LinearMatroid.has_line_minor should catch NotImplementedError
The following code should not throw an error:
sage: R.<x,y> = ZZ['x','y']
sage: Q = R.quotient([x^2  y + 1, y^3 + 3 * x  7])
sage: M = LinearMatroid(ring=Q, reduced_matrix=Matrix([[1,0,1],[0,1,1]]))
sage: M.has_line_minor(3)
Traceback (most recent call last):
...
NotImplementedError:
Easy solution: add NotImplementedError? to the except clause in the code.
Change History (6)
Component: 
PLEASE CHANGE →
matroid theory

Milestone: 
sage6.1 →
sage6.2

Branch: 
→ u/Rudi/ticket/15295

Created: 
Oct 16, 2013, 7:28:49 PM →
Oct 16, 2013, 7:28:49 PM

Modified: 
Jan 30, 2014, 9:20:52 PM →
Jan 30, 2014, 9:20:52 PM

Commit: 
→ dd3ad7d2943d03db3ad8e1001362704ece1ed77b

Status: 
new →
needs_info

Milestone: 
sage6.2 →
sage6.3

Milestone: 
sage6.3 →
sage6.4

Added that exception clause. Now the same example raises another NotImplementedError?, but one that gives more information. Essentially, computing ratios in that given ring Q is not possible, which is a problem in LinearMatroid?._line_ratios().
So what is the policy here? Should has_line_minor() test if computing inverses is possible before handing the problem down?
New commits:
Added an exception clause to catch a NonImplementedError below LinearMatroid.has_minor()