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| loose of sign when using imap for mapping polynomials from o https://www.singular.uni-kl.de/forum/viewtopic.php?f=10&t=1769 |
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| Author: | madalina [ Fri Aug 28, 2009 11:24 am ] |
| Post subject: | loose of sign when using imap for mapping polynomials from o |
I want to map some polynomials from the ring of reals to the ring of rationals, using imap. Thus when using imap (or fetch), the sign of the polynomials in the new ring are not preserved, I always obtain only positive coefficients. Here is the code example: > ring r=real, (x,y), dp; > poly f= -1+2x2+3y3-2x-3y; > poly g= -1-2x2-3y3+x+3y; > ideal m=f,g; > ring t=0,(x,y),dp; > ideal n=imap(r,m); > n[1]; 3y3+2x2+2x+3y+1 > n[2]; 3y3+2x2+x+3y+1 > poly newf=imap(r,f); > poly newg=imap(r,g); > newf; 3y3+2x2+2x+3y+1 > newg; 3y3+2x2+x+3y+1 I would really appreciate if someone could give me some hints on how to preserve the sign of the original coefficients in the new ring (and if someone can explain me what happens). thanks you in advance, madalina |
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| Author: | Ravi [ Sat Aug 29, 2009 8:06 am ] |
| Post subject: | Re: loose of sign when using imap for mapping polynomials from o |
If you specify the number of decimal places while defining the ring, then there is no problem: ring r=(real,10), (x,y), dp; I do not know why the problem occurs, but this works. See Section 3.3.1 of the Singular manual for the syntax. |
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| Author: | Guest [ Mon Aug 31, 2009 11:54 am ] |
| Post subject: | Re: loose of sign when using imap for mapping polynomials from o |
thank you, the conversion is working now, madalina |
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