Behaviour of the order function for infinite groups

[sagetrac-ljpk]

When one tries to use the order function on group elements of infinite order, one gets an error:

gl=GL(2,ZZ)
g=gl.gens()[2]
g.order()

In MAGMA, one (often) gets the answer 0 if one calls the Order function on elements of infinite order.

Component: linear algebra

Issue created by migration from https://trac.sagemath.org/ticket/1170

[JohnCremona]

Attachment: 1170-matrix-group-order.patch.gz

[JohnCremona]

comment:1

The patch fixes this: for consistency with other groups, +Infinity is returned as the order for group elements of infinite order. A doctest has been added.

The patch should apply to 3.1.2.alpha4 and later, and all doctests in sage.groups pass.

Review, Lloyd?

[sagetrac-mabshoff]

comment:3

One small nitpick which I corrected in the patch I applied: The # in the doctests need to be escaped, i.e.

See trac \#1170

I am not sure if this applies in case the docstring is not raw, but let's do it so that downroad we do not get bitten by it.

Cheers,

Michael

[sagetrac-mabshoff]

comment:4

Merged in Sage 3.1.2.rc0