#9181: Update dev-guide : __hash__ return a long
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Reporter: hivert | Owner: mvngu
Type: defect | Status: new
Priority: major | Milestone: sage-4.4.4
Component: documentation | Keywords:
Author: Florent Hivert | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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From sage-devel
{{{
> 1. I think we should update the devguide, or is there something I don't
get ?
No, we should update the developers guide. Despite this sentence, the (c)
return type of "hash" has been a long since Python 2.3 at least, so I
think
this wasn't ever correct for 64-bit long machines. (What was required is
that it fit into a Python int.)
> 2. I'm writing a Cython class which caches the hash value. Which type
> should I
> use for the attribute ? int doesn't work since when trying to store
the
> hash of None in an int I get
>
> OverflowError: value too large to convert to int
>
> Is long ok and portable (it is was is used in a few place in sage) ?
> Should
> we write it in the doc ?
Yes, we should be using C longs here. Under the hood
Python int = C long != C int
Python float = C double != C float
and Python longs have no (native) C equivalent.
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9181>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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