On Fri, May 30, 2014 at 12:17 AM, William Stein <[email protected]> wrote:
> On Thu, May 29, 2014 at 11:37 AM, Simon King <[email protected]> > wrote: > > Hi Stephen > > > > On 2014-05-29, Stephen Kauffman <[email protected]> wrote: > >> Specifically I have a polynomial such as mypoly = X*Y + 1 in > >> BooleanPoynomialRing() and str(mypoly) converts it to the string 'X*Y + > 1' > >> then I do some stuff with re pattern matching to construct the string > '1 - > >> x*y' which I now want to convert to a polynomial in 'x' and 'y' in QQ. > Are > >> there any built in functions or methods to do that? > > > > Generally, if you have an algebraic structure Y (often called "parent") > in > > Sage, and have some element x of some other algebraic structure x, then > > Y(x) tries to convert x into an element of Y. The same holds for > > conversion of a string. > > > > Note, however, that a conversion is not necessarily making mathematical > > sense, if the structures X and Y are too different (i.e., there may be > > no homomorphism from X to Y). So, use conversions only if you know what > > you are doing. > > > > What you describe would be as follows: > > sage: P.<x,y> = BooleanPolynomialRing() > > sage: mypoly = x*y+1 > > sage: R = QQ['x','y'] > > sage: R(mypoly) > > x*y + 1 > > sage: R('1-x*y') # replacing + by - in str(mypoly) > > x*y - 1 > > > > Best regards, > > Simon > > Simon -- great answer -- like my second one but even better. This > seems like the sort of thing our FAQ should have. Believe it or not, > we have a Sage FAQ: > > http://sagemath.org/doc/faq/ > > I doubt it has been touched in years, and I doubt anybody even knows > how to change it... > > And, this one still mentions Mercurial for the development among other things!!! I have opened a ticket to change this (now, I will have to figure how to do that but still...): http://trac.sagemath.org/ticket/16412 -- Kannappan. > > > > > > -- > > You received this message because you are subscribed to the Google > Groups "sage-support" group. > > To unsubscribe from this group and stop receiving emails from it, send > an email to [email protected]. > > To post to this group, send email to [email protected]. > > Visit this group at http://groups.google.com/group/sage-support. > > For more options, visit https://groups.google.com/d/optout. > > > > -- > William Stein > Professor of Mathematics > University of Washington > http://wstein.org > > -- > You received this message because you are subscribed to the Google Groups > "sage-support" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/sage-support. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
