On Thu, May 29, 2014 at 11:37 AM, Simon King <simon.k...@uni-jena.de> wrote:
> Hi Stephen
>
> On 2014-05-29, Stephen Kauffman <strangerl...@gmail.com> 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...
>
>
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William Stein
Professor of Mathematics
University of Washington
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