sympy/sympy — pull request #1218 by ness01 (2012-04-06 15:28:39+00:00)
Title: AGCA 4: ideals, syzygies, and expression in terms of generators

The fourth installment in my series of pull requests. I had hoped to do quotient rings today, but this PR has already reached my 800 lines target again. New in this PR:

- an abstract class for ideals, and a concrete implementation using free modules of rank one and their submodules
- computing syzygies of submodules
- expressing elements of a submodule or ideal in terms of generators

Please review!