1 /** @file inifcns.cpp
2 *
3 * Implementation of GiNaC's initially known functions. */
4
5 /*
6 * GiNaC Copyright (C) 1999-2022 Johannes Gutenberg University Mainz, Germany
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
12 *
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
17 *
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 */
22
23 #include "inifcns.h"
24 #include "ex.h"
25 #include "constant.h"
26 #include "lst.h"
27 #include "fderivative.h"
28 #include "matrix.h"
29 #include "mul.h"
30 #include "power.h"
31 #include "operators.h"
32 #include "relational.h"
33 #include "pseries.h"
34 #include "symbol.h"
35 #include "symmetry.h"
36 #include "utils.h"
37
38 #include <stdexcept>
39 #include <vector>
40
41 namespace GiNaC {
42
43 //////////
44 // complex conjugate
45 //////////
46
conjugate_evalf(const ex & arg)47 static ex conjugate_evalf(const ex & arg)
48 {
49 if (is_exactly_a<numeric>(arg)) {
50 return ex_to<numeric>(arg).conjugate();
51 }
52 return conjugate_function(arg).hold();
53 }
54
conjugate_eval(const ex & arg)55 static ex conjugate_eval(const ex & arg)
56 {
57 return arg.conjugate();
58 }
59
conjugate_print_latex(const ex & arg,const print_context & c)60 static void conjugate_print_latex(const ex & arg, const print_context & c)
61 {
62 c.s << "\\bar{"; arg.print(c); c.s << "}";
63 }
64
conjugate_conjugate(const ex & arg)65 static ex conjugate_conjugate(const ex & arg)
66 {
67 return arg;
68 }
69
70 // If x is real then U.diff(x)-I*V.diff(x) represents both conjugate(U+I*V).diff(x)
71 // and conjugate((U+I*V).diff(x))
conjugate_expl_derivative(const ex & arg,const symbol & s)72 static ex conjugate_expl_derivative(const ex & arg, const symbol & s)
73 {
74 if (s.info(info_flags::real))
75 return conjugate(arg.diff(s));
76 else {
77 exvector vec_arg;
78 vec_arg.push_back(arg);
79 return fderivative(ex_to<function>(conjugate(arg)).get_serial(),0,vec_arg).hold()*arg.diff(s);
80 }
81 }
82
conjugate_real_part(const ex & arg)83 static ex conjugate_real_part(const ex & arg)
84 {
85 return arg.real_part();
86 }
87
conjugate_imag_part(const ex & arg)88 static ex conjugate_imag_part(const ex & arg)
89 {
90 return -arg.imag_part();
91 }
92
func_arg_info(const ex & arg,unsigned inf)93 static bool func_arg_info(const ex & arg, unsigned inf)
94 {
95 // for some functions we can return the info() of its argument
96 // (think of conjugate())
97 switch (inf) {
98 case info_flags::polynomial:
99 case info_flags::integer_polynomial:
100 case info_flags::cinteger_polynomial:
101 case info_flags::rational_polynomial:
102 case info_flags::real:
103 case info_flags::rational:
104 case info_flags::integer:
105 case info_flags::crational:
106 case info_flags::cinteger:
107 case info_flags::even:
108 case info_flags::odd:
109 case info_flags::prime:
110 case info_flags::crational_polynomial:
111 case info_flags::rational_function:
112 case info_flags::positive:
113 case info_flags::negative:
114 case info_flags::nonnegative:
115 case info_flags::posint:
116 case info_flags::negint:
117 case info_flags::nonnegint:
118 case info_flags::has_indices:
119 return arg.info(inf);
120 }
121 return false;
122 }
123
conjugate_info(const ex & arg,unsigned inf)124 static bool conjugate_info(const ex & arg, unsigned inf)
125 {
126 return func_arg_info(arg, inf);
127 }
128
129 REGISTER_FUNCTION(conjugate_function, eval_func(conjugate_eval).
130 evalf_func(conjugate_evalf).
131 expl_derivative_func(conjugate_expl_derivative).
132 info_func(conjugate_info).
133 print_func<print_latex>(conjugate_print_latex).
134 conjugate_func(conjugate_conjugate).
135 real_part_func(conjugate_real_part).
136 imag_part_func(conjugate_imag_part).
137 set_name("conjugate","conjugate"));
138
139 //////////
140 // real part
141 //////////
142
real_part_evalf(const ex & arg)143 static ex real_part_evalf(const ex & arg)
144 {
145 if (is_exactly_a<numeric>(arg)) {
146 return ex_to<numeric>(arg).real();
147 }
148 return real_part_function(arg).hold();
149 }
150
real_part_eval(const ex & arg)151 static ex real_part_eval(const ex & arg)
152 {
153 return arg.real_part();
154 }
155
real_part_print_latex(const ex & arg,const print_context & c)156 static void real_part_print_latex(const ex & arg, const print_context & c)
157 {
158 c.s << "\\Re"; arg.print(c); c.s << "";
159 }
160
real_part_conjugate(const ex & arg)161 static ex real_part_conjugate(const ex & arg)
162 {
163 return real_part_function(arg).hold();
164 }
165
real_part_real_part(const ex & arg)166 static ex real_part_real_part(const ex & arg)
167 {
168 return real_part_function(arg).hold();
169 }
170
real_part_imag_part(const ex & arg)171 static ex real_part_imag_part(const ex & arg)
172 {
173 return 0;
174 }
175
176 // If x is real then Re(e).diff(x) is equal to Re(e.diff(x))
real_part_expl_derivative(const ex & arg,const symbol & s)177 static ex real_part_expl_derivative(const ex & arg, const symbol & s)
178 {
179 if (s.info(info_flags::real))
180 return real_part_function(arg.diff(s));
181 else {
182 exvector vec_arg;
183 vec_arg.push_back(arg);
184 return fderivative(ex_to<function>(real_part(arg)).get_serial(),0,vec_arg).hold()*arg.diff(s);
185 }
186 }
187
188 REGISTER_FUNCTION(real_part_function, eval_func(real_part_eval).
189 evalf_func(real_part_evalf).
190 expl_derivative_func(real_part_expl_derivative).
191 print_func<print_latex>(real_part_print_latex).
192 conjugate_func(real_part_conjugate).
193 real_part_func(real_part_real_part).
194 imag_part_func(real_part_imag_part).
195 set_name("real_part","real_part"));
196
197 //////////
198 // imag part
199 //////////
200
imag_part_evalf(const ex & arg)201 static ex imag_part_evalf(const ex & arg)
202 {
203 if (is_exactly_a<numeric>(arg)) {
204 return ex_to<numeric>(arg).imag();
205 }
206 return imag_part_function(arg).hold();
207 }
208
imag_part_eval(const ex & arg)209 static ex imag_part_eval(const ex & arg)
210 {
211 return arg.imag_part();
212 }
213
imag_part_print_latex(const ex & arg,const print_context & c)214 static void imag_part_print_latex(const ex & arg, const print_context & c)
215 {
216 c.s << "\\Im"; arg.print(c); c.s << "";
217 }
218
imag_part_conjugate(const ex & arg)219 static ex imag_part_conjugate(const ex & arg)
220 {
221 return imag_part_function(arg).hold();
222 }
223
imag_part_real_part(const ex & arg)224 static ex imag_part_real_part(const ex & arg)
225 {
226 return imag_part_function(arg).hold();
227 }
228
imag_part_imag_part(const ex & arg)229 static ex imag_part_imag_part(const ex & arg)
230 {
231 return 0;
232 }
233
234 // If x is real then Im(e).diff(x) is equal to Im(e.diff(x))
imag_part_expl_derivative(const ex & arg,const symbol & s)235 static ex imag_part_expl_derivative(const ex & arg, const symbol & s)
236 {
237 if (s.info(info_flags::real))
238 return imag_part_function(arg.diff(s));
239 else {
240 exvector vec_arg;
241 vec_arg.push_back(arg);
242 return fderivative(ex_to<function>(imag_part(arg)).get_serial(),0,vec_arg).hold()*arg.diff(s);
243 }
244 }
245
246 REGISTER_FUNCTION(imag_part_function, eval_func(imag_part_eval).
247 evalf_func(imag_part_evalf).
248 expl_derivative_func(imag_part_expl_derivative).
249 print_func<print_latex>(imag_part_print_latex).
250 conjugate_func(imag_part_conjugate).
251 real_part_func(imag_part_real_part).
252 imag_part_func(imag_part_imag_part).
253 set_name("imag_part","imag_part"));
254
255 //////////
256 // absolute value
257 //////////
258
abs_evalf(const ex & arg)259 static ex abs_evalf(const ex & arg)
260 {
261 if (is_exactly_a<numeric>(arg))
262 return abs(ex_to<numeric>(arg));
263
264 return abs(arg).hold();
265 }
266
abs_eval(const ex & arg)267 static ex abs_eval(const ex & arg)
268 {
269 if (is_exactly_a<numeric>(arg))
270 return abs(ex_to<numeric>(arg));
271
272 if (arg.info(info_flags::nonnegative))
273 return arg;
274
275 if (arg.info(info_flags::negative) || (-arg).info(info_flags::nonnegative))
276 return -arg;
277
278 if (is_ex_the_function(arg, abs))
279 return arg;
280
281 if (is_ex_the_function(arg, exp))
282 return exp(arg.op(0).real_part());
283
284 if (is_exactly_a<power>(arg)) {
285 const ex& base = arg.op(0);
286 const ex& exponent = arg.op(1);
287 if (base.info(info_flags::positive) || exponent.info(info_flags::real))
288 return pow(abs(base), exponent.real_part());
289 }
290
291 if (is_ex_the_function(arg, conjugate_function))
292 return abs(arg.op(0));
293
294 if (is_ex_the_function(arg, step))
295 return arg;
296
297 return abs(arg).hold();
298 }
299
abs_expand(const ex & arg,unsigned options)300 static ex abs_expand(const ex & arg, unsigned options)
301 {
302 if ((options & expand_options::expand_transcendental)
303 && is_exactly_a<mul>(arg)) {
304 exvector prodseq;
305 prodseq.reserve(arg.nops());
306 for (const_iterator i = arg.begin(); i != arg.end(); ++i) {
307 if (options & expand_options::expand_function_args)
308 prodseq.push_back(abs(i->expand(options)));
309 else
310 prodseq.push_back(abs(*i));
311 }
312 return dynallocate<mul>(prodseq).setflag(status_flags::expanded);
313 }
314
315 if (options & expand_options::expand_function_args)
316 return abs(arg.expand(options)).hold();
317 else
318 return abs(arg).hold();
319 }
320
abs_expl_derivative(const ex & arg,const symbol & s)321 static ex abs_expl_derivative(const ex & arg, const symbol & s)
322 {
323 ex diff_arg = arg.diff(s);
324 return (diff_arg*arg.conjugate()+arg*diff_arg.conjugate())/2/abs(arg);
325 }
326
abs_print_latex(const ex & arg,const print_context & c)327 static void abs_print_latex(const ex & arg, const print_context & c)
328 {
329 c.s << "{|"; arg.print(c); c.s << "|}";
330 }
331
abs_print_csrc_float(const ex & arg,const print_context & c)332 static void abs_print_csrc_float(const ex & arg, const print_context & c)
333 {
334 c.s << "fabs("; arg.print(c); c.s << ")";
335 }
336
abs_conjugate(const ex & arg)337 static ex abs_conjugate(const ex & arg)
338 {
339 return abs(arg).hold();
340 }
341
abs_real_part(const ex & arg)342 static ex abs_real_part(const ex & arg)
343 {
344 return abs(arg).hold();
345 }
346
abs_imag_part(const ex & arg)347 static ex abs_imag_part(const ex& arg)
348 {
349 return 0;
350 }
351
abs_power(const ex & arg,const ex & exp)352 static ex abs_power(const ex & arg, const ex & exp)
353 {
354 if ((is_a<numeric>(exp) && ex_to<numeric>(exp).is_even()) || exp.info(info_flags::even)) {
355 if (arg.info(info_flags::real) || arg.is_equal(arg.conjugate()))
356 return pow(arg, exp);
357 else
358 return pow(arg, exp/2) * pow(arg.conjugate(), exp/2);
359 } else
360 return power(abs(arg), exp).hold();
361 }
362
abs_info(const ex & arg,unsigned inf)363 bool abs_info(const ex & arg, unsigned inf)
364 {
365 switch (inf) {
366 case info_flags::integer:
367 case info_flags::even:
368 case info_flags::odd:
369 case info_flags::prime:
370 return arg.info(inf);
371 case info_flags::nonnegint:
372 return arg.info(info_flags::integer);
373 case info_flags::nonnegative:
374 case info_flags::real:
375 return true;
376 case info_flags::negative:
377 return false;
378 case info_flags::positive:
379 return arg.info(info_flags::positive) || arg.info(info_flags::negative);
380 case info_flags::has_indices: {
381 if (arg.info(info_flags::has_indices))
382 return true;
383 else
384 return false;
385 }
386 }
387 return false;
388 }
389
390 REGISTER_FUNCTION(abs, eval_func(abs_eval).
391 evalf_func(abs_evalf).
392 expand_func(abs_expand).
393 expl_derivative_func(abs_expl_derivative).
394 info_func(abs_info).
395 print_func<print_latex>(abs_print_latex).
396 print_func<print_csrc_float>(abs_print_csrc_float).
397 print_func<print_csrc_double>(abs_print_csrc_float).
398 conjugate_func(abs_conjugate).
399 real_part_func(abs_real_part).
400 imag_part_func(abs_imag_part).
401 power_func(abs_power));
402
403 //////////
404 // Step function
405 //////////
406
step_evalf(const ex & arg)407 static ex step_evalf(const ex & arg)
408 {
409 if (is_exactly_a<numeric>(arg))
410 return step(ex_to<numeric>(arg));
411
412 return step(arg).hold();
413 }
414
step_eval(const ex & arg)415 static ex step_eval(const ex & arg)
416 {
417 if (is_exactly_a<numeric>(arg))
418 return step(ex_to<numeric>(arg));
419
420 else if (is_exactly_a<mul>(arg) &&
421 is_exactly_a<numeric>(arg.op(arg.nops()-1))) {
422 numeric oc = ex_to<numeric>(arg.op(arg.nops()-1));
423 if (oc.is_real()) {
424 if (oc > 0)
425 // step(42*x) -> step(x)
426 return step(arg/oc).hold();
427 else
428 // step(-42*x) -> step(-x)
429 return step(-arg/oc).hold();
430 }
431 if (oc.real().is_zero()) {
432 if (oc.imag() > 0)
433 // step(42*I*x) -> step(I*x)
434 return step(I*arg/oc).hold();
435 else
436 // step(-42*I*x) -> step(-I*x)
437 return step(-I*arg/oc).hold();
438 }
439 }
440
441 return step(arg).hold();
442 }
443
step_series(const ex & arg,const relational & rel,int order,unsigned options)444 static ex step_series(const ex & arg,
445 const relational & rel,
446 int order,
447 unsigned options)
448 {
449 const ex arg_pt = arg.subs(rel, subs_options::no_pattern);
450 if (arg_pt.info(info_flags::numeric)
451 && ex_to<numeric>(arg_pt).real().is_zero()
452 && !(options & series_options::suppress_branchcut))
453 throw (std::domain_error("step_series(): on imaginary axis"));
454
455 epvector seq { expair(step(arg_pt), _ex0) };
456 return pseries(rel, std::move(seq));
457 }
458
step_conjugate(const ex & arg)459 static ex step_conjugate(const ex& arg)
460 {
461 return step(arg).hold();
462 }
463
step_real_part(const ex & arg)464 static ex step_real_part(const ex& arg)
465 {
466 return step(arg).hold();
467 }
468
step_imag_part(const ex & arg)469 static ex step_imag_part(const ex& arg)
470 {
471 return 0;
472 }
473
474 REGISTER_FUNCTION(step, eval_func(step_eval).
475 evalf_func(step_evalf).
476 series_func(step_series).
477 conjugate_func(step_conjugate).
478 real_part_func(step_real_part).
479 imag_part_func(step_imag_part));
480
481 //////////
482 // Complex sign
483 //////////
484
csgn_evalf(const ex & arg)485 static ex csgn_evalf(const ex & arg)
486 {
487 if (is_exactly_a<numeric>(arg))
488 return csgn(ex_to<numeric>(arg));
489
490 return csgn(arg).hold();
491 }
492
csgn_eval(const ex & arg)493 static ex csgn_eval(const ex & arg)
494 {
495 if (is_exactly_a<numeric>(arg))
496 return csgn(ex_to<numeric>(arg));
497
498 else if (is_exactly_a<mul>(arg) &&
499 is_exactly_a<numeric>(arg.op(arg.nops()-1))) {
500 numeric oc = ex_to<numeric>(arg.op(arg.nops()-1));
501 if (oc.is_real()) {
502 if (oc > 0)
503 // csgn(42*x) -> csgn(x)
504 return csgn(arg/oc).hold();
505 else
506 // csgn(-42*x) -> -csgn(x)
507 return -csgn(arg/oc).hold();
508 }
509 if (oc.real().is_zero()) {
510 if (oc.imag() > 0)
511 // csgn(42*I*x) -> csgn(I*x)
512 return csgn(I*arg/oc).hold();
513 else
514 // csgn(-42*I*x) -> -csgn(I*x)
515 return -csgn(I*arg/oc).hold();
516 }
517 }
518
519 return csgn(arg).hold();
520 }
521
csgn_series(const ex & arg,const relational & rel,int order,unsigned options)522 static ex csgn_series(const ex & arg,
523 const relational & rel,
524 int order,
525 unsigned options)
526 {
527 const ex arg_pt = arg.subs(rel, subs_options::no_pattern);
528 if (arg_pt.info(info_flags::numeric)
529 && ex_to<numeric>(arg_pt).real().is_zero()
530 && !(options & series_options::suppress_branchcut))
531 throw (std::domain_error("csgn_series(): on imaginary axis"));
532
533 epvector seq { expair(csgn(arg_pt), _ex0) };
534 return pseries(rel, std::move(seq));
535 }
536
csgn_conjugate(const ex & arg)537 static ex csgn_conjugate(const ex& arg)
538 {
539 return csgn(arg).hold();
540 }
541
csgn_real_part(const ex & arg)542 static ex csgn_real_part(const ex& arg)
543 {
544 return csgn(arg).hold();
545 }
546
csgn_imag_part(const ex & arg)547 static ex csgn_imag_part(const ex& arg)
548 {
549 return 0;
550 }
551
csgn_power(const ex & arg,const ex & exp)552 static ex csgn_power(const ex & arg, const ex & exp)
553 {
554 if (is_a<numeric>(exp) && exp.info(info_flags::positive) && ex_to<numeric>(exp).is_integer()) {
555 if (ex_to<numeric>(exp).is_odd())
556 return csgn(arg).hold();
557 else
558 return power(csgn(arg), _ex2).hold();
559 } else
560 return power(csgn(arg), exp).hold();
561 }
562
563
564 REGISTER_FUNCTION(csgn, eval_func(csgn_eval).
565 evalf_func(csgn_evalf).
566 series_func(csgn_series).
567 conjugate_func(csgn_conjugate).
568 real_part_func(csgn_real_part).
569 imag_part_func(csgn_imag_part).
570 power_func(csgn_power));
571
572
573 //////////
574 // Eta function: eta(x,y) == log(x*y) - log(x) - log(y).
575 // This function is closely related to the unwinding number K, sometimes found
576 // in modern literature: K(z) == (z-log(exp(z)))/(2*Pi*I).
577 //////////
578
eta_evalf(const ex & x,const ex & y)579 static ex eta_evalf(const ex &x, const ex &y)
580 {
581 // It seems like we basically have to replicate the eval function here,
582 // since the expression might not be fully evaluated yet.
583 if (x.info(info_flags::positive) || y.info(info_flags::positive))
584 return _ex0;
585
586 if (x.info(info_flags::numeric) && y.info(info_flags::numeric)) {
587 const numeric nx = ex_to<numeric>(x);
588 const numeric ny = ex_to<numeric>(y);
589 const numeric nxy = ex_to<numeric>(x*y);
590 int cut = 0;
591 if (nx.is_real() && nx.is_negative())
592 cut -= 4;
593 if (ny.is_real() && ny.is_negative())
594 cut -= 4;
595 if (nxy.is_real() && nxy.is_negative())
596 cut += 4;
597 return evalf(I/4*Pi)*((csgn(-imag(nx))+1)*(csgn(-imag(ny))+1)*(csgn(imag(nxy))+1)-
598 (csgn(imag(nx))+1)*(csgn(imag(ny))+1)*(csgn(-imag(nxy))+1)+cut);
599 }
600
601 return eta(x,y).hold();
602 }
603
eta_eval(const ex & x,const ex & y)604 static ex eta_eval(const ex &x, const ex &y)
605 {
606 // trivial: eta(x,c) -> 0 if c is real and positive
607 if (x.info(info_flags::positive) || y.info(info_flags::positive))
608 return _ex0;
609
610 if (x.info(info_flags::numeric) && y.info(info_flags::numeric)) {
611 // don't call eta_evalf here because it would call Pi.evalf()!
612 const numeric nx = ex_to<numeric>(x);
613 const numeric ny = ex_to<numeric>(y);
614 const numeric nxy = ex_to<numeric>(x*y);
615 int cut = 0;
616 if (nx.is_real() && nx.is_negative())
617 cut -= 4;
618 if (ny.is_real() && ny.is_negative())
619 cut -= 4;
620 if (nxy.is_real() && nxy.is_negative())
621 cut += 4;
622 return (I/4)*Pi*((csgn(-imag(nx))+1)*(csgn(-imag(ny))+1)*(csgn(imag(nxy))+1)-
623 (csgn(imag(nx))+1)*(csgn(imag(ny))+1)*(csgn(-imag(nxy))+1)+cut);
624 }
625
626 return eta(x,y).hold();
627 }
628
eta_series(const ex & x,const ex & y,const relational & rel,int order,unsigned options)629 static ex eta_series(const ex & x, const ex & y,
630 const relational & rel,
631 int order,
632 unsigned options)
633 {
634 const ex x_pt = x.subs(rel, subs_options::no_pattern);
635 const ex y_pt = y.subs(rel, subs_options::no_pattern);
636 if ((x_pt.info(info_flags::numeric) && x_pt.info(info_flags::negative)) ||
637 (y_pt.info(info_flags::numeric) && y_pt.info(info_flags::negative)) ||
638 ((x_pt*y_pt).info(info_flags::numeric) && (x_pt*y_pt).info(info_flags::negative)))
639 throw (std::domain_error("eta_series(): on discontinuity"));
640 epvector seq { expair(eta(x_pt,y_pt), _ex0) };
641 return pseries(rel, std::move(seq));
642 }
643
eta_conjugate(const ex & x,const ex & y)644 static ex eta_conjugate(const ex & x, const ex & y)
645 {
646 return -eta(x, y).hold();
647 }
648
eta_real_part(const ex & x,const ex & y)649 static ex eta_real_part(const ex & x, const ex & y)
650 {
651 return 0;
652 }
653
eta_imag_part(const ex & x,const ex & y)654 static ex eta_imag_part(const ex & x, const ex & y)
655 {
656 return -I*eta(x, y).hold();
657 }
658
659 REGISTER_FUNCTION(eta, eval_func(eta_eval).
660 evalf_func(eta_evalf).
661 series_func(eta_series).
662 latex_name("\\eta").
663 set_symmetry(sy_symm(0, 1)).
664 conjugate_func(eta_conjugate).
665 real_part_func(eta_real_part).
666 imag_part_func(eta_imag_part));
667
668
669 //////////
670 // dilogarithm
671 //////////
672
Li2_evalf(const ex & x)673 static ex Li2_evalf(const ex & x)
674 {
675 if (is_exactly_a<numeric>(x))
676 return Li2(ex_to<numeric>(x));
677
678 return Li2(x).hold();
679 }
680
Li2_eval(const ex & x)681 static ex Li2_eval(const ex & x)
682 {
683 if (x.info(info_flags::numeric)) {
684 // Li2(0) -> 0
685 if (x.is_zero())
686 return _ex0;
687 // Li2(1) -> Pi^2/6
688 if (x.is_equal(_ex1))
689 return power(Pi,_ex2)/_ex6;
690 // Li2(1/2) -> Pi^2/12 - log(2)^2/2
691 if (x.is_equal(_ex1_2))
692 return power(Pi,_ex2)/_ex12 + power(log(_ex2),_ex2)*_ex_1_2;
693 // Li2(-1) -> -Pi^2/12
694 if (x.is_equal(_ex_1))
695 return -power(Pi,_ex2)/_ex12;
696 // Li2(I) -> -Pi^2/48+Catalan*I
697 if (x.is_equal(I))
698 return power(Pi,_ex2)/_ex_48 + Catalan*I;
699 // Li2(-I) -> -Pi^2/48-Catalan*I
700 if (x.is_equal(-I))
701 return power(Pi,_ex2)/_ex_48 - Catalan*I;
702 // Li2(float)
703 if (!x.info(info_flags::crational))
704 return Li2(ex_to<numeric>(x));
705 }
706
707 return Li2(x).hold();
708 }
709
Li2_deriv(const ex & x,unsigned deriv_param)710 static ex Li2_deriv(const ex & x, unsigned deriv_param)
711 {
712 GINAC_ASSERT(deriv_param==0);
713
714 // d/dx Li2(x) -> -log(1-x)/x
715 return -log(_ex1-x)/x;
716 }
717
Li2_series(const ex & x,const relational & rel,int order,unsigned options)718 static ex Li2_series(const ex &x, const relational &rel, int order, unsigned options)
719 {
720 const ex x_pt = x.subs(rel, subs_options::no_pattern);
721 if (x_pt.info(info_flags::numeric)) {
722 // First special case: x==0 (derivatives have poles)
723 if (x_pt.is_zero()) {
724 // method:
725 // The problem is that in d/dx Li2(x==0) == -log(1-x)/x we cannot
726 // simply substitute x==0. The limit, however, exists: it is 1.
727 // We also know all higher derivatives' limits:
728 // (d/dx)^n Li2(x) == n!/n^2.
729 // So the primitive series expansion is
730 // Li2(x==0) == x + x^2/4 + x^3/9 + ...
731 // and so on.
732 // We first construct such a primitive series expansion manually in
733 // a dummy symbol s and then insert the argument's series expansion
734 // for s. Reexpanding the resulting series returns the desired
735 // result.
736 const symbol s;
737 ex ser;
738 // manually construct the primitive expansion
739 for (int i=1; i<order; ++i)
740 ser += pow(s,i) / pow(numeric(i), *_num2_p);
741 // substitute the argument's series expansion
742 ser = ser.subs(s==x.series(rel, order), subs_options::no_pattern);
743 // maybe that was terminating, so add a proper order term
744 epvector nseq { expair(Order(_ex1), order) };
745 ser += pseries(rel, std::move(nseq));
746 // reexpanding it will collapse the series again
747 return ser.series(rel, order);
748 // NB: Of course, this still does not allow us to compute anything
749 // like sin(Li2(x)).series(x==0,2), since then this code here is
750 // not reached and the derivative of sin(Li2(x)) doesn't allow the
751 // substitution x==0. Probably limits *are* needed for the general
752 // cases. In case L'Hospital's rule is implemented for limits and
753 // basic::series() takes care of this, this whole block is probably
754 // obsolete!
755 }
756 // second special case: x==1 (branch point)
757 if (x_pt.is_equal(_ex1)) {
758 // method:
759 // construct series manually in a dummy symbol s
760 const symbol s;
761 ex ser = zeta(_ex2);
762 // manually construct the primitive expansion
763 for (int i=1; i<order; ++i)
764 ser += pow(1-s,i) * (numeric(1,i)*(I*Pi+log(s-1)) - numeric(1,i*i));
765 // substitute the argument's series expansion
766 ser = ser.subs(s==x.series(rel, order), subs_options::no_pattern);
767 // maybe that was terminating, so add a proper order term
768 epvector nseq { expair(Order(_ex1), order) };
769 ser += pseries(rel, std::move(nseq));
770 // reexpanding it will collapse the series again
771 return ser.series(rel, order);
772 }
773 // third special case: x real, >=1 (branch cut)
774 if (!(options & series_options::suppress_branchcut) &&
775 ex_to<numeric>(x_pt).is_real() && ex_to<numeric>(x_pt)>1) {
776 // method:
777 // This is the branch cut: assemble the primitive series manually
778 // and then add the corresponding complex step function.
779 const symbol &s = ex_to<symbol>(rel.lhs());
780 const ex point = rel.rhs();
781 const symbol foo;
782 epvector seq;
783 // zeroth order term:
784 seq.push_back(expair(Li2(x_pt), _ex0));
785 // compute the intermediate terms:
786 ex replarg = series(Li2(x), s==foo, order);
787 for (size_t i=1; i<replarg.nops()-1; ++i)
788 seq.push_back(expair((replarg.op(i)/power(s-foo,i)).series(foo==point,1,options).op(0).subs(foo==s, subs_options::no_pattern),i));
789 // append an order term:
790 seq.push_back(expair(Order(_ex1), replarg.nops()-1));
791 return pseries(rel, std::move(seq));
792 }
793 }
794 // all other cases should be safe, by now:
795 throw do_taylor(); // caught by function::series()
796 }
797
Li2_conjugate(const ex & x)798 static ex Li2_conjugate(const ex & x)
799 {
800 // conjugate(Li2(x))==Li2(conjugate(x)) unless on the branch cuts which
801 // run along the positive real axis beginning at 1.
802 if (x.info(info_flags::negative)) {
803 return Li2(x).hold();
804 }
805 if (is_exactly_a<numeric>(x) &&
806 (!x.imag_part().is_zero() || x < *_num1_p)) {
807 return Li2(x.conjugate());
808 }
809 return conjugate_function(Li2(x)).hold();
810 }
811
812 REGISTER_FUNCTION(Li2, eval_func(Li2_eval).
813 evalf_func(Li2_evalf).
814 derivative_func(Li2_deriv).
815 series_func(Li2_series).
816 conjugate_func(Li2_conjugate).
817 latex_name("\\mathrm{Li}_2"));
818
819 //////////
820 // trilogarithm
821 //////////
822
Li3_eval(const ex & x)823 static ex Li3_eval(const ex & x)
824 {
825 if (x.is_zero())
826 return x;
827 return Li3(x).hold();
828 }
829
830 REGISTER_FUNCTION(Li3, eval_func(Li3_eval).
831 latex_name("\\mathrm{Li}_3"));
832
833 //////////
834 // Derivatives of Riemann's Zeta-function zetaderiv(0,x)==zeta(x)
835 //////////
836
zetaderiv_eval(const ex & n,const ex & x)837 static ex zetaderiv_eval(const ex & n, const ex & x)
838 {
839 if (n.info(info_flags::numeric)) {
840 // zetaderiv(0,x) -> zeta(x)
841 if (n.is_zero())
842 return zeta(x).hold();
843 }
844
845 return zetaderiv(n, x).hold();
846 }
847
zetaderiv_deriv(const ex & n,const ex & x,unsigned deriv_param)848 static ex zetaderiv_deriv(const ex & n, const ex & x, unsigned deriv_param)
849 {
850 GINAC_ASSERT(deriv_param<2);
851
852 if (deriv_param==0) {
853 // d/dn zeta(n,x)
854 throw(std::logic_error("cannot diff zetaderiv(n,x) with respect to n"));
855 }
856 // d/dx psi(n,x)
857 return zetaderiv(n+1,x);
858 }
859
860 REGISTER_FUNCTION(zetaderiv, eval_func(zetaderiv_eval).
861 derivative_func(zetaderiv_deriv).
862 latex_name("\\zeta^\\prime"));
863
864 //////////
865 // factorial
866 //////////
867
factorial_evalf(const ex & x)868 static ex factorial_evalf(const ex & x)
869 {
870 return factorial(x).hold();
871 }
872
factorial_eval(const ex & x)873 static ex factorial_eval(const ex & x)
874 {
875 if (is_exactly_a<numeric>(x))
876 return factorial(ex_to<numeric>(x));
877 else
878 return factorial(x).hold();
879 }
880
factorial_print_dflt_latex(const ex & x,const print_context & c)881 static void factorial_print_dflt_latex(const ex & x, const print_context & c)
882 {
883 if (is_exactly_a<symbol>(x) ||
884 is_exactly_a<constant>(x) ||
885 is_exactly_a<function>(x)) {
886 x.print(c); c.s << "!";
887 } else {
888 c.s << "("; x.print(c); c.s << ")!";
889 }
890 }
891
factorial_conjugate(const ex & x)892 static ex factorial_conjugate(const ex & x)
893 {
894 return factorial(x).hold();
895 }
896
factorial_real_part(const ex & x)897 static ex factorial_real_part(const ex & x)
898 {
899 return factorial(x).hold();
900 }
901
factorial_imag_part(const ex & x)902 static ex factorial_imag_part(const ex & x)
903 {
904 return 0;
905 }
906
907 REGISTER_FUNCTION(factorial, eval_func(factorial_eval).
908 evalf_func(factorial_evalf).
909 print_func<print_dflt>(factorial_print_dflt_latex).
910 print_func<print_latex>(factorial_print_dflt_latex).
911 conjugate_func(factorial_conjugate).
912 real_part_func(factorial_real_part).
913 imag_part_func(factorial_imag_part));
914
915 //////////
916 // binomial
917 //////////
918
binomial_evalf(const ex & x,const ex & y)919 static ex binomial_evalf(const ex & x, const ex & y)
920 {
921 return binomial(x, y).hold();
922 }
923
binomial_sym(const ex & x,const numeric & y)924 static ex binomial_sym(const ex & x, const numeric & y)
925 {
926 if (y.is_integer()) {
927 if (y.is_nonneg_integer()) {
928 const unsigned N = y.to_int();
929 if (N == 0) return _ex1;
930 if (N == 1) return x;
931 ex t = x.expand();
932 for (unsigned i = 2; i <= N; ++i)
933 t = (t * (x + i - y - 1)).expand() / i;
934 return t;
935 } else
936 return _ex0;
937 }
938
939 return binomial(x, y).hold();
940 }
941
binomial_eval(const ex & x,const ex & y)942 static ex binomial_eval(const ex & x, const ex &y)
943 {
944 if (is_exactly_a<numeric>(y)) {
945 if (is_exactly_a<numeric>(x) && ex_to<numeric>(x).is_integer())
946 return binomial(ex_to<numeric>(x), ex_to<numeric>(y));
947 else
948 return binomial_sym(x, ex_to<numeric>(y));
949 } else
950 return binomial(x, y).hold();
951 }
952
953 // At the moment the numeric evaluation of a binomial function always
954 // gives a real number, but if this would be implemented using the gamma
955 // function, also complex conjugation should be changed (or rather, deleted).
binomial_conjugate(const ex & x,const ex & y)956 static ex binomial_conjugate(const ex & x, const ex & y)
957 {
958 return binomial(x,y).hold();
959 }
960
binomial_real_part(const ex & x,const ex & y)961 static ex binomial_real_part(const ex & x, const ex & y)
962 {
963 return binomial(x,y).hold();
964 }
965
binomial_imag_part(const ex & x,const ex & y)966 static ex binomial_imag_part(const ex & x, const ex & y)
967 {
968 return 0;
969 }
970
971 REGISTER_FUNCTION(binomial, eval_func(binomial_eval).
972 evalf_func(binomial_evalf).
973 conjugate_func(binomial_conjugate).
974 real_part_func(binomial_real_part).
975 imag_part_func(binomial_imag_part));
976
977 //////////
978 // Order term function (for truncated power series)
979 //////////
980
Order_eval(const ex & x)981 static ex Order_eval(const ex & x)
982 {
983 if (is_exactly_a<numeric>(x)) {
984 // O(c) -> O(1) or 0
985 if (!x.is_zero())
986 return Order(_ex1).hold();
987 else
988 return _ex0;
989 } else if (is_exactly_a<mul>(x)) {
990 const mul &m = ex_to<mul>(x);
991 // O(c*expr) -> O(expr)
992 if (is_exactly_a<numeric>(m.op(m.nops() - 1)))
993 return Order(x / m.op(m.nops() - 1)).hold();
994 }
995 return Order(x).hold();
996 }
997
Order_series(const ex & x,const relational & r,int order,unsigned options)998 static ex Order_series(const ex & x, const relational & r, int order, unsigned options)
999 {
1000 // Just wrap the function into a pseries object
1001 GINAC_ASSERT(is_a<symbol>(r.lhs()));
1002 const symbol &s = ex_to<symbol>(r.lhs());
1003 epvector new_seq { expair(Order(_ex1), numeric(std::min(x.ldegree(s), order))) };
1004 return pseries(r, std::move(new_seq));
1005 }
1006
Order_conjugate(const ex & x)1007 static ex Order_conjugate(const ex & x)
1008 {
1009 return Order(x).hold();
1010 }
1011
Order_real_part(const ex & x)1012 static ex Order_real_part(const ex & x)
1013 {
1014 return Order(x).hold();
1015 }
1016
Order_imag_part(const ex & x)1017 static ex Order_imag_part(const ex & x)
1018 {
1019 if(x.info(info_flags::real))
1020 return 0;
1021 return Order(x).hold();
1022 }
1023
Order_expl_derivative(const ex & arg,const symbol & s)1024 static ex Order_expl_derivative(const ex & arg, const symbol & s)
1025 {
1026 return Order(arg.diff(s));
1027 }
1028
1029 REGISTER_FUNCTION(Order, eval_func(Order_eval).
1030 series_func(Order_series).
1031 latex_name("\\mathcal{O}").
1032 expl_derivative_func(Order_expl_derivative).
1033 conjugate_func(Order_conjugate).
1034 real_part_func(Order_real_part).
1035 imag_part_func(Order_imag_part));
1036
1037 //////////
1038 // Solve linear system
1039 //////////
1040
1041 class symbolset {
1042 exset s;
insert_symbols(const ex & e)1043 void insert_symbols(const ex &e)
1044 {
1045 if (is_a<symbol>(e)) {
1046 s.insert(e);
1047 } else {
1048 for (const ex &sube : e) {
1049 insert_symbols(sube);
1050 }
1051 }
1052 }
1053 public:
symbolset(const ex & e)1054 explicit symbolset(const ex &e)
1055 {
1056 insert_symbols(e);
1057 }
has(const ex & e) const1058 bool has(const ex &e) const
1059 {
1060 return s.find(e) != s.end();
1061 }
1062 };
1063
lsolve(const ex & eqns,const ex & symbols,unsigned options)1064 ex lsolve(const ex &eqns, const ex &symbols, unsigned options)
1065 {
1066 // solve a system of linear equations
1067 if (eqns.info(info_flags::relation_equal)) {
1068 if (!symbols.info(info_flags::symbol))
1069 throw(std::invalid_argument("lsolve(): 2nd argument must be a symbol"));
1070 const ex sol = lsolve(lst{eqns}, lst{symbols});
1071
1072 GINAC_ASSERT(sol.nops()==1);
1073 GINAC_ASSERT(is_exactly_a<relational>(sol.op(0)));
1074
1075 return sol.op(0).op(1); // return rhs of first solution
1076 }
1077
1078 // syntax checks
1079 if (!(eqns.info(info_flags::list) || eqns.info(info_flags::exprseq))) {
1080 throw(std::invalid_argument("lsolve(): 1st argument must be a list, a sequence, or an equation"));
1081 }
1082 for (size_t i=0; i<eqns.nops(); i++) {
1083 if (!eqns.op(i).info(info_flags::relation_equal)) {
1084 throw(std::invalid_argument("lsolve(): 1st argument must be a list of equations"));
1085 }
1086 }
1087 if (!(symbols.info(info_flags::list) || symbols.info(info_flags::exprseq))) {
1088 throw(std::invalid_argument("lsolve(): 2nd argument must be a list, a sequence, or a symbol"));
1089 }
1090 for (size_t i=0; i<symbols.nops(); i++) {
1091 if (!symbols.op(i).info(info_flags::symbol)) {
1092 throw(std::invalid_argument("lsolve(): 2nd argument must be a list or a sequence of symbols"));
1093 }
1094 }
1095
1096 // build matrix from equation system
1097 matrix sys(eqns.nops(),symbols.nops());
1098 matrix rhs(eqns.nops(),1);
1099 matrix vars(symbols.nops(),1);
1100
1101 for (size_t r=0; r<eqns.nops(); r++) {
1102 const ex eq = eqns.op(r).op(0)-eqns.op(r).op(1); // lhs-rhs==0
1103 const symbolset syms(eq);
1104 ex linpart = eq;
1105 for (size_t c=0; c<symbols.nops(); c++) {
1106 if (!syms.has(symbols.op(c)))
1107 continue;
1108 const ex co = eq.coeff(ex_to<symbol>(symbols.op(c)),1);
1109 linpart -= co*symbols.op(c);
1110 sys(r,c) = co;
1111 }
1112 linpart = linpart.expand();
1113 rhs(r,0) = -linpart;
1114 }
1115
1116 // test if system is linear and fill vars matrix
1117 const symbolset sys_syms(sys);
1118 const symbolset rhs_syms(rhs);
1119 for (size_t i=0; i<symbols.nops(); i++) {
1120 vars(i,0) = symbols.op(i);
1121 if (sys_syms.has(symbols.op(i)))
1122 throw(std::logic_error("lsolve: system is not linear"));
1123 if (rhs_syms.has(symbols.op(i)))
1124 throw(std::logic_error("lsolve: system is not linear"));
1125 }
1126
1127 matrix solution;
1128 try {
1129 solution = sys.solve(vars,rhs,options);
1130 } catch (const std::runtime_error & e) {
1131 // Probably singular matrix or otherwise overdetermined system:
1132 // It is consistent to return an empty list
1133 return lst{};
1134 }
1135 GINAC_ASSERT(solution.cols()==1);
1136 GINAC_ASSERT(solution.rows()==symbols.nops());
1137
1138 // return list of equations of the form lst{var1==sol1,var2==sol2,...}
1139 lst sollist;
1140 for (size_t i=0; i<symbols.nops(); i++)
1141 sollist.append(symbols.op(i)==solution(i,0));
1142
1143 return sollist;
1144 }
1145
1146 //////////
1147 // Find real root of f(x) numerically
1148 //////////
1149
1150 const numeric
fsolve(const ex & f_in,const symbol & x,const numeric & x1,const numeric & x2)1151 fsolve(const ex& f_in, const symbol& x, const numeric& x1, const numeric& x2)
1152 {
1153 if (!x1.is_real() || !x2.is_real()) {
1154 throw std::runtime_error("fsolve(): interval not bounded by real numbers");
1155 }
1156 if (x1==x2) {
1157 throw std::runtime_error("fsolve(): vanishing interval");
1158 }
1159 // xx[0] == left interval limit, xx[1] == right interval limit.
1160 // fx[0] == f(xx[0]), fx[1] == f(xx[1]).
1161 // We keep the root bracketed: xx[0]<xx[1] and fx[0]*fx[1]<0.
1162 numeric xx[2] = { x1<x2 ? x1 : x2,
1163 x1<x2 ? x2 : x1 };
1164 ex f;
1165 if (is_a<relational>(f_in)) {
1166 f = f_in.lhs()-f_in.rhs();
1167 } else {
1168 f = f_in;
1169 }
1170 const ex fx_[2] = { f.subs(x==xx[0]).evalf(),
1171 f.subs(x==xx[1]).evalf() };
1172 if (!is_a<numeric>(fx_[0]) || !is_a<numeric>(fx_[1])) {
1173 throw std::runtime_error("fsolve(): function does not evaluate numerically");
1174 }
1175 numeric fx[2] = { ex_to<numeric>(fx_[0]),
1176 ex_to<numeric>(fx_[1]) };
1177 if (!fx[0].is_real() || !fx[1].is_real()) {
1178 throw std::runtime_error("fsolve(): function evaluates to complex values at interval boundaries");
1179 }
1180 if (fx[0]*fx[1]>=0) {
1181 throw std::runtime_error("fsolve(): function does not change sign at interval boundaries");
1182 }
1183
1184 // The Newton-Raphson method has quadratic convergence! Simply put, it
1185 // replaces x with x-f(x)/f'(x) at each step. -f/f' is the delta:
1186 const ex ff = normal(-f/f.diff(x));
1187 int side = 0; // Start at left interval limit.
1188 numeric xxprev;
1189 numeric fxprev;
1190 do {
1191 xxprev = xx[side];
1192 fxprev = fx[side];
1193 ex dx_ = ff.subs(x == xx[side]).evalf();
1194 if (!is_a<numeric>(dx_))
1195 throw std::runtime_error("fsolve(): function derivative does not evaluate numerically");
1196 xx[side] += ex_to<numeric>(dx_);
1197 // Now check if Newton-Raphson method shot out of the interval
1198 bool bad_shot = (side == 0 && xx[0] < xxprev) ||
1199 (side == 1 && xx[1] > xxprev) || xx[0] > xx[1];
1200 if (!bad_shot) {
1201 // Compute f(x) only if new x is inside the interval.
1202 // The function might be difficult to compute numerically
1203 // or even ill defined outside the interval. Also it's
1204 // a small optimization.
1205 ex f_x = f.subs(x == xx[side]).evalf();
1206 if (!is_a<numeric>(f_x))
1207 throw std::runtime_error("fsolve(): function does not evaluate numerically");
1208 fx[side] = ex_to<numeric>(f_x);
1209 }
1210 if (bad_shot) {
1211 // Oops, Newton-Raphson method shot out of the interval.
1212 // Restore, and try again with the other side instead!
1213 xx[side] = xxprev;
1214 fx[side] = fxprev;
1215 side = !side;
1216 xxprev = xx[side];
1217 fxprev = fx[side];
1218
1219 ex dx_ = ff.subs(x == xx[side]).evalf();
1220 if (!is_a<numeric>(dx_))
1221 throw std::runtime_error("fsolve(): function derivative does not evaluate numerically [2]");
1222 xx[side] += ex_to<numeric>(dx_);
1223
1224 ex f_x = f.subs(x==xx[side]).evalf();
1225 if (!is_a<numeric>(f_x))
1226 throw std::runtime_error("fsolve(): function does not evaluate numerically [2]");
1227 fx[side] = ex_to<numeric>(f_x);
1228 }
1229 if ((fx[side]<0 && fx[!side]<0) || (fx[side]>0 && fx[!side]>0)) {
1230 // Oops, the root isn't bracketed any more.
1231 // Restore, and perform a bisection!
1232 xx[side] = xxprev;
1233 fx[side] = fxprev;
1234
1235 // Ah, the bisection! Bisections converge linearly. Unfortunately,
1236 // they occur pretty often when Newton-Raphson arrives at an x too
1237 // close to the result on one side of the interval and
1238 // f(x-f(x)/f'(x)) turns out to have the same sign as f(x) due to
1239 // precision errors! Recall that this function does not have a
1240 // precision goal as one of its arguments but instead relies on
1241 // x converging to a fixed point. We speed up the (safe but slow)
1242 // bisection method by mixing in a dash of the (unsafer but faster)
1243 // secant method: Instead of splitting the interval at the
1244 // arithmetic mean (bisection), we split it nearer to the root as
1245 // determined by the secant between the values xx[0] and xx[1].
1246 // Don't set the secant_weight to one because that could disturb
1247 // the convergence in some corner cases!
1248 constexpr double secant_weight = 0.984375; // == 63/64 < 1
1249 numeric xxmid = (1-secant_weight)*0.5*(xx[0]+xx[1])
1250 + secant_weight*(xx[0]+fx[0]*(xx[0]-xx[1])/(fx[1]-fx[0]));
1251 ex fxmid_ = f.subs(x == xxmid).evalf();
1252 if (!is_a<numeric>(fxmid_))
1253 throw std::runtime_error("fsolve(): function does not evaluate numerically [3]");
1254 numeric fxmid = ex_to<numeric>(fxmid_);
1255 if (fxmid.is_zero()) {
1256 // Luck strikes...
1257 return xxmid;
1258 }
1259 if ((fxmid<0 && fx[side]>0) || (fxmid>0 && fx[side]<0)) {
1260 side = !side;
1261 }
1262 xxprev = xx[side];
1263 fxprev = fx[side];
1264 xx[side] = xxmid;
1265 fx[side] = fxmid;
1266 }
1267 } while (xxprev!=xx[side]);
1268 return xxprev;
1269 }
1270
1271
1272 /* Force inclusion of functions from inifcns_gamma and inifcns_zeta
1273 * for static lib (so ginsh will see them). */
1274 unsigned force_include_tgamma = tgamma_SERIAL::serial;
1275 unsigned force_include_zeta1 = zeta1_SERIAL::serial;
1276
1277 } // namespace GiNaC
1278