"return NotImplementedError" in ring.pyx

[williamstein]

On Wed, Nov 25, 2009 at 7:26 PM, John H Palmieri <jhpalmieri64@gmail.com> wrote:
> In ring.pyx, there is code like this:
>
>        if proof:
>            return NotImplementedError
>        else:
>            return False
>
> I would think that the second line should say "raise
> NotImplementedError".  (Changing it makes some doctests fail,
> though.)  Is there a good reason for doing "return
> NotImplementedError"?

That's *definitely* a bug.   No question about it. 

Addendum: apply the patches trac_7532.patch and trac_7532-rings.patch. Depends on #7535.

Component: elliptic curves

Author: John Cremona

Reviewer: Tim Dumol, John Palmieri

Merged: sage-4.3.2.alpha0

Issue created by migration from https://trac.sagemath.org/ticket/7532

[sagetrac-ylchapuy]

comment:1

grep gives:

• ./symbolic/expression.pyx: return NotImplementedError
• ./symbolic/expression_conversions.py: return NotImplementedError("SymPy function '%s' doesn't exist" % f)
• ./rings/ring.pyx: return NotImplementedError
• ./modular/arithgroup/congroup_gammaH.py: return NotImplementedError
• ./geometry/polyhedra.py: return NotImplementedError

[sagetrac-ylchapuy]

comment:2

and allowing other error types we get:

• ./interfaces/gap.py: return RuntimeError, "Error evaluating %s in %s"%(line, self)
• ./modular/abvar/finite_subgroup.py: return ValueError, "self and other must be in the same ambient Jacobian"
• ./groups/perm_gps/permgroup_named.py: return ValueError, "Degree must be 2."
• ./groups/perm_gps/permgroup_named.py: return ValueError, "Degree must be 2."

[sagetrac-ylchapuy]

comment:3

and also (my grep has a strange behavior..?):

*./structure/element.pyx: return ArithmeticError, "Multiplicative order of 0 not defined."
*./rings/finite_field_givaro.pyx: return ArithmeticError, "Multiplicative order of 0 not defined."

[jhpalmieri]

comment:4

See also #7535.

[TimDumol]

Work Issues: Close if #7535 does

[jhpalmieri]

comment:6

Given the patches at #7535, the one remaining case of this is the one in ring.pyx. If I make the change from

return NotImplementedError

to

raise NotImplementedError

there, I get doctest failures in the files

	sage -t -long "devel/sage/sage/schemes/elliptic_curves/monsky_washnitzer.py"
	sage -t -long "devel/sage/sage/schemes/elliptic_curves/padics.py"
	sage -t -long "devel/sage/sage/schemes/elliptic_curves/sha_tate.py"

and maybe some others in this directory.

[jhpalmieri]

Changed work issues from Close if #7535 does to none