some small polybori interface fixes

[malb]

• implement var()
• implemented new functions required by PolyBoRi?
• fixed a few things in MPolynomialSystem

[mhansen]

Why does variables() return an iterator? It returns a tuple for pretty much everything else in Sage. See #7077

[malb]

Because that's what PolyBoRi? expects internally.

[mhansen]

Can you explain in a bit more detail? How is PolyBoRi? using that method?

[malb]

Hi Mike, sorry for being so brief earlier, I was in a rush.

PolyBoRi? calls this function from various functions which are called by the groebner_basis function. The ones I could find quickly are:

polybori-0.6/pyroot/polybori/rank.py:    return p.lex_lead().variables().next()
polybori-0.6/pyroot/polybori/ll.py:      return Monomial(v).variables().next().index()
polybori-0.6/testsuite/py/parsegat.py:    return p.lead().variables().next()

As you can see, it calls next() immediatly on the result of variables(). Right now, certain GB computations will fail with an AttributeError because of this.

[malb]

I just received word that this will be changed in PolyBoRi?.

[PolyBoRi]

​http://bitbucket.org/brickenstein/polybori/changeset/48fab65072e9/

​http://bitbucket.org/brickenstein/polybori/changeset/e238ae62b9e6/

Regarding parsegat, as you can see, I moved a corrected version between our repositories (similar one-liner). But there is no dependency on parsegat.py . The only funny thing about the recent versions of parsegat.py is that, you can see a poor mathetician trying to recognize patterns from bad encoded circuits. I still have nightmares from it.

[malb]

I prepared a new SPKG and a new patch.

The SPKG is available at:

​http://sage.math.washington.edu/home/malb/spkgs/polybori-0.6.3.r1647-20091028.spkg

[malb]

Mike, I reversed the iterator change in the latest patch. Can you review it?

[malb]

I am attaching a new deps file to this ticket, to address

​http://groups.google.com/group/sage-devel/browse_thread/thread/122f067d8947148d/

[malb]

The only thing changed in the deps file (which isn't under revision control) is that PolyBoRi? now depends on M4RI

[drkirkby]

There are several issues I am aware of with m4ri, which should perhaps be sorted out before code is added that depends on it.

#7171 - Although reported against HP-UX, this is more serious, as it is broken on Solaris too. #7037 - libm4ri thinks the C compiler is broken

I beleive the current version of PolyBoRi? might actually build with Sun's compiler, but this would stop that, if it has a dependancy which does not.

[drkirkby]

Oops, for some reason I was not aware of this ticket despite being CCed on it. Nor of #7375, which aims to address the issues in M4RI, so my comments are probably out of place. I will look at #7375 soon, but would be unable to review this ticket.

Dave

[malb]

Hi, I was wondering if I someone could review this ticket now that the M4RI issues are resolved?

[mhansen]

The patch looks good. I'll add it first thing after 4.3, which should hopefully be out in the next day or two.