated);
1237 ex mul::smod(const numeric &xi) const
1239 #ifdef DO_GINAC_ASSERT
1240 epvector::const_iterator it = seq.begin();
1241 epvector::const_iterator itend = seq.end();
1242 while (it != itend) {
1243 GINAC_ASSERT(!is_exactly_a<numeric>(recombine_pair_to_ex(*it)));
1246 #endif // def DO_GINAC_ASSERT
1247 mul * mulcopyp = new mul(*this);
1248 GINAC_ASSERT(is_exactly_a<numeric>(overall_coeff));
1249 mulcopyp->overall_coeff = GiNaC::smod(ex_to<numeric>(overall_coeff),xi);
1250 mulcopyp->clearflag(status_flags::evaluated);
1251 mulcopyp->clearflag(status_flags::hash_calculated);
1252 return mulcopyp->setflag(status_flags::dynallocated);
1256 /** xi-adic polynomial interpolation */
1257 static ex interpolate(const ex &gamma, const numeric &xi, const ex &x, int degree_hint = 1)
1259 exvector g; g.reserve(degree_hint);
1261 numeric rxi = xi.inverse();
1262 for (int i=0; !e.is_zero(); i++) {
1264 g.push_back(gi * power(x, i));
1267 return (new add(g))->setflag(status_flags::dynallocated);
1270 /** Exception thrown by heur_gcd() to signal failure. */
1271 class gcdheu_failed {};
1273 /** Compute GCD of multivariate polynomials using the heuristic GCD algorithm.
1274 * get_symbol_stats() must have been called previously with the input
1275 * polynomials and an iterator to the first element of the sym_desc vector
1276 * passed in. This function is used internally by gcd().
1278 * @param a first integer multivariate polynomial (expanded)
1279 * @param b second integer multivariate polynomial (expanded)
1280 * @param ca cofactor of polynomial a (returned), NULL to suppress
1281 * calculation of cofactor
1282 * @param cb cofactor of polynomial b (returned), NULL to suppress
1283 * calculation of cofactor
1284 * @param var iterator to first element of vector of sym_desc structs
1285 * @param res the GCD (returned)
1286 * @return true if GCD was computed, false otherwise.
1288 * @exception gcdheu_failed() */
1289 static bool heur_gcd_z(ex& res, const ex &a, const ex &b, ex *ca, ex *cb,
1290 sym_desc_vec::const_iterator var)
1296 // Algorithm only works for non-vanishing input polynomials
1297 if (a.is_zero() || b.is_zero())
1300 // GCD of two numeric values -> CLN
1301 if (is_exactly_a<numeric>(a) && is_exactly_a<numeric>(b)) {
1302 numeric g = gcd(ex_to<numeric>(a), ex_to<numeric>(b));
1304 *ca = ex_to<numeric>(a) / g;
1306 *cb = ex_to<numeric>(b) / g;
1311 // The first symbol is our main variable
1312 const ex &x = var->sym;
1314 // Remove integer content
1315 numeric gc = gcd(a.integer_content(), b.integer_content());
1316 numeric rgc = gc.inverse();
1319 int maxdeg = std::max(p.degree(x), q.degree(x));
1321 // Find evaluation point
1322 numeric mp = p.max_coefficient();
1323 numeric mq = q.max_coefficient();
1326 xi = mq * (*_num2_p) + (*_num2_p);
1328 xi = mp * (*_num2_p) + (*_num2_p);
1331 for (int t=0; t<6; t++) {
1332 if (xi.int_length() * maxdeg > 100000) {
1333 throw gcdheu_failed();
1336 // Apply evaluation homomorphism and calculate GCD
1339 bool found = heur_gcd_z(gamma,
1340 p.subs(x == xi, subs_options::no_pattern),
1341 q.subs(x == xi, subs_options::no_pattern),
1344 gamma = gamma.expand();
1345 // Reconstruct polynomial from GCD of mapped polynomials
1346 ex g = interpolate(gamma, xi, x, maxdeg);
1348 // Remove integer content
1349 g /= g.integer_content();
1351 // If the calculated polynomial divides both p and q, this is the GCD
1353 if (divide_in_z(p, g, ca ? *ca : dummy, var) && divide_in_z(q, g, cb ? *cb : dummy, var)) {
1360 // Next evaluation point
1361 xi = iquo(xi * isqrt(isqrt(xi)) * numeric(73794), numeric(27011));
1366 /** Compute GCD of multivariate polynomials using the heuristic GCD algorithm.
1367 * get_symbol_stats() must have been called previously with the input
1368 * polynomials and an iterator to the first element of the sym_desc vector
1369 * passed in. This function is used internally by gcd().
1371 * @param a first rational multivariate polynomial (expanded)
1372 * @param b second rational multivariate polynomial (expanded)
1373 * @param ca cofactor of polynomial a (returned), NULL to suppress
1374 * calculation of cofactor
1375 * @param cb cofactor of polynomial b (returned), NULL to suppress
1376 * calculation of cofactor
1377 * @param var iterator to first element of vector of sym_desc structs
1378 * @param res the GCD (returned)
1379 * @return true if GCD was computed, false otherwise.
1383 static bool heur_gcd(ex& res, const ex& a, const ex& b, ex *ca, ex *cb,
1384 sym_desc_vec::const_iterator var)
1386 if (a.info(info_flags::integer_polynomial) &&
1387 b.info(info_flags::integer_polynomial)) {
1389 return heur_gcd_z(res, a, b, ca, cb, var);
1390 } catch (gcdheu_failed) {
1395 // convert polynomials to Z[X]
1396 const numeric a_lcm = lcm_of_coefficients_denominators(a);
1397 const numeric ab_lcm = lcmcoeff(b, a_lcm);
1399 const ex ai = a*ab_lcm;
1400 const ex bi = b*ab_lcm;
1401 if (!ai.info(info_flags::integer_polynomial))
1402 throw std::logic_error("heur_gcd: not an integer polynomial [1]");
1404 if (!bi.info(info_flags::integer_polynomial))
1405 throw std::logic_error("heur_gcd: not an integer polynomial [2]");
1409 found = heur_gcd_z(res, ai, bi, ca, cb, var);
1410 } catch (gcdheu_failed) {
1414 // GCD is not unique, it's defined up to a unit (i.e. invertible
1415 // element). If the coefficient ring is a field, every its element is
1416 // invertible, so one can multiply the polynomial GCD with any element
1417 // of the coefficient field. We use this ambiguity to make cofactors
1418 // integer polynomials.
1425 // gcd helper to handle partially factored polynomials (to avoid expanding
1426 // large expressions). At least one of the arguments should be a power.
1427 static ex gcd_pf_pow(const ex& a, const ex& b, ex* ca, ex* cb);
1429 // gcd helper to handle partially factored polynomials (to avoid expanding
1430 // large expressions). At least one of the arguments should be a product.
1431 static ex gcd_pf_mul(const ex& a, const ex& b, ex* ca, ex* cb);
1433 /** Compute GCD (Greatest Common Divisor) of multivariate polynomials a(X)
1434 * and b(X) in Z[X]. Optionally also compute the cofactors of a and b,
1435 * defined by a = ca * gcd(a, b) and b = cb * gcd(a, b).
1437 * @param a first multivariate polynomial
1438 * @param b second multivariate polynomial
1439 * @param ca pointer to expression that will receive the cofactor of a, or NULL
1440 * @param cb pointer to expression that will receive the cofactor of b, or NULL
1441 * @param check_args check whether a and b are polynomials with rational
1442 * coefficients (defaults to "true")
1443 * @return the GCD as a new expression */
1444 ex gcd(const ex &a, const ex &b, ex *ca, ex *cb, bool check_args, unsigned options)
1450 // GCD of numerics -> CLN
1451 if (is_exactly_a<numeric>(a) && is_exactly_a<numeric>(b)) {
1452 numeric g = gcd(ex_to<numeric>(a), ex_to<numeric>(b));
1461 *ca = ex_to<numeric>(a) / g;
1463 *cb = ex_to<numeric>(b) / g;
1470 if (check_args && (!a.info(info_flags::rational_polynomial) || !b.info(info_flags::rational_polynomial))) {
1471 throw(std::invalid_argument("gcd: arguments must be polynomials over the rationals"));
1474 // Partially factored cases (to avoid expanding large expressions)
1475 if (!(options & gcd_options::no_part_factored)) {
1476 if (is_exactly_a<mul>(a) || is_exactly_a<mul>(b))
1477 return gcd_pf_mul(a, b, ca, cb);
1479 if (is_exactly_a<power>(a) || is_exactly_a<power>(b))
1480 return gcd_pf_pow(a, b, ca, cb);
1484 // Some trivial cases
1485 ex aex = a.expand(), bex = b.expand();
1486 if (aex.is_zero()) {
1493 if (bex.is_zero()) {
1500 if (aex.is_equal(_ex1) || bex.is_equal(_ex1)) {
1508 if (a.is_equal(b)) {
1517 if (is_a<symbol>(aex)) {
1518 if (! bex.subs(aex==_ex0, subs_options::no_pattern).is_zero()) {
1527 if (is_a<symbol>(bex)) {
1528 if (! aex.subs(bex==_ex0, subs_options::no_pattern).is_zero()) {
1537 if (is_exactly_a<numeric>(aex)) {
1538 numeric bcont = bex.integer_content();
1539 numeric g = gcd(ex_to<numeric>(aex), bcont);
1541 *ca = ex_to<numeric>(aex)/g;
1547 if (is_exactly_a<numeric>(bex)) {
1548 numeric acont = aex.integer_content();
1549 numeric g = gcd(ex_to<numeric>(bex), acont);
1553 *cb = ex_to<numeric>(bex)/g;
1557 // Gather symbol statistics
1558 sym_desc_vec sym_stats;
1559 get_symbol_stats(a, b, sym_stats);
1561 // The symbol with least degree which is contained in both polynomials
1562 // is our main variable
1563 sym_desc_vec::iterator vari = sym_stats.begin();
1564 while ((vari != sym_stats.end()) &&
1565 (((vari->ldeg_b == 0) && (vari->deg_b == 0)) ||
1566 ((vari->ldeg_a == 0) && (vari->deg_a == 0))))
1569 // No common symbols at all, just return 1:
1570 if (vari == sym_stats.end()) {
1571 // N.B: keep cofactors factored
1578 // move symbols which contained only in one of the polynomials
1580 rotate(sym_stats.begin(), vari, sym_stats.end());
1582 sym_desc_vec::const_iterator var = sym_stats.begin();
1583 const ex &x = var->sym;
1585 // Cancel trivial common factor
1586 int ldeg_a = var->ldeg_a;
1587 int ldeg_b = var->ldeg_b;
1588 int min_ldeg = std::min(ldeg_a,ldeg_b);
1590 ex common = power(x, min_ldeg);
1591 return gcd((aex / common).expand(), (bex / common).expand(), ca, cb, false) * common;
1594 // Try to eliminate variables
1595 if (var->deg_a == 0 && var->deg_b != 0 ) {
1596 ex bex_u, bex_c, bex_p;
1597 bex.unitcontprim(x, bex_u, bex_c, bex_p);
1598 ex g = gcd(aex, bex_c, ca, cb, false);
1600 *cb *= bex_u * bex_p;
1602 } else if (var->deg_b == 0 && var->deg_a != 0) {
1603 ex aex_u, aex_c, aex_p;
1604 aex.unitcontprim(x, aex_u, aex_c, aex_p);
1605 ex g = gcd(aex_c, bex, ca, cb, false);
1607 *ca *= aex_u * aex_p;
1611 // Try heuristic algorithm first, fall back to PRS if that failed
1613 if (!(options & gcd_options::no_heur_gcd)) {
1614 bool found = heur_gcd(g, aex, bex, ca, cb, var);
1616 // heur_gcd have already computed cofactors...
1617 if (g.is_equal(_ex1)) {
1618 // ... but we want to keep them factored if possible.
1632 if (options & gcd_options::use_sr_gcd) {
1633 g = sr_gcd(aex, bex, var);
1636 for (std::size_t n = sym_stats.size(); n-- != 0; )
1637 vars.push_back(sym_stats[n].sym);
1638 g = chinrem_gcd(aex, bex, vars);
1641 if (g.is_equal(_ex1)) {
1642 // Keep cofactors factored if possible
1649 divide(aex, g, *ca, false);
1651 divide(bex, g, *cb, false);
1656 // gcd helper to handle partially factored polynomials (to avoid expanding
1657 // large expressions). Both arguments should be powers.
1658 static ex gcd_pf_pow_pow(const ex& a, const ex& b, ex* ca, ex* cb)
1661 const ex& exp_a = a.op(1);
1663 const ex& exp_b = b.op(1);
1665 // a = p^n, b = p^m, gcd = p^min(n, m)
1666 if (p.is_equal(pb)) {
1667 if (exp_a < exp_b) {
1671 *cb = power(p, exp_b - exp_a);
1672 return power(p, exp_a);
1675 *ca = power(p, exp_a - exp_b);
1678 return power(p, exp_b);
1683 ex p_gcd = gcd(p, pb, &p_co, &pb_co, false);
1684 // a(x) = p(x)^n, b(x) = p_b(x)^m, gcd (p, p_b) = 1 ==> gcd(a,b) = 1
1685 if (p_gcd.is_equal(_ex1)) {
1691 // XXX: do I need to check for p_gcd = -1?
1694 // there are common factors:
1695 // a(x) = g(x)^n A(x)^n, b(x) = g(x)^m B(x)^m ==>
1696 // gcd(a, b) = g(x)^n gcd(A(x)^n, g(x)^(n-m) B(x)^m
1697 if (exp_a < exp_b) {
1698 ex pg = gcd(power(p_co, exp_a), power(p_gcd, exp_b-exp_a)*power(pb_co, exp_b), ca, cb, false);
1699 return power(p_gcd, exp_a)*pg;
1701 ex pg = gcd(power(p_gcd, exp_a - exp_b)*power(p_co, exp_a), power(pb_co, exp_b), ca, cb, false);
1702 return power(p_gcd, exp_b)*pg;
1706 static ex gcd_pf_pow(const ex& a, const ex& b, ex* ca, ex* cb)
1708 if (is_exactly_a<power>(a) && is_exactly_a<power>(b))
1709 return gcd_pf_pow_pow(a, b, ca, cb);
1711 if (is_exactly_a<power>(b) && (! is_exactly_a<power>(a)))
1712 return gcd_pf_pow(b, a, cb, ca);
1714 GINAC_ASSERT(is_exactly_a<power>(a));
1717 const ex& exp_a = a.op(1);
1718 if (p.is_equal(b)) {
1719 // a = p^n, b = p, gcd = p
1721 *ca = power(p, a.op(1) - 1);
1728 ex p_gcd = gcd(p, b, &p_co, &bpart_co, false);
1730 // a(x) = p(x)^n, gcd(p, b) = 1 ==> gcd(a, b) = 1
1731 if (p_gcd.is_equal(_ex1)) {
1738 // 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))
1739 ex rg = gcd(power(p_gcd, exp_a-1)*power(p_co, exp_a), bpart_co, ca, cb, false);
1743 static ex gcd_pf_mul(const ex& a, const ex& b, ex* ca, ex* cb)
1745 if (is_exactly_a<mul>(a) && is_exactly_a<mul>(b)
1746 && (b.nops() > a.nops()))
1747 return gcd_pf_mul(b, a, cb, ca);
1749 if (is_exactly_a<mul>(b) && (!is_exactly_a<mul>(a)))
1750 return gcd_pf_mul(b, a, cb, ca);
1752 GINAC_ASSERT(is_exactly_a<mul>(a));
1753 size_t num = a.nops();
1754 exvector g; g.reserve(num);
1755 exvector acc_ca; acc_ca.reserve(num);
1757 for (size_t i=0; i<num; i++) {
1758 ex part_ca, part_cb;
1759 g.push_back(gcd(a.op(i), part_b, &part_ca, &part_cb, false));
1760 acc_ca.push_back(part_ca);
1764 *ca = (new mul(acc_ca))->setflag(status_flags::dynallocated);
1767 return (new mul(g))->setflag(status_flags::dynallocated);
1770 /** Compute LCM (Least Common Multiple) of multivariate polynomials in Z[X].
1772 * @param a first multivariate polynomial
1773 * @param b second multivariate polynomial
1774 * @param check_args check whether a and b are polynomials with rational
1775 * coefficients (defaults to "true")
1776 * @return the LCM as a new expression */
1777 ex lcm(const ex &a, const ex &b, bool check_args)
1779 if (is_exactly_a<numeric>(a) && is_exactly_a<numeric>(b))
1780 return lcm(ex_to<numeric>(a), ex_to<numeric>(b));
1781 if (check_args && (!a.info(info_flags::rational_polynomial) || !b.info(info_flags::rational_polynomial)))
1782 throw(std::invalid_argument("lcm: arguments must be polynomials over the rationals"));
1785 ex g = gcd(a, b, &ca, &cb, false);
1791 * Square-free factorization
1794 /** Compute square-free factorization of multivariate polynomial a(x) using
1795 * Yun's algorithm. Used internally by sqrfree().
1797 * @param a multivariate polynomial over Z[X], treated here as univariate
1798 * polynomial in x (needs not be expanded).
1799 * @param x variable to factor in
1800 * @return vector of factors sorted in ascending degree */
1801 static exvector sqrfree_yun(const ex &a, const symbol &x)
1810 if (g.is_equal(_ex1)) {
1824 } while (!z.is_zero());
1829 /** Compute a square-free factorization of a multivariate polynomial in Q[X].
1831 * @param a multivariate polynomial over Q[X] (needs not be expanded)
1832 * @param l lst of variables to factor in, may be left empty for autodetection
1833 * @return a square-free factorization of \p a.
1836 * A polynomial \f$p(X) \in C[X]\f$ is said <EM>square-free</EM>
1837 * if, whenever any two polynomials \f$q(X)\f$ and \f$r(X)\f$
1840 * p(X) = q(X)^2 r(X),
1842 * we have \f$q(X) \in C\f$.
1843 * This means that \f$p(X)\f$ has no repeated factors, apart
1844 * eventually from constants.
1845 * Given a polynomial \f$p(X) \in C[X]\f$, we say that the
1848 * p(X) = b \cdot p_1(X)^{a_1} \cdot p_2(X)^{a_2} \cdots p_r(X)^{a_r}
1850 * is a <EM>square-free factorization</EM> of \f$p(X)\f$ if the
1851 * following conditions hold:
1852 * -# \f$b \in C\f$ and \f$b \neq 0\f$;
1853 * -# \f$a_i\f$ is a positive integer for \f$i = 1, \ldots, r\f$;
1854 * -# the degree of the polynomial \f$p_i\f$ is strictly positive
1855 * for \f$i = 1, \ldots, r\f$;
1856 * -# the polynomial \f$\Pi_{i=1}^r p_i(X)\f$ is square-free.
1858 * Square-free factorizations need not be unique. For example, if
1859 * \f$a_i\f$ is even, we could change the polynomial \f$p_i(X)\f$
1860 * into \f$-p_i(X)\f$.
1861 * Observe also that the factors \f$p_i(X)\f$ need not be irreducible
1864 ex sqrfree(const ex &a, const lst &l)
1866 if (is_exactly_a<numeric>(a) ||
1867 is_a<symbol>(a)) // shortcuts
1870 // If no lst of variables to factorize in was specified we have to
1871 // invent one now. Maybe one can optimize here by reversing the order
1872 // or so, I don't know.
1876 get_symbol_stats(a, _ex0, sdv);
1877 sym_desc_vec::const_iterator it = sdv.begin(), itend = sdv.end();
1878 while (it != itend) {
1879 args.append(it->sym);
1886 // Find the symbol to factor in at this stage
1887 if (!is_a<symbol>(args.op(0)))
1888 throw (std::runtime_error("sqrfree(): invalid factorization variable"));
1889 const symbol &x = ex_to<symbol>(args.op(0));
1891 // convert the argument from something in Q[X] to something in Z[X]
1892 const numeric lcm = lcm_of_coefficients_denominators(a);
1893 const ex tmp = multiply_lcm(a,lcm);
1896 exvector factors = sqrfree_yun(tmp, x);
1898 // construct the next list of symbols with the first element popped
1900 newargs.remove_first();
1902 // recurse down the factors in remaining variables
1903 if (newargs.nops()>0) {
1904 exvector::iterator i = factors.begin();
1905 while (i != factors.end()) {
1906 *i = sqrfree(*i, newargs);
1911 // Done with recursion, now construct the final result
1913 exvector::const_iterator it = factors.begin(), itend = factors.end();
1914 for (int p = 1; it!=itend; ++it, ++p)
1915 result *= power(*it, p);
1917 // Yun's algorithm does not account for constant factors. (For univariate
1918 // polynomials it works only in the monic case.) We can correct this by
1919 // inserting what has been lost back into the result. For completeness
1920 // we'll also have to recurse down that factor in the remaining variables.
1921 if (newargs.nops()>0)
1922 result *= sqrfree(quo(tmp, result, x), newargs);
1924 result *= quo(tmp, result, x);
1926 // Put in the rational overall factor again and return
1927 return result * lcm.inverse();
1931 /** Compute square-free partial fraction decomposition of rational function
1934 * @param a rational function over Z[x], treated as univariate polynomial
1936 * @param x variable to factor in
1937 * @return decomposed rational function */
1938 ex sqrfree_parfrac(const ex & a, const symbol & x)
1940 // Find numerator and denominator
1941 ex nd = numer_denom(a);
1942 ex numer = nd.op(0), denom = nd.op(1);
1943 //clog << "numer = " << numer << ", denom = " << denom << endl;
1945 // Convert N(x)/D(x) -> Q(x) + R(x)/D(x), so degree(R) < degree(D)
1946 ex red_poly = quo(numer, denom, x), red_numer = rem(numer, denom, x).expand();
1947 //clog << "red_poly = " << red_poly << ", red_numer = " << red_numer << endl;
1949 // Factorize denominator and compute cofactors
1950 exvector yun = sqrfree_yun(denom, x);
1951 //clog << "yun factors: " << exprseq(yun) << endl;
1952 size_t num_yun = yun.size();
1953 exvector factor; factor.reserve(num_yun);
1954 exvector cofac; cofac.reserve(num_yun);
1955 for (size_t i=0; i<num_yun; i++) {
1956 if (!yun[i].is_equal(_ex1)) {
1957 for (size_t j=0; j<=i; j++) {
1958 factor.push_back(pow(yun[i], j+1));
1960 for (size_t k=0; k<num_yun; k++) {
1962 prod *= pow(yun[k], i-j);
1964 prod *= pow(yun[k], k+1);
1966 cofac.push_back(prod.expand());
1970 size_t num_factors = factor.size();
1971 //clog << "factors : " << exprseq(factor) << endl;
1972 //clog << "cofactors: " << exprseq(cofac) << endl;
1974 // Construct coefficient matrix for decomposition
1975 int max_denom_deg = denom.degree(x);
1976 matrix sys(max_denom_deg + 1, num_factors);
1977 matrix rhs(max_denom_deg + 1, 1);
1978 for (int i=0; i<=max_denom_deg; i++) {
1979 for (size_t j=0; j<num_factors; j++)
1980 sys(i, j) = cofac[j].coeff(x, i);
1981 rhs(i, 0) = red_numer.coeff(x, i);
1983 //clog << "coeffs: " << sys << endl;
1984 //clog << "rhs : " << rhs << endl;
1986 // Solve resulting linear system
1987 matrix vars(num_factors, 1);
1988 for (size_t i=0; i<num_factors; i++)
1989 vars(i, 0) = symbol();
1990 matrix sol = sys.solve(vars, rhs);
1992 // Sum up decomposed fractions
1994 for (size_t i=0; i<num_factors; i++)
1995 sum += sol(i, 0) / factor[i];
1997 return red_poly + sum;
2002 * Normal form of rational functions
2006 * Note: The internal normal() functions (= basic::normal() and overloaded
2007 * functions) all return lists of the form {numerator, denominator}. This
2008 * is to get around mul::eval()'s automatic expansion of numeric coefficients.
2009 * E.g. (a+b)/3 is automatically converted to a/3+b/3 but we want to keep
2010 * the information that (a+b) is the numerator and 3 is the denominator.
2014 /** Create a symbol for replacing the expression "e" (or return a previously
2015 * assigned symbol). The symbol and expression are appended to repl, for
2016 * a later application of subs().
2017 * @see ex::normal */
2018 static ex replace_with_symbol(const ex & e, exmap & repl, exmap & rev_lookup)
2020 // Since the repl contains replaced expressions we should search for them
2021 ex e_replaced = e.subs(repl, subs_options::no_pattern);
2023 // Expression already replaced? Then return the assigned symbol
2024 exmap::const_iterator it = rev_lookup.find(e_replaced);
2025 if (it != rev_lookup.end())
2028 // Otherwise create new symbol and add to list, taking care that the
2029 // replacement expression doesn't itself contain symbols from repl,
2030 // because subs() is not recursive
2031 ex es = (new symbol)->setflag(status_flags::dynallocated);
2032 repl.insert(std::make_pair(es, e_replaced));
2033 rev_lookup.insert(std::make_pair(e_replaced, es));
2037 /** Create a symbol for replacing the expression "e" (or return a previously
2038 * assigned symbol). The symbol and expression are appended to repl, and the
2039 * symbol is returned.
2040 * @see basic::to_rational
2041 * @see basic::to_polynomial */
2042 static ex replace_with_symbol(const ex & e, exmap & repl)
2044 // Since the repl contains replaced expressions we should search for them
2045 ex e_replaced = e.subs(repl, subs_options::no_pattern);
2047 // Expression already replaced? Then return the assigned symbol
2048 for (exmap::const_iterator it = repl.begin(); it != repl.end(); ++it)
2049 if (it->second.is_equal(e_replaced))
2052 // Otherwise create new symbol and add to list, taking care that the
2053 // replacement expression doesn't itself contain symbols from repl,
2054 // because subs() is not recursive
2055 ex es = (new symbol)->setflag(status_flags::dynallocated);
2056 repl.insert(std::make_pair(es, e_replaced));
2061 /** Function object to be applied by basic::normal(). */
2062 struct normal_map_function : public map_function {
2064 normal_map_function(int l) : level(l) {}
2065 ex operator()(const ex & e) { return normal(e, level); }
2068 /** Default implementation of ex::normal(). It normalizes the children and
2069 * replaces the object with a temporary symbol.
2070 * @see ex::normal */
2071 ex basic::normal(exmap & repl, exmap & rev_lookup, int level) const
2074 return (new lst(replace_with_symbol(*this, repl, rev_lookup), _ex1))->setflag(status_flags::dynallocated);
2077 return (new lst(replace_with_symbol(*this, repl, rev_lookup), _ex1))->setflag(status_flags::dynallocated);
2078 else if (level == -max_recursion_level)
2079 throw(std::runtime_error("max recursion level reached"));
2081 normal_map_function map_normal(level - 1);
2082 return (new lst(replace_with_symbol(map(map_normal), repl, rev_lookup), _ex1))->setflag(status_flags::dynallocated);
2088 /** Implementation of ex::normal() for symbols. This returns the unmodified symbol.
2089 * @see ex::normal */
2090 ex symbol::normal(exmap & repl, exmap & rev_lookup, int level) const
2092 return (new lst(*this, _ex1))->setflag(status_flags::dynallocated);
2096 /** Implementation of ex::normal() for a numeric. It splits complex numbers
2097 * into re+I*im and replaces I and non-rational real numbers with a temporary
2099 * @see ex::normal */
2100 ex numeric::normal(exmap & repl, exmap & rev_lookup, int level) const
2102 numeric num = numer();
2105 if (num.is_real()) {
2106 if (!num.is_integer())
2107 numex = replace_with_symbol(numex, repl, rev_lookup);
2109 numeric re = num.real(), im = num.imag();
2110 ex re_ex = re.is_rational() ? re : replace_with_symbol(re, repl, rev_lookup);
2111 ex im_ex = im.is_rational() ? im : replace_with_symbol(im, repl, rev_lookup);
2112 numex = re_ex + im_ex * replace_with_symbol(I, repl, rev_lookup);
2115 // Denominator is always a real integer (see numeric::denom())
2116 return (new lst(numex, denom()))->setflag(status_flags::dynallocated);
2120 /** Fraction cancellation.
2121 * @param n numerator
2122 * @param d denominator
2123 * @return cancelled fraction {n, d} as a list */
2124 static ex frac_cancel(const ex &n, const ex &d)
2128 numeric pre_factor = *_num1_p;
2130 //std::clog << "frac_cancel num = " << num << ", den = " << den << std::endl;
2132 // Handle trivial case where denominator is 1
2133 if (den.is_equal(_ex1))
2134 return (new lst(num, den))->setflag(status_flags::dynallocated);
2136 // Handle special cases where numerator or denominator is 0
2138 return (new lst(num, _ex1))->setflag(status_flags::dynallocated);
2139 if (den.expand().is_zero())
2140 throw(std::overflow_error("frac_cancel: division by zero in frac_cancel"));
2142 // Bring numerator and denominator to Z[X] by multiplying with
2143 // LCM of all coefficients' denominators
2144 numeric num_lcm = lcm_of_coefficients_denominators(num);
2145 numeric den_lcm = lcm_of_coefficients_denominators(den);
2146 num = multiply_lcm(num, num_lcm);
2147 den = multiply_lcm(den, den_lcm);
2148 pre_factor = den_lcm / num_lcm;
2150 // Cancel GCD from numerator and denominator
2152 if (gcd(num, den, &cnum, &cden, false) != _ex1) {
2157 // Make denominator unit normal (i.e. coefficient of first symbol
2158 // as defined by get_first_symbol() is made positive)
2159 if (is_exactly_a<numeric>(den)) {
2160 if (ex_to<numeric>(den).is_negative()) {
2166 if (get_first_symbol(den, x)) {
2167 GINAC_ASSERT(is_exactly_a<numeric>(den.unit(x)));
2168 if (ex_to<numeric>(den.unit(x)).is_negative()) {
2175 // Return result as list
2176 //std::clog << " returns num = " << num << ", den = " << den << ", pre_factor = " << pre_factor << std::endl;
2177 return (new lst(num * pre_factor.numer(), den * pre_factor.denom()))->setflag(status_flags::dynallocated);
2181 /** Implementation of ex::normal() for a sum. It expands terms and performs
2182 * fractional addition.
2183 * @see ex::normal */
2184 ex add::normal(exmap & repl, exmap & rev_lookup, int level) const
2187 return (new lst(replace_with_symbol(*this, repl, rev_lookup), _ex1))->setflag(status_flags::dynallocated);
2188 else if (level == -max_recursion_level)
2189 throw(std::runtime_error("max recursion level reached"));
2191 // Normalize children and split each one into numerator and denominator
2192 exvector nums, dens;
2193 nums.reserve(seq.size()+1);
2194 dens.reserve(seq.size()+1);
2195 epvector::const_iterator it = seq.begin(), itend = seq.end();
2196 while (it != itend) {
2197 ex n = ex_to<basic>(recombine_pair_to_ex(*it)).normal(repl, rev_lookup, level-1);
2198 nums.push_back(n.op(0));
2199 dens.push_back(n.op(1));
2202 ex n = ex_to<numeric>(overall_coeff).normal(repl, rev_lookup, level-1);
2203 nums.push_back(n.op(0));
2204 dens.push_back(n.op(1));
2205 GINAC_ASSERT(nums.size() == dens.size());
2207 // Now, nums is a vector of all numerators and dens is a vector of
2209 //std::clog << "add::normal uses " << nums.size() << " summands:\n";
2211 // Add fractions sequentially
2212 exvector::const_iterator num_it = nums.begin(), num_itend = nums.end();
2213 exvector::const_iterator den_it = dens.begin(), den_itend = dens.end();
2214 //std::clog << " num = " << *num_it << ", den = " << *den_it << std::endl;
2215 ex num = *num_it++, den = *den_it++;
2216 while (num_it != num_itend) {
2217 //std::clog << " num = " << *num_it << ", den = " << *den_it << std::endl;
2218 ex next_num = *num_it++, next_den = *den_it++;
2220 // Trivially add sequences of fractions with identical denominators
2221 while ((den_it != den_itend) && next_den.is_equal(*den_it)) {
2222 next_num += *num_it;
2226 // Addition of two fractions, taking advantage of the fact that
2227 // the heuristic GCD algorithm computes the cofactors at no extra cost
2228 ex co_den1, co_den2;
2229 ex g = gcd(den, next_den, &co_den1, &co_den2, false);
2230 num = ((num * co_den2) + (next_num * co_den1)).expand();
2231 den *= co_den2; // this is the lcm(den, next_den)
2233 //std::clog << " common denominator = " << den << std::endl;
2235 // Cancel common factors from num/den
2236 return frac_cancel(num, den);
2240 /** Implementation of ex::normal() for a product. It cancels common factors
2242 * @see ex::normal() */
2243 ex mul::normal(exmap & repl, exmap & rev_lookup, int level) const
2246 return (new lst(replace_with_symbol(*this, repl, rev_lookup), _ex1))->setflag(status_flags::dynallocated);
2247 else if (level == -max_recursion_level)
2248 throw(std::runtime_error("max recursion level reached"));
2250 // Normalize children, separate into numerator and denominator
2251 exvector num; num.reserve(seq.size());
2252 exvector den; den.reserve(seq.size());
2254 epvector::const_iterator it = seq.begin(), itend = seq.end();
2255 while (it != itend) {
2256 n = ex_to<basic>(recombine_pair_to_ex(*it)).normal(repl, rev_lookup, level-1);
2257 num.push_back(n.op(0));
2258 den.push_back(n.op(1));
2261 n = ex_to<numeric>(overall_coeff).normal(repl, rev_lookup, level-1);
2262 num.push_back(n.op(0));
2263 den.push_back(n.op(1));
2265 // Perform fraction cancellation
2266 return frac_cancel((new mul(num))->setflag(status_flags::dynallocated),
2267 (new mul(den))->setflag(status_flags::dynallocated));
2271 /** Implementation of ex::normal([B) for powers. It normalizes the basis,
2272 * distributes integer exponents to numerator and denominator, and replaces
2273 * non-integer powers by temporary symbols.
2274 * @see ex::normal */
2275 ex power::normal(exmap & repl, exmap & rev_lookup, int level) const
2278 return (new lst(replace_with_symbol(*this, repl, rev_lookup), _ex1))->setflag(status_flags::dynallocated);
2279 else if (level == -max_recursion_level)
2280 throw(std::runtime_error("max recursion level reached"));
2282 // Normalize basis and exponent (exponent gets reassembled)
2283 ex n_basis = ex_to<basic>(basis).normal(repl, rev_lookup, level-1);
2284 ex n_exponent = ex_to<basic>(exponent).normal(repl, rev_lookup, level-1);
2285 n_exponent = n_exponent.op(0) / n_exponent.op(1);
2287 if (n_exponent.info(info_flags::integer)) {
2289 if (n_exponent.info(info_flags::positive)) {
2291 // (a/b)^n -> {a^n, b^n}
2292 return (new lst(power(n_basis.op(0), n_exponent), power(n_basis.op(1), n_exponent)))->setflag(status_flags::dynallocated);
2294 } else if (n_exponent.info(info_flags::negative)) {
2296 // (a/b)^-n -> {b^n, a^n}
2297 return (new lst(power(n_basis.op(1), -n_exponent), power(n_basis.op(0), -n_exponent)))->setflag(status_flags::dynallocated);
2302 if (n_exponent.info(info_flags::positive)) {
2304 // (a/b)^x -> {sym((a/b)^x), 1}
2305 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);
2307 } else if (n_exponent.info(info_flags::negative)) {
2309 if (n_basis.op(1).is_equal(_ex1)) {
2311 // a^-x -> {1, sym(a^x)}
2312 return (new lst(_ex1, replace_with_symbol(power(n_basis.op(0), -n_exponent), repl, rev_lookup)))->setflag(status_flags::dynallocated);
2316 // (a/b)^-x -> {sym((b/a)^x), 1}
2317 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);
2322 // (a/b)^x -> {sym((a/b)^x, 1}
2323 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);
2327 /** Implementation of ex::normal() for pseries. It normalizes each coefficient
2328 * and replaces the series by a temporary symbol.
2329 * @see ex::normal */
2330 ex pseries::normal(exmap & repl, exmap & rev_lookup, int level) const
2333 epvector::const_iterator i = seq.begin(), end = seq.end();
2335 ex restexp = i->rest.normal();
2336 if (!restexp.is_zero())
2337 newseq.push_back(expair(restexp, i->coeff));
2340 ex n = pseries(relational(var,point), newseq);
2341 return (new lst(replace_with_symbol(n, repl, rev_lookup), _ex1))->setflag(status_flags::dynallocated);
2345 /** Normalization of rational functions.
2346 * This function converts an expression to its normal form
2347 * "numerator/denominator", where numerator and denominator are (relatively
2348 * prime) polynomials. Any subexpressions which are not rational functions
2349 * (like non-rational numbers, non-integer powers or functions like sin(),
2350 * cos() etc.) are replaced by temporary symbols which are re-substituted by
2351 * the (normalized) subexpressions before normal() returns (this way, any
2352 * expression can be treated as a rational function). normal() is applied
2353 * recursively to arguments of functions etc.
2355 * @param level maximum depth of recursion
2356 * @return normalized expression */
2357 ex ex::normal(int level) const
2359 exmap repl, rev_lookup;
2361 ex e = bp->normal(repl, rev_lookup, level);
2362 GINAC_ASSERT(is_a<lst>(e));
2364 // Re-insert replaced symbols
2366 e = e.subs(repl, subs_options::no_pattern);
2368 // Convert {numerator, denominator} form back to fraction
2369 return e.op(0) / e.op(1);
2372 /** Get numerator of an expression. If the expression is not of the normal
2373 * form "numerator/denominator", it is first converted to this form and
2374 * then the numerator is returned.
2377 * @return numerator */
2378 ex ex::numer() const
2380 exmap repl, rev_lookup;
2382 ex e = bp->normal(repl, rev_lookup, 0);
2383 GINAC_ASSERT(is_a<lst>(e));
2385 // Re-insert replaced symbols
2389 return e.op(0).subs(repl, subs_options::no_pattern);
2392 /** Get denominator of an expression. If the expression is not of the normal
2393 * form "numerator/denominator", it is first converted to this form and
2394 * then the denominator is returned.
2397 * @return denominator */
2398 ex ex::denom() const
2400 exmap repl, rev_lookup;
2402 ex e = bp->normal(repl, rev_lookup, 0);
2403 GINAC_ASSERT(is_a<lst>(e));
2405 // Re-insert replaced symbols
2409 return e.op(1).subs(repl, subs_options::no_pattern);
2412 /** Get numerator and denominator of an expression. If the expression is not
2413 * of the normal form "numerator/denominator", it is first converted to this
2414 * form and then a list [numerator, denominator] is returned.
2417 * @return a list [numerator, denominator] */
2418 ex ex::numer_denom() const
2420 exmap repl, rev_lookup;
2422 ex e = bp->normal(repl, rev_lookup, 0);
2423 GINAC_ASSERT(is_a<lst>(e));
2425 // Re-insert replaced symbols
2429 return e.subs(repl, subs_options::no_pattern);
2433 /** Rationalization of non-rational functions.
2434 * This function converts a general expression to a rational function
2435 * by replacing all non-rational subexpressions (like non-rational numbers,
2436 * non-integer powers or functions like sin(), cos() etc.) to temporary
2437 * symbols. This makes it possible to use functions like gcd() and divide()
2438 * on non-rational functions by applying to_rational() on the arguments,
2439 * calling the desired function and re-substituting the temporary symbols
2440 * in the result. To make the last step possible, all temporary symbols and
2441 * their associated expressions are collected in the map specified by the
2442 * repl parameter, ready to be passed as an argument to ex::subs().
2444 * @param repl collects all temporary symbols and their replacements
2445 * @return rationalized expression */
2446 ex ex::to_rational(exmap & repl) const
2448 return bp->to_rational(repl);
2451 // GiNaC 1.1 compatibility function
2452 ex ex::to_rational(lst & repl_lst) const
2454 // Convert lst to exmap
2456 for (lst::const_iterator it = repl_lst.begin(); it != repl_lst.end(); ++it)
2457 m.insert(std::make_pair(it->op(0), it->op(1)));
2459 ex ret = bp->to_rational(m);
2461 // Convert exmap back to lst
2462 repl_lst.remove_all();
2463 for (exmap::const_iterator it = m.begin(); it != m.end(); ++it)
2464 repl_lst.append(it->first == it->second);
2469 ex ex::to_polynomial(exmap & repl) const
2471 return bp->to_polynomial(repl);
2474 // GiNaC 1.1 compatibility function
2475 ex ex::to_polynomial(lst & repl_lst) const
2477 // Convert lst to exmap
2479 for (lst::const_iterator it = repl_lst.begin(); it != repl_lst.end(); ++it)
2480 m.insert(std::make_pair(it->op(0), it->op(1)));
2482 ex ret = bp->to_polynomial(m);
2484 // Convert exmap back to lst
2485 repl_lst.remove_all();
2486 for (exmap::const_iterator it = m.begin(); it != m.end(); ++it)
2487 repl_lst.append(it->first == it->second);
2492 /** Default implementation of ex::to_rational(). This replaces the object with
2493 * a temporary symbol. */
2494 ex basic::to_rational(exmap & repl) const
2496 return replace_with_symbol(*this, repl);
2499 ex basic::to_polynomial(exmap & repl) const
2501 return replace_with_symbol(*this, repl);
2505 /** Implementation of ex::to_rational() for symbols. This returns the
2506 * unmodified symbol. */
2507 ex symbol::to_rational(exmap & repl) const
2512 /** Implementation of ex::to_polynomial() for symbols. This returns the
2513 * unmodified symbol. */
2514 ex symbol::to_polynomial(exmap & repl) const
2520 /** Implementation of ex::to_rational() for a numeric. It splits complex
2521 * numbers into re+I*im and replaces I and non-rational real numbers with a
2522 * temporary symbol. */
2523 ex numeric::to_rational(exmap & repl) const
2527 return replace_with_symbol(*this, repl);
2529 numeric re = real();
2530 numeric im = imag();
2531 ex re_ex = re.is_rational() ? re : replace_with_symbol(re, repl);
2532 ex im_ex = im.is_rational() ? im : replace_with_symbol(im, repl);
2533 return re_ex + im_ex * replace_with_symbol(I, repl);
2538 /** Implementation of ex::to_polynomial() for a numeric. It splits complex
2539 * numbers into re+I*im and replaces I and non-integer real numbers with a
2540 * temporary symbol. */
2541 ex numeric::to_polynomial(exmap & repl) const
2545 return replace_with_symbol(*this, repl);
2547 numeric re = real();
2548 numeric im = imag();
2549 ex re_ex = re.is_integer() ? re : replace_with_symbol(re, repl);
2550 ex im_ex = im.is_integer() ? im : replace_with_symbol(im, repl);
2551 return re_ex + im_ex * replace_with_symbol(I, repl);
2557 /** Implementation of ex::to_rational() for powers. It replaces non-integer
2558 * powers by temporary symbols. */
2559 ex power::to_rational(exmap & repl) const
2561 if (exponent.info(info_flags::integer))
2562 return power(basis.to_rational(repl), exponent);
2564 return replace_with_symbol(*this, repl);
2567 /** Implementation of ex::to_polynomial() for powers. It replaces non-posint
2568 * powers by temporary symbols. */
2569 ex power::to_polynomial(exmap & repl) const
2571 if (exponent.info(info_flags::posint))
2572 return power(basis.to_rational(repl), exponent);
2573 else if (exponent.info(info_flags::negint))
2575 ex basis_pref = collect_common_factors(basis);
2576 if (is_exactly_a<mul>(basis_pref) || is_exactly_a<power>(basis_pref)) {
2577 // (A*B)^n will be automagically transformed to A^n*B^n
2578 ex t = power(basis_pref, exponent);
2579 return t.to_polynomial(repl);
2582 return power(replace_with_symbol(power(basis, _ex_1), repl), -exponent);
2585 return replace_with_symbol(*this, repl);
2589 /** Implementation of ex::to_rational() for expairseqs. */
2590 ex expairseq::to_rational(exmap & repl) const
2593 s.reserve(seq.size());
2594 epvector::const_iterator i = seq.begin(), end = seq.end();
2596 s.push_back(split_ex_to_pair(recombine_pair_to_ex(*i).to_rational(repl)));
2599 ex oc = overall_coeff.to_rational(repl);
2600 if (oc.info(info_flags::numeric))
2601 return thisexpairseq(s, overall_coeff);
2603 s.push_back(combine_ex_with_coeff_to_pair(oc, _ex1));
2604 return thisexpairseq(s, default_overall_coeff());
2607 /** Implementation of ex::to_polynomial() for expairseqs. */
2608 ex expairseq::to_polynomial(exmap & repl) const
2611 s.reserve(seq.size());
2612 epvector::const_iterator i = seq.begin(), end = seq.end();
2614 s.push_back(split_ex_to_pair(recombine_pair_to_ex(*i).to_polynomial(repl)));
2617 ex oc = overall_coeff.to_polynomial(repl);
2618 if (oc.info(info_flags::numeric))
2619 return thisexpairseq(s, overall_coeff);
2621 s.push_back(combine_ex_with_coeff_to_pair(oc, _ex1));
2622 return thisexpairseq(s, default_overall_coeff());
2626 /** Remove the common factor in the terms of a sum 'e' by calculating the GCD,
2627 * and multiply it into the expression 'factor' (which needs to be initialized
2628 * to 1, unless you're accumulating factors). */
2629 static ex find_common_factor(const ex & e, ex & factor, exmap & repl)
2631 if (is_exactly_a<add>(e)) {
2633 size_t num = e.nops();
2634 exvector terms; terms.reserve(num);
2637 // Find the common GCD
2638 for (size_t i=0; i<num; i++) {
2639 ex x = e.op(i).to_polynomial(repl);
2641 if (is_exactly_a<add>(x) || is_exactly_a<mul>(x) || is_a<power>(x)) {
2643 x = find_common_factor(x, f, repl);
2655 if (gc.is_equal(_ex1))
2658 // The GCD is the factor we pull out
2661 // Now divide all terms by the GCD
2662 for (size_t i=0; i<num; i++) {
2665 // Try to avoid divide() because it expands the polynomial
2667 if (is_exactly_a<mul>(t)) {
2668 for (size_t j=0; j<t.nops(); j++) {
2669 if (t.op(j).is_equal(gc)) {
2670 exvector v; v.reserve(t.nops());
2671 for (size_t k=0; k<t.nops(); k++) {
2675 v.push_back(t.op(k));
2677 t = (new mul(v))->setflag(status_flags::dynallocated);
2687 return (new add(terms))->setflag(status_flags::dynallocated);
2689 } else if (is_exactly_a<mul>(e)) {
2691 size_t num = e.nops();
2692 exvector v; v.reserve(num);
2694 for (size_t i=0; i<num; i++)
2695 v.push_back(find_common_factor(e.op(i), factor, repl));
2697 return (new mul(v))->setflag(status_flags::dynallocated);
2699 } else if (is_exactly_a<power>(e)) {
2700 const ex e_exp(e.op(1));
2701 if (e_exp.info(info_flags::integer)) {
2702 ex eb = e.op(0).to_polynomial(repl);
2703 ex factor_local(_ex1);
2704 ex pre_res = find_common_factor(eb, factor_local, repl);
2705 factor *= power(factor_local, e_exp);
2706 return power(pre_res, e_exp);
2709 return e.to_polynomial(repl);
2716 /** Collect common factors in sums. This converts expressions like
2717 * 'a*(b*x+b*y)' to 'a*b*(x+y)'. */
2718 ex collect_common_factors(const ex & e)
2720 if (is_exactly_a<add>(e) || is_exactly_a<mul>(e) || is_exactly_a<power>(e)) {
2724 ex r = find_common_factor(e, factor, repl);
2725 return factor.subs(repl, subs_options::no_pattern) * r.subs(repl, subs_options::no_pattern);
2732 /** Resultant of two expressions e1,e2 with respect to symbol s.
2733 * Method: Compute determinant of Sylvester matrix of e1,e2,s. */
2734 ex resultant(const ex & e1, const ex & e2, const ex & s)
2736 const ex ee1 = e1.expand();
2737 const ex ee2 = e2.expand();
2738 if (!ee1.info(info_flags::polynomial) ||
2739 !ee2.info(info_flags::polynomial))
2740 throw(std::runtime_error("resultant(): arguments must be polynomials"));
2742 const int h1 = ee1.degree(s);
2743 const int l1 = ee1.ldegree(s);
2744 const int h2 = ee2.degree(s);
2745 const int l2 = ee2.ldegree(s);
2747 const int msize = h1 + h2;
2748 matrix m(msize, msize);
2750 for (int l = h1; l >= l1; --l) {
2751 const ex e = ee1.coeff(s, l);
2752 for (int k = 0; k < h2; ++k)
2755 for (int l = h2; l >= l2; --l) {
2756 const ex e = ee2.coeff(s, l);
2757 for (int k = 0; k < h1; ++k)
2758 m(k+h2, k+h2-l) = e;
2761 return m.determinant();
2765 } // namespace GiNaC