La recherche a retourné 331 résultats

par lukamar
sam. juil. 13, 2019 11:46 am
Forum : Bugs
Sujet : testing validity of an inequality misses a special case
Réponses : 1
Vues : 1651

testing validity of an inequality misses a special case

Hello,

when one sets

Code : Tout sélectionner

assume(t>-1 and t<1)
then the command

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abs(t)>0
returns "true". However, abs(t)=0 for t=0.
par lukamar
lun. juil. 08, 2019 8:20 pm
Forum : Giac
Sujet : Gamma(n) = (n-1)!
Réponses : 3
Vues : 2654

Re: Gamma(n) = (n-1)!

Thanks for the code, it's really a simple solution, but I do not know about possible side effects either. Perhaps it's better to leave the simplification to individual commands than doing it automatically.
par lukamar
lun. juil. 08, 2019 10:47 am
Forum : Giac
Sujet : Gamma(n) = (n-1)!
Réponses : 3
Vues : 2654

Gamma(n) = (n-1)!

Hello, Giac does some simplifications of sin(n*pi) and cos(n*pi) after assume(n,integer). I propose a similar simplification for the gamma function, i.e. that Gamma(n) returns (n-1)! when n is a symbol assumed to be a positive integer. Something similar could also be done with the Beta function, as ...
par lukamar
jeu. juin 20, 2019 4:27 pm
Forum : Xcas - English
Sujet : A problem formatting a list returned from solve()
Réponses : 4
Vues : 2364

Re: A problem formatting a list returned from solve()

Maybe the output would be more readable if the subtype of the result from solve was changed to _LIST__VECT?
That would, however, disable stacking the solutions one above another...
par lukamar
jeu. juin 20, 2019 4:17 pm
Forum : Giac
Sujet : domain and about
Réponses : 2
Vues : 2445

Re: domain and about

Indeed! Thanks!
par lukamar
mar. juin 18, 2019 8:35 pm
Forum : Giac
Sujet : domain and about
Réponses : 2
Vues : 2445

domain and about

Hello, I think that 'domain' command should intersect its result with the set obtained by 'about' command (the real case). For example, when entering assume(x<1); domain(ln(x),x) one obtains x>0, but shouldn't it be x>0 and x<1? Also, by doing the intersection domain(x) would return x<1, i.e. the do...
par lukamar
dim. mai 12, 2019 5:44 pm
Forum : Giac
Sujet : defininig periodic functions
Réponses : 4
Vues : 4904

Re: defininig periodic functions

Hello Bernard, I noticed a bug in periodic command. On the line 6195 in intg.cc there is a check if (e.type!=_SYMB) return gentypeerr(contextptr); It should be removed (i.e. lines 6195-6196 deleted) because it prevents entering e.g. x as the first argument. By the way, I also coded a better implemen...
par lukamar
ven. mars 08, 2019 2:42 pm
Forum : Giac
Sujet : graph theory commands for Giac
Réponses : 198
Vues : 62311

Re: graph theory commands for Giac

New updates: * traveling_salesman now works with digraphs too, I also improved the code for undirected graphs, * hamiltonicity testing for digraphs is improved, * imported graphs are now checked for duplicate vertex labels, * graph theory manual is updated and I corrected/added some examples in aide...
par lukamar
jeu. févr. 28, 2019 10:21 am
Forum : Giac
Sujet : graph theory commands for Giac
Réponses : 198
Vues : 62311

Re: graph theory commands for Giac

Hi, I have improved is_hamiltonian command, now it uses a backtracking algorithm and works with digraphs as well as with undirected graphs. It does not call traveling_salesman anymore. The backtracking technique is simple but it works well on smaller graphs. I changed the corresponding entry in the ...
par lukamar
mar. févr. 26, 2019 5:15 pm
Forum : Giac
Sujet : nonlinear optimization functions
Réponses : 77
Vues : 46605

Re: nonlinear optimization functions

Thanks! Do you perhaps have deb files compiled with nauty and GLPK? Btw, I fixed couple of bugs in optimization.cc today. The command extrema has been having some problems with critical point classification which produced incorrect or not well defined results in some cases. Also, minimax was crashin...
par lukamar
ven. févr. 22, 2019 8:55 am
Forum : Giac
Sujet : nonlinear optimization functions
Réponses : 77
Vues : 46605

Re: nonlinear optimization functions

Can't reproduce the crash with extrema(x*y*z,x^2+y^2+z^2=1,[x,y,z]) on ubuntu in 1.5.0-43. It's working fine now. By the way, there is incompatibility between giac and ubuntu 18.04, I had to install couple of deb packages by hand (libreadline6, for example). That was on a clean ubuntu install with g...
par lukamar
lun. févr. 18, 2019 11:12 am
Forum : Xcas - English
Sujet : some problem with determinant of a matrix
Réponses : 4
Vues : 2106

Re: some problem with determinant of a matrix

Hello Jose,
I think that mixing approx values with symbols is the problem here, but Bernard will know better. As a workaround, I propose applying "exact" before computing the determinant:

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det(exact(m))
Luka
par lukamar
ven. févr. 15, 2019 7:34 pm
Forum : Giac
Sujet : graph theory commands for Giac
Réponses : 198
Vues : 62311

Re: graph theory commands for Giac

I made another small fix, this time in graphe::adjacent_nodes (duplicate vertex entries were produced). graphtheory.cc is also updated.
par lukamar
ven. févr. 15, 2019 6:09 pm
Forum : Giac
Sujet : graph theory commands for Giac
Réponses : 198
Vues : 62311

Re: graph theory commands for Giac

There should be changes at lines 1148, 1176 and 1180 in graphtheory.cc. I pushed another commit today fixing a small bug in graphe.cc (line 2260 is inserted). I see those changes in my github repository. Try pulling it again, maybe it will work this time.
par lukamar
jeu. févr. 14, 2019 2:28 pm
Forum : Giac
Sujet : graph theory commands for Giac
Réponses : 198
Vues : 62311

Re: graph theory commands for Giac

Hi,
I have committed a small fix for has_arc command. It hasn't been accepting vertex types other than integer.