Ideal with no generators for univariate polynomial rings

[sagetrac-mraum]

Consider the following (Sage 4.7alpha1) :

sage: P.<a> = QQ[]
sage: P.ideal([])
Booom!

The issue is twofold: The ideal method in rings/rings.py is called and does not accept an empty list. But also the univariate polynomial rings should call a specialized method just like the multivariate ones do.

It worked in earlier versions (like 4.2 or so) and is a construction that easily comes up as a corner case.

Apply attachment: 11139_alternative.patch.

Component: commutative algebra

Author: Martin Raum, Jeroen Demeyer

Reviewer: John Palmieri, Martin Raum

Merged: sage-4.7.1.alpha1

Issue created by migration from https://trac.sagemath.org/ticket/11139

[sagetrac-mraum]

Attachment: trac-11139-ideals_with_no_generators.patch.gz

[jhpalmieri]

Author: Martin Raum

[jhpalmieri]

Reviewer: John Palmieri

[jhpalmieri]

comment:1

I'm happy with this. Here's a new patch with a few doctests illustrating that the problem has been fixed.

I'm going to mark this as "needs review"; it wouldn't hurt to have someone else look it over.

[jhpalmieri]

Attachment: trac-11139-ideals_with_no_generators.v2.patch.gz

[jhpalmieri]

Description changed:

--- 
+++ 
@@ -11,3 +11,8 @@
 I make this a block, as it worked in earlier versions (like 4.2 or so) and is a construction that easily comes up as a corner case.
 
 The patch attached solves the issue, but it is a patch created in 30 seconds. I am sorry that I currently don't have time to deal with this.
+
+---
+
+Apply [attachment: trac-11139-ideals_with_no_generators.v2.patch](https://github.com/sagemath/sage-prod/files/10652590/trac-11139-ideals_with_no_generators.v2.patch.gz).
+

[jdemeyer]

Description changed:

--- 
+++ 
@@ -14,5 +14,5 @@
 
 ---
 
-Apply [attachment: trac-11139-ideals_with_no_generators.v2.patch](https://github.com/sagemath/sage-prod/files/10652590/trac-11139-ideals_with_no_generators.v2.patch.gz).
+Apply [attachment: 11139_alternative.patch](https://github.com/sagemath/sage-prod/files/10652591/11139_alternative.patch.gz).
 

[jdemeyer]

Changed author from Martin Raum to Martin Raum, Jeroen Demeyer

[jdemeyer]

comment:3

What do you think of this alternative patch? IMHO, it has better logic.