Magma interface cannot convert multivariate polynomials back to Sage

[nbruin]

Evidently:

sage: R.<x,y,z>=QQ[]
sage: f=x^2+3*y
sage: magma(f).sage()
NameError: name 'x' is not defined

---

Apply attachment: trac_11580-magma.patch to the extcode repository.

Apply attachment: trac_11580-doctests.patch to the Sage library.

Depends on #11456

Component: interfaces

Author: Nils Bruin

Reviewer: William Stein, Marco Streng

Merged: sage-4.7.2.alpha3

Issue created by migration from https://trac.sagemath.org/ticket/11580

[nbruin]

Author: Nils Bruin

[nbruin]

Attachment: trac_11580-magma_mpols.patch.gz

[nbruin]

comment:2

Updated patch so that magma tuples of length 1 become python tuples (doesn't affect the polynomial bit of the patch)

[williamstein]

comment:3

Hi Nils,

Can you add

sage: R.<x,y,z>=QQ[]
sage: f=x^2+3*y
sage: magma(f).sage()        # optional - magma
x^2 + 3*y  # or whatever

as a doctest in interfaces/magma.py or somewhere?

[nbruin]

Attachment: trac_11580-doctest.patch.gz

[nbruin]

comment:4

Thanks William! Done.

[jdemeyer]

Reviewer: William Stein

[jdemeyer]

Work Issues: Coordinate with #11456

[mstreng]

Changed reviewer from William Stein to William Stein, Marco Streng

[mstreng]

Changed work issues from Coordinate with #11456 to rebase on top of #11456

[mstreng]

comment:9

This patch breaks conversion of finite field elements from Magma to Sage.

Without patch:

sage: magma(GF(2)(1)).sage()
1

With patch:

sage: magma(GF(2)(1)).sage()
...
Segmentation fault
...
Magma crashed executing _sage_[3], _sage_[4] := Sage(_sage_[2]);

With patch:

sage -t -only-optional=magma devel/sage/sage/rings/finite_rings/element_givaro.pyx
(same crash)

When converting finite field elements from Magma to Sage, they are first converted to a SeqEnum of finite field elments. In particular, a proper implementation of conversions of SeqEnum to Sage sets of an infinite loop. This was fixed in #11456, so we should rebase this patch on top of #11456.

[mstreng]

Attachment: trac_11580-doctests.patch.gz

[mstreng]

Changed work issues from rebase on top of #11456 to none

[mstreng]

comment:10

Attachment: trac_11580-magma.patch.gz

Rebased on top of #11456.

Removed the function "intrinsic Sage(X::SeqEnum) -> MonStgElt, BoolElt", because it was equal (modulo documentation) to the one in #11456.

[jdemeyer]

Dependencies: #11456

[mstreng]

comment:12

I think the original author or reviewer could quickly review my patch. I only removed some stuff from the previous version, which already had a positive review...

[williamstein]

comment:13

Positive review of new version. Thanks for the rebase.

[nexttime]

Merged: sage-4.7.2.alpha3