#15289: Implement indexed monoids
-------------------------------------+-------------------------------------
Reporter: tscrim | Owner: sage-combinat
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-6.3
Component: algebra | Resolution:
Keywords: days54 | Merged in:
Authors: Travis Scrimshaw | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
public/monoids/15289-indexed | 1ff1a0483f5e61959a432371b701f593a5dee599
Dependencies: #15309 #15169 | Stopgaps:
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Changes (by tscrim):
* cc: SimonKing (added)
Comment:
Fixed everything mentioned above except I've run into a ''major'' pickling
issue with `UniqueFactory` (which is why I've cc-ed Simon).
There is some precedence for creating a generator from an index:
{{{
sage: C = CombinatorialFreeModule(ZZ, ['a','b','c'])
sage: C('a')
B['a']
}}}
So I'd like to leave that in for now. However I made things like `F(1)`
only return `F[1]`.
I changed the input for `Monoids().free(...)` but I left `FreeMonoid(...)`
as I had it before because I don't want to deal with deprecations there in
this ticket (this is #16330). I'll do the cleanup of the factory functions
in the followup #16329.
I'm not doing anything to `FreeMonoid` or `FreeAbelianMonoid` other than
redirecting input, so I'm not going to make these changes here:
> * Now or later: __repr__ -> _repr_, __call__ -> _element_constructor_.
The custom __contains__ might not be needed.
> * Now or later: initialize the category
We could probably also fit that in #16329 or another followup.
Simon, so I've changed the `UniqueFactory` object `FreeMonoid` to a new
factory function since it returns a class which I've designed as a
`UniqueRepresentation`. However unpickling old `FreeMonoid` objects fails
because of the unpickling mechanism of `UniqueFactory` redirects to
`generic_factory_unpickle()` and has `FreeMonoid` from the global
namespace as the first object. It is expecting it to be a `UniqueFactory`
instance, so it errors out here. Furthermore because of the structure of
the pickle, I'm unable to use `register_unpickle_override` or see anyway
to redirect that specific pickle without changing the behavior of
`generic_factory_unpickle()`.
I'm thinking the best thing to do is to change
`generic_factory_unpickle()` to accept a general object as input and if
the first input is no longer a `UniqueFactory`, then call it with the
arguments given as part of the pickle. Another option I see is to override
`UniqueFactory.__call__`, but I really don't want to do that. The last
option I see, and I absolutely don't like this, is to make my new factory
function into a different name temporarily (or deprecate `FreeMonoid`
construction altogether). Any ideas?
I'm also thinking we should change this behavior so we don't keep running
into this problem.
--
Ticket URL: <http://trac.sagemath.org/ticket/15289#comment:36>
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