#3979: Power series composition messes up precision
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Reporter: kedlaya | Owner: somebody
Type: defect | Status: needs_work
Priority: critical | Milestone: sage-4.7.1
Component: algebra | Keywords: power series, composition, precision
Work_issues: | Upstream: N/A
Reviewer: | Author: Francis Clarke
Merged: | Dependencies:
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Changes (by kedlaya):
* status: needs_review => needs_work
Comment:
The patch looks reasonable on its own. However, changing the call syntax
for power series generates quite a number of doctest failures elsewhere,
by triggering the error message
{{{
ValueError: Cannot substitute this value
}}}
Here are the examples I found in the rings and schemes directories; there
may be more elsewhere that I didn't find. (This used 4.7.1.rc1, but I
don't think the version much matters.)
{{{
sage -t "devel/sage/sage/rings/multi_power_series_ring.py"
sage -t "devel/sage/sage/rings/laurent_series_ring_element.pyx"
sage -t "devel/sage/sage/rings/multi_power_series_ring_element.py"
sage -t "devel/sage/sage/rings/power_series_ring.py"
sage -t
"devel/sage/sage/schemes/hyperelliptic_curves/hyperelliptic_generic.py"
sage -t
"devel/sage/sage/schemes/hyperelliptic_curves/hyperelliptic_padic_field.py"
sage -t "devel/sage/sage/schemes/elliptic_curves/ell_wp.py"
sage -t "devel/sage/sage/schemes/elliptic_curves/formal_group.py"
sage -t "devel/sage/sage/schemes/elliptic_curves/ell_rational_field.py"
sage -t "devel/sage/sage/schemes/elliptic_curves/padic_lseries.py"
sage -t "devel/sage/sage/schemes/elliptic_curves/padics.py"
}}}
This patch can't receive a positive review with all these broken doctests.
The best thing would be to fix them all now, but if that is infeasible, I
would propose the following.
1. Deprecate the old syntax: accept it while raising a
`DeprecationWarning`.
2. Once this ticket is closed, open a second ticket to modify the syntax
in the other doctests.
3. Once the second ticket is closed, open a third ticket to remove the old
syntax.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/3979#comment:5>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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