Add Expression.coefficient(...expand=True) keyword

[rwst]

There is no reason why there should be different results:

sage: (x*(x*y+y^2)).coefficient(x)
y
sage: (x*(x*y+y^2)).coefficient(x,2)
0
sage: (x*(x*y+y^2)).expand().coefficient(x)
y^2
sage: (x*(x*y+y^2)).expand().coefficient(x,2)
y

This would also be unsurprising for Mma users, see #9505 comment:6

Maybe add keyword expand=True.

Component: symbolics

Author: Ralf Stephan

Branch/Commit: u/rws/20824 @ 7ab049f

Issue created by migration from https://trac.sagemath.org/ticket/20824

[rwst]

Branch: u/rws/expression_coefficient___problems

[rwst]

Author: Ralf Stephan

[rwst]

Commit: a45909c

[rwst]

New commits:

a45909c

20824: add Expression.coefficient(...expand=True) keyword

[mezzarobba]

comment:6

Hmm, I don't really see the benefit compared to expr.expand().coefficient(...)...

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

1d6fc68

Merge branch 'develop' into t/20824/expression_coefficient___problems

[sagetrac-git]

Changed commit from a45909c to 1d6fc68

[rwst]

Changed branch from u/rws/expression_coefficient___problems to u/rws/20824

[rwst]

New commits:

7ab049f

20824 Add Expression.coefficient(...expand=True) keyword

[rwst]

Changed commit from 1d6fc68 to 7ab049f

[bryangingechen]

comment:10

I had a look at the patch:

• It looks like r is assigned in the try block but then not returned or called afterwards. Is this necessary? (I haven't completely digested the pynac interface so I may be missing something, but this looks strange...)
• Should this be added to coefficients as well?
• The indentation to TESTS: in the docstring was changed accidentally.

[mkoeppe]

Branch has merge conflicts