Interface to Groebner Fan

AUTHOR:

• Anders Nedergaard Jensen: Write gfan C++ program, which implements algorithms many of which were invented by Jensen, Komei Fukuda, and Rekha Thomas.
• William Stein (2006-03-18): wrote gfan interface (first version)
• Marshall Hampton (2008-03-17): modified to use gfan-0.3, subprocess instead of os.popen2

TODO – much functionality of gfan-0.3 is still not exposed:

* at most 52 variables:

    - use gfan_substitute to make easier (?)
    MH: I think this is now irrelevant since gfan can accept the original ring variables

* --symmetry is really useful
         - permutations are 0-based *not* cycle notation; a <---> 0
  output is broken up much more nicely.

* -- can work in Z/pZ for p <= 32749

* -- can compute individual GB's for lex and revlex (via buchberger)

class sage.interfaces.gfan.Gfan

Interface to Anders Jensen’s Groebner Fan program.