Le forum de XCAS

Indeed I should have add a hash method but I don't know a hash function for a gen in giac. Bernard, is there already some hash function in giac that I could use because I fear that: def __hash__(self): return hash(str(self)) would help but it could be very slow. I think using str is a bad idea e.g....

Hi, Maybe this is a giacpy tip of the day, or maybe this is a question... In python it would sometimes be beneficial if you could put some giacpy gen types into a dictionary or a set. As a simple example, consider a polynomial x^2+1. The following code will fail from giacpy import giac f=giac("x^2+1...

Hi, is there no way to use the command factors to get (a list of) the complex linear factors of a real univariate polynomial? I want something like "factors" but for complex factors. There is cFactor but the return does not seem to be a list but an expression (can we make it return me a list?). Ther...

Well, I really did not want to use Gröbner basis for this. But thanks for the suggestion.

Jose

Hi, In maple there is a function called "algsubs" which allows me to use an expression (usually algebraic) on a given expression. For instance algsubs(l2^2=1,l2^2+l2^3) will yield "l2+1" Is there a similar thing in XCas/giac (without going into complex method like grobner basis). For easy conditions...

Hi, Here is a python script that baffles me a bit. from giacpy import giac Tv2= giac("matrix[[(-2*l1*l2+2)/2,(2*l1+2*l2)/2,0,0,(-l1*a2-l1*a1-l2*a2-l2*a1)/2,(-l1*l2*a2-l1*l2*a1+a2+a1)/2,(-l1*d2+l2*d2)/2,(l1*l2*d2+d2)/2,0,0,0,0,0,0,0,0],[0,0,(-2*l1+2*l2)/2,(2*l1*l2+2)/2,(l1*l2*d2-d2)/2,(-l1*d2-l2*d2)/...

Thanks Bernard. Yes you are right. I guess though, kernel computation should still be done manually? The reason is because even after gauss jordan without division there are multiplications involved, and there is a problem if the multiplication is done symbolically because there will be specific cas...

Hi,

Is there an option (e.g. in rref or ref) where I can row reduce a matrix without diivsion? I do sometimes have matrices with symbolic entries and division are not allowed in this case. This is especially important for me when computing the kernel of a matrix with some symbolic entries.

Jose

Thank you Bernard. Yes, I suspected that this can be easily added if it was not there (otherwise, I usually do not want to request features). I think it is ok however way you want to add this option (I will adapt myself to it). Your suggestion is also very good.

There is the possibility of orthogonalizing without taking roots in gramschmidt (which is in effect the same code but you do not normalize). This seems to be available in giac C++ code but I do not know how to use it (or if it is available) in XCas or giacpy. For instance in giacpy we get the typica...

Thank you Frederic. This is very good news for me. Bernard says that in effect Gröbner basis computation will not be affected if Pari is linked with giac (without linking to ntl), but I suspect this is still improved. I will report if I notice any signifcant change also with gbasis computations. Edi...

Can you replicate this as a gbasis command? You mean in Xcas or giacpy? I can only replicated this in visual studio with _gbasis (gbasis command for C++). I feel that the vector is not recognized here and so the conversion is not taking place. It will be a very long debug before I can figure out wh...

Is the heart of the groebner basis computation in solve.cc or cocoa.cc? For some reasone the Visual Studio build goes to through the cocoa.cc code and attempts to call convert (line ca. 12295). The reason why I know this is because I get the text "not found" in the console which comes from this line...

Oh that's a pity. I thought, for linux, installation from python wheel would get me all the dependencies (including possibly sources). This would allow easier installation for non-programmer users. I did a little talk in the university to a group of colleagues promoting both giac and giacpy but I co...

Hi Frederic, I was wondering if you can install giacpy wheel using pip installer in Debian systems? Sorry if I do not follow the linux development very closely. I tried doing so and I got complaints on compiling: Command /usr/bin/python -c "import setuptools, tokenize;__file__='/tmp/pip-build-Tj_9pE...