October 2002 - PURRS-devel - BUGSENG Mailman

purrs/src rr_solver.cc
by Alessandro Zaccagnini 09 Oct '02

09 Oct '02

CVSROOT: /cvs/purrs Module name: purrs Changes by: zaccagnini(a)cs.unipr.it 2002-10-09 18:39:50 Modified files: src : rr_solver.cc Log message: Fixed the first few comments. Patches: http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/purrs/src/rr_solver.cc.diff?cvsro…

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purrs/src Recurrence.defs.hh
by Roberto Bagnara 09 Oct '02

09 Oct '02

CVSROOT: /cvs/purrs Module name: purrs Changes by: roberto(a)cs.unipr.it 2002-10-09 18:33:56 Modified files: src : Recurrence.defs.hh Log message: A little step forward. Patches: http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/purrs/src/Recurrence.defs.hh.diff…

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Now seriously: what is a polynomial?
by Roberto Bagnara 09 Oct '02

09 Oct '02

Dear all, this message is a first of a small series where we try to summarize our difficulties with GiNaC and its (lack of) documentation. As a general remark, several concepts are defined only through examples whereas formal definitions would help greatly. In this message we concentrate on one concept that is central to our application: the concept of "polynomial". Here are our sources of information: 1) The tutorial: a bunch of examples are presented that, however do not clarify the general idea. 2) The method `info(info_flags::polynomial)' should constitute, we used to believe, the very formal specification of the notion of "being a polynomial". 3) The message by Christian Bauer (March 7th, 2002, see http://www.ginac.de/lists/ginac-list/msg00232.html): "But this is the intended behavior: If e is of the form e = sum(i=n1..n2, a_i * x^i) with n1, n2 integer and expressions a_i that satisfy has(a_i, x) == false, then degree(e, x) and ldegree(e, x) are well defined and accurate. I think this should even cover cases like degree(sin(y)^3-sin(y),sin(y)) which is guaranteed to return 3." The problem is that, while 1 is inconclusive, 2 and 3 (with the correction replacing "integer" by "nonnegative integer") conflict with each other. Let us consider the expression e = sqrt(2)*x. Since, clearly, has(sqrt(2), x) == false, `e' is a polynomial for 3. But, since e.info(info_flags::polynomial) == false, `e' is not a polynomial according to 2. The point here is to decide _exactly_ for which class of expressions are the functions degree(), ldegree(), coeff(), lcoeff(), tcoeff(), expand(), collect(), quo(), rem(), prem(), gcd(), lcm(), sqrfree() and so forth guaranteed to work. All the best Roberto Bagnara Alessandro Zaccagnini Enea Zaffanella Tatiana Zolo /***************************************************************************/ #include <ginac/ginac.h> #include <iostream> using namespace GiNaC; using namespace std; int main() { symbol x("x"); ex coeff = sqrt(ex(2)); ex e = coeff*x; cout << (e.info(info_flags::polynomial) ? "true" : "false") << endl; cout << (!has(coeff, x) ? "true" : "false") << endl; return 0; } /***************************************************************************/ -- Prof. Roberto Bagnara Computer Science Group Department of Mathematics, University of Parma, Italy http://www.cs.unipr.it/~bagnara/ mailto:bagnara@cs.unipr.it

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purrs TODO.tex
by Tatiana Zolo 09 Oct '02

09 Oct '02

CVSROOT: /cvs/purrs Module name: purrs Changes by: zolo(a)cs.unipr.it 2002-10-09 11:52:23 Modified files: . : TODO.tex Log message: Added a problem about Gosper's algorithm, in particular about the compute of the resultant's roots. Patches: http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/purrs/TODO.tex.diff?cvsroot=purrs…

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purrs/src rr_solver.cc
by Tatiana Zolo 09 Oct '02

09 Oct '02

CVSROOT: /cvs/purrs Module name: purrs Changes by: zolo(a)cs.unipr.it 2002-10-09 10:25:14 Modified files: src : rr_solver.cc Log message: Implemented `eliminate_null_decrements()' and improved `eliminate_negative_decrements()'. Patches: http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/purrs/src/rr_solver.cc.diff?cvsro…

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purrs/src rr_solver.cc
by Tatiana Zolo 08 Oct '02

08 Oct '02

CVSROOT: /cvs/purrs Module name: purrs Changes by: zolo(a)cs.unipr.it 2002-10-08 15:15:28 Modified files: src : rr_solver.cc Log message: Modified `get_constant_decrement()': now returns also a null decrement. `eliminate_negative_decrements()' not returns a bool: it never fails. Patches: http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/purrs/src/rr_solver.cc.diff?cvsro…

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purrs/src rr_solver.cc rr_solver.hh
by Tatiana Zolo 08 Oct '02

08 Oct '02

CVSROOT: /cvs/purrs Module name: purrs Changes by: zolo(a)cs.unipr.it 2002-10-08 12:03:18 Modified files: src : rr_solver.cc rr_solver.hh Log message: Implemented function `eliminate_negative_decrements()'. Added the enumerate `NOT_LINEAR_RECURRENCE' and catched these cases. Patches: http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/purrs/src/rr_solver.cc.diff?cvsro… http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/purrs/src/rr_solver.hh.diff?cvsro…

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purrs/src simplify.cc
by Tatiana Zolo 08 Oct '02

08 Oct '02

CVSROOT: /cvs/purrs Module name: purrs Changes by: zolo(a)cs.unipr.it 2002-10-08 10:04:36 Modified files: src : simplify.cc Log message: Restored an object Expr (instead of a Number) in order to avoid the rounding of the number. Patches: http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/purrs/src/simplify.cc.diff?cvsroo…

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purrs/src alg_eq_solver.cc gosper.cc poly_fact ...
by Tatiana Zolo 07 Oct '02

07 Oct '02

CVSROOT: /cvs/purrs Module name: purrs Changes by: zolo(a)cs.unipr.it 2002-10-07 16:32:30 Modified files: src : alg_eq_solver.cc gosper.cc poly_factor.cc simplify.cc util.cc Log message: Removed useless assertions before to call `ex_to_number()' (useless because the assertion is contained in the method `ex_to_number()'). Patches: http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/purrs/src/alg_eq_solver.cc.diff?c… http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/purrs/src/gosper.cc.diff?cvsroot=… http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/purrs/src/poly_factor.cc.diff?cvs… http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/purrs/src/simplify.cc.diff?cvsroo… http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/purrs/src/util.cc.diff?cvsroot=pu…

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purrs/src Expr_List.defs.hh
by Tatiana Zolo 07 Oct '02

07 Oct '02

CVSROOT: /cvs/purrs Module name: purrs Changes by: zolo(a)cs.unipr.it 2002-10-07 16:08:47 Modified files: src : Expr_List.defs.hh Log message: Added comments. Patches: http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/purrs/src/Expr_List.defs.hh.diff?…

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