#16553: Clean IncidenceStructure
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Reporter: vdelecroix | Owner:
Type: enhancement | Status: needs_info
Priority: major | Milestone: sage-6.3
Component: combinatorial | Resolution:
designs | Merged in:
Keywords: | Reviewers:
Authors: Nathann Cohen, | Work issues:
Vincent Delecroix | Commit:
Report Upstream: N/A | a5c4dbc9d1b77315d90dd3dd7a8ccea780f59ecf
Branch: public/16553 | Stopgaps:
Dependencies: |
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Comment (by vdelecroix):
Replying to [comment:15 ncohen]:
> Yo !
>
> > The definition of block design used in Sage is wrong. A block design
is a synonym for incidence structure (as it can be checked on wikipedia or
the Handbok of combinatorial designs). What was considered are t-designs
for which you have well defined parameters `t-(v,k,\lambda)`. It is a
particular case of block design. Hopefully right now there is only one
class and making `BlockDesign = IncidenceStructure` looks safe enough to
me.
>
> Well, right now tdesign returns an incidence structure too. Okay, one
question : should we deprecate !BlockDesign in favor of
!IncidenceStructure ? Also, it seems weird to have an upper case T in
TDesign, given that this "t" is a variable.... What about tDesign ?
> What I don't like about this is that we do not need a tDesign class at
all, so why would we create one ? We create classes for the wrong reason
and we have nothing to put in them.
I propose to remove tDesign and have `IncidenceStructure` (in
`incidence_structure.py`) and set `BlockDesign = IncidenceStructure` as an
alias (in `block_design.py`).
> > The only stuff I added is just to simplify the `is_t_design` function
(like `t_indices`, `replication_numbers`, etc).
>
> I have never heard of "t indices" anywhere. Where did you find this
terminology ? It just seems to be the degree of a point, taken as a
hypergraph ...
Handbook definition I.1.5. If it is not standard I can change it. To me,
`degree` looks more natural.
--
Ticket URL: <http://trac.sagemath.org/ticket/16553#comment:16>
Sage <http://www.sagemath.org>
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