March 2002 - PURRS-devel - BUGSENG Mailman

purrs/tests recurrences
by Alessandro Zaccagnini 13 Mar '02

13 Mar '02

CVSROOT: /cvs/purrs Module name: purrs Changes by: zaccagnini(a)cs.unipr.it 2002-03-13 19:31:12 Modified files: tests : recurrences Log message: A few more test recurrences. Patches: http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/purrs/tests/recurrences.diff?cvsr…

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purrs/doc purrs.tex
by Alessandro Zaccagnini 13 Mar '02

13 Mar '02

CVSROOT: /cvs/purrs Module name: purrs Changes by: zaccagnini(a)cs.unipr.it 2002-03-13 14:48:45 Modified files: doc : purrs.tex Log message: 1. Eliminated/modified some obsolete comments from Section 3.1; 2. Added remarks on the roots of the characteristic equation in section 2.1.1, and expanded the same section to contain explanations using the language of linear algebra; in particular, introduced a suitable class of specially "summable" sequences; 3. Expanded section on systems of linear recurrences and added appropriate references; 4. Added preliminary comment on prerequisites in section 1; 5. Added section on the reduction of the order. Patches: http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/purrs/doc/purrs.tex.diff?cvsroot=…

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purrs/tests recurrences
by Alessandro Zaccagnini 13 Mar '02

13 Mar '02

CVSROOT: /cvs/purrs Module name: purrs Changes by: zaccagnini(a)cs.unipr.it 2002-03-13 09:27:43 Modified files: tests : recurrences Log message: Added a few more recurrences. Patches: http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/purrs/tests/recurrences.diff?cvsr…

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purrs/tests recurrences
by Alessandro Zaccagnini 12 Mar '02

12 Mar '02

CVSROOT: /cvs/purrs Module name: purrs Changes by: zaccagnini(a)cs.unipr.it 2002-03-12 18:53:52 Added files: tests : recurrences Log message: Some test recurrences taken from various sources. Patches: http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/purrs/tests/recurrences.diff?cvsr…

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Behavior of the function 'has'
by Tatiana Zolo 12 Mar '02

12 Mar '02

I do not understand the behavior of the function 'has' in some case. I show you the problem with ginsh: > has(2^x*3^x, $0^x); 1 > has(2^x*3^x*4^x, $0^x); 1 > has(2^x*3^x, $0^x*$1^x); 1 > has(2^x*3^x*4^x, $0^x*$1^x); 0 > has(2^x*3^x*4^x, $0^x*$1^x*$2^x); 1 I would expect that also has(2^x*3^x*4^x, $0^x*$1^x); answers 'true' because I see $0^x*$1^x as a subexpression of 2^x*3^x*4^x. Same thing without to use wildcard. > has(2^x*3^x*4^x, 2^x); 1 > has(2^x*3^x*4^x, 2^x*3^x); 0 > has(2^x*3^x*4^x, 2^x*3^x*4^x); 1 Regards Tatiana Zolo

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purrs/tests rrs_driver.cc
by Roberto Bagnara 09 Mar '02

09 Mar '02

CVSROOT: /cvs/purrs Module name: purrs Changes by: roberto(a)cs.unipr.it 2002-03-09 17:12:41 Modified files: tests : rrs_driver.cc Log message: Print the solution, when NOISY. Patches: http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/purrs/tests/rrs_driver.cc.diff?cv…

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w3purrs/htdocs purrs.raw
by Roberto Bagnara 09 Mar '02

09 Mar '02

CVSROOT: /cvs/purrs Module name: w3purrs Changes by: roberto(a)cs.unipr.it 2002-03-09 16:44:14 Modified files: htdocs : purrs.raw Log message: Invoke the recurrence equations demo. Patches: http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/w3purrs/htdocs/purrs.raw.diff?cvs…

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purrs demos/Makefile.am demos/purrs_rrs_cgi.cc ...
by Roberto Bagnara 09 Mar '02

09 Mar '02

CVSROOT: /cvs/purrs Module name: purrs Changes by: roberto(a)cs.unipr.it 2002-03-09 16:43:49 Modified files: demos : Makefile.am purrs_rrs_cgi.cc src : rr_solver.cc rr_solver.hh tests : rrs_driver.cc Log message: Now solve() takes a `solution' argument to store the result, if any. First rough cut at a recurrence equation demo. Patches: http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/purrs/demos/Makefile.am.diff?cvsr… http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/purrs/demos/purrs_rrs_cgi.cc.diff… 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… http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/purrs/tests/rrs_driver.cc.diff?cv…

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

08 Mar '02

CVSROOT: /cvs/purrs Module name: purrs Changes by: zolo(a)cs.unipr.it 2002-03-08 10:00:54 Modified files: src : rr_solver.cc Log message: Fixed the case in which the user inserts only a function in n or a constant. Patches: http://www.cs.unipr.it/cgi-bin/cvsweb.cgi/purrs/src/rr_solver.cc.diff?cvsro…

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Re: What is a polynomial in x?
by Roberto Bagnara 07 Mar '02

07 Mar '02

Christian Bauer wrote: >>2) It is legal to say degree(sqrt(2)*x). >> > > Yes. > > >>But then it would be useful to precisely characterize the class of >>expressions e and x such that degree(e, x) is well defined. >> > > Is this possible? There might be terms sqrt(x) in e that cancel each other > after some transformations, so while the input expression might logically > be a polynomial, it is syntactically not. I perfectly agree. In fact, what we are looking for is a _syntactic_ characterization of those GiNaC expressions for which degree, ldegree, coeff, tcoeff and lcoeff are guaranteed to give the right result. > 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. This is one possible syntactic characterization. Is this the one that the authors of GiNaC would like to adopt as _the_ definition of the syntactic domain where degree() and friends return a sensible result? Moreover, when degree() is called on something outside this domain, wouldn't it be better to throw an exception instead of returning with a value obtained in an undocumented way? Providing a function checking whether a given expression is inside the syntactic domain would also be useful (yes, we have been bitten by this kind of problem ;-) What do you think? Roberto -- 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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