On 03/28/2012 06:14 PM, Mark Shimozono wrote:
Suppose I want to create a custom subclass of a polynomial ring.
From which class should it inherit? It should not care so much about
the
eventual base ring.
I'm a sage development newbie.
Where can I read about the class hierarchy for sage polynomials?
I'm a little confused at the organizational principle behind the
following output.
I can answer half of your question: the documentation is either in the
reference manual,
http://sagemath.org/doc/reference/polynomial_rings.html
or the source code:
sage: R = PolynomialRing(QQ,['x'])
sage: R?
At the top, you'll see something like,
Source File: /home/mjo/src/sage-5.0.beta9/devel/sage/sage/rings
/polynomial/polynomial_ring.py
Which should give you a hint where to look. In this case, I think you
would find your way to,
sage/rings/polynomial/polynomial_ring_constructor.py
where the real magic happens.
sage: R = PolynomialRing(QQ,['x'])
sage: R.__class__
<class
'sage.rings.polynomial.polynomial_ring.PolynomialRing_field_with_category'>
sage: R.an_element().__class__
<type
'sage.rings.polynomial.polynomial_rational_flint.Polynomial_rational_flint'>
Sage uses different libraries for different types of polynomials. It
looks like we use flint for univariate over the rationals. If you
construct it over the reals, you get something else.
sage: S = PolynomialRing(QQ,['x','y'])
sage: S.__class__
<type
'sage.rings.polynomial.multi_polynomial_libsingular.MPolynomialRing_libsingular'>
sage: S.an_element().__class__
<type
'sage.rings.polynomial.multi_polynomial_libsingular.MPolynomial_libsingular'>
Multivariate polynomials over the rationals are implemented in
libsingular instead, so they use a different class than in the
univariate case.
The choice of which to use is made in the PolynomialRing() constructor,
which hands off the work to either the _single_variate() or
_multi_variate() functions accordingly.
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