#8197: Documenting check=True/False parameters
----------------------------------+-----------------------------------------
Reporter: cremona | Owner: AlexGhitza
Type: defect | Status: new
Priority: major | Milestone: sage-4.3.3
Component: algebraic geometry | Keywords:
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
----------------------------------+-----------------------------------------
Comment(by fwclarke):
Replying to [ticket:8197 cremona]:
> The point is that on creation of the point, valid tuple input is
converted to a list, unless check=False in which case tuples are left as
tuples.
John, it's not quite accurate what you say:
{{{
sage: P2 = ProjectiveSpace(GF(2),2)
sage: type(P2.point([0,0,1])._coords)
<class 'sage.structure.sequence.Sequence'>
sage: type(P2.point([0,0,1], check=False)._coords)
<type 'list'>
}}}
even though
{{{
sage: P2.point([0,0,1], check=False) == P2.point([0,0,1])
True
}}}
The relevant code is for the class
`SchemeMorphism_projective_coordinates_field` in
`schemes/generic/morphism.py :` with `check=False,` absolutely nothing is
done except for setting the attribute `_coords`. Thus
{{{
sage: P = P2.point("Anything", check=False)
sage: P._coords
'Anything'
sage: P
('A' : 'n' : 'y' : 't' : 'h' : 'i' : 'n' : 'g')
}}}
So, strictly speaking, the coordinates have to be given as a `Sequence` of
the right length.
I think you're right that the key thing is documentation. In each case
there's a design balance to be drawn (when `check=False`) between on the
one hand checking nothing at all and on the other making some basic
conversions, while not doing time-consuming things such as, for example,
verifying that an input satisfies a polynomial. How this balance is drawn
will vary, but the INPUT block ought make it clear how the requirements
depend on the value of `check`.
The relevant part of the documentation for
`SchemeMorphism_projective_coordinates_field` says
{{{
- ``v`` - a list or tuple of coordinates in K
}}}
The code shows that this is actually too restrictive when `check` is True,
and it is inaccurate when check is False.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/8197#comment:2>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
--
You received this message because you are subscribed to the Google Groups
"sage-trac" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/sage-trac?hl=en.
