#12977: Let singular_function expect "attributes" not as a dict
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Reporter: SimonKing | Owner: malb
Type: defect | Status: needs_work
Priority: major | Milestone: sage-5.1
Component: commutative algebra | Resolution:
Keywords: sd40.5 | Work issues:
Report Upstream: N/A | Reviewers: Mike Hansen
Authors: Simon King | Merged in:
Dependencies: | Stopgaps:
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Comment (by SimonKing):
Replying to [comment:9 robertwb]:
> a_attrib will be defined after any non-empty loop even if it doesn't
break with a match
I don't understand that comment. a_attrib is used only in the few lines
that I changed. And what loop are you talking about? The outer loop `for a
in args:` (line 559)? But a_attrib is set to None at each round of the
outer loop: See the new line 630.
> I think that this interface is rather subtle, I'd rather have a
compare_using_identiy=[True|False] keyword in the function (which will
iterate over the dictionary rather than indexing into it).
One could argue that by using the dictionary (i.e., the old syntax) you
declare that you want comparison by equality rather than identity. And
also note that in Singular you assign an attribute to an individual ideal;
hence, I find it wrong that in Sage we assign the attributes to an
equivalence class of ideal.
> On that note, is indexing ever safe (do equal ideals always hash the
same?)
No, as mentioned in the ticket description, the hash is totally broken
(#12976). Two polynomial ideals are equal if they have the same reduced
Gröbner basis (computed in degrevlex order, if the GB for the "real" order
ist not in the cache), but the hash relies on the given generators. That's
why I support the old syntax only for backwards compatibility.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12977#comment:10>
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