On Thu, May 29, 2014 at 11:22 AM, Stephen Kauffman
<strangerl...@gmail.com> wrote:
> That's a lot simpler than I thought it would be. Thanks. I'm converting free 
> boolean algebra statements to corresponding probability statements with a 
> recursive function hopefully.
>

Yep, there's a general Sage convert functionality, which is often
R(foo), where R is a parent object, and foo is anything that might
make sense.  Be careful though, since it can easily lead to
mathematically meaningless results, since "R(foo)" in Sage means "make
something in R from foo by hook or crook".

Another useful command is sage_eval, which is like Python's eval, but
with the preparser:

R.<x,y> = PolynomialRing(QQ)
sage_eval('1 - x*y', globals())
-x*y + 1

Note that I expect this to work, but it doesn't:

R.<x,y> = PolynomialRing(QQ)
sage_eval('1 - x*y', {x:x, y:y})

> On 5/29/2014 2:17 PM, William Stein wrote:
>> On Thu, May 29, 2014 at 11:13 AM, 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? Or does a python routine
>>> have to be written to accomplish my task? Thanks
>>
>> R.<x,y> = PolynomialRing(QQ)
>> f = R('1 - x*y')
>> f
>>
>>>
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>>
>>
>
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-- 
William Stein
Professor of Mathematics
University of Washington
http://wstein.org

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