Allowing HeckeAlgebraSymmetricGroupT to accept elements of SymmetricGroup(n) as input #37318
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…elements of SymmetricGroup
|
Independently of this patch, I wondered whether it might be better to depreciate
Both of these features could be added to IwahoriHeckeAlgebra (the jucys_murphy method would raise a NotImplemented error outside of types A and B, and possibly D, and lists in Permutation(n) can be distinguished from a list of generators). |
GiacomoPope
reviewed
Feb 13, 2024
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Documentation preview for this PR (built with commit 19ffe6c; changes) is ready! 🎉 |
vbraun
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Feb 18, 2024
…ents of SymmetricGroup(n) as input
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Currently, the following fails in sage:
```
sage: S4 = SymmetricGroup(4)
sage: H4 = HeckeAlgebraSymmetricGroupT(ZZ, 4)
sage: H4( Permutations(4).an_element() )
T[4, 1, 2, 3]
sage: H4( S4.an_element() )
Traceback (most recent call last)
...
TypeError: do not know how to make x (= (2,3,4)) an element of self
(=Hecke algebra of the symmetric group of order 4 on the T basis over
Univariate Polynomial Ring in q over Integer Ring)
```
I view this as a bug because the elements of this algebra are indexed by
elements of the symmetric group and `HeckeAlgebraSymmetricGroupT` does
accept elements of `Permutations(n)`.
This PR makes works work as well as accepting elements of
`Permutations(N)`, for `N>n, that fix `n+1,...,N`.
Previously, `HeckeAlgebraSymmetricGroupT` contain a `_coerce_start`
method. I have renamed this as `_element_constructor_`, which is what I
think it should be, and made some minor changes there. Probably, I
should deprecate `_coerce_start` but this method does not seem to exist
anywhere else in sage, so I suspect that this belongs to some code that
was deprecated years ago.
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### ⌛ Dependencies
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URL: sagemath#37318
Reported by: Andrew Mathas
Reviewer(s): Andrew Mathas, Giacomo Pope
vbraun
pushed a commit
to vbraun/sage
that referenced
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Feb 19, 2024
…ents of SymmetricGroup(n) as input
<!-- ^^^^^
Please provide a concise, informative and self-explanatory title.
Don't put issue numbers in there, do this in the PR body below.
For example, instead of "Fixes sagemath#1234" use "Introduce new method to
calculate 1+1"
-->
<!-- Describe your changes here in detail -->
Currently, the following fails in sage:
```
sage: S4 = SymmetricGroup(4)
sage: H4 = HeckeAlgebraSymmetricGroupT(ZZ, 4)
sage: H4( Permutations(4).an_element() )
T[4, 1, 2, 3]
sage: H4( S4.an_element() )
Traceback (most recent call last)
...
TypeError: do not know how to make x (= (2,3,4)) an element of self
(=Hecke algebra of the symmetric group of order 4 on the T basis over
Univariate Polynomial Ring in q over Integer Ring)
```
I view this as a bug because the elements of this algebra are indexed by
elements of the symmetric group and `HeckeAlgebraSymmetricGroupT` does
accept elements of `Permutations(n)`.
This PR makes works work as well as accepting elements of
`Permutations(N)`, for `N>n, that fix `n+1,...,N`.
Previously, `HeckeAlgebraSymmetricGroupT` contain a `_coerce_start`
method. I have renamed this as `_element_constructor_`, which is what I
think it should be, and made some minor changes there. Probably, I
should deprecate `_coerce_start` but this method does not seem to exist
anywhere else in sage, so I suspect that this belongs to some code that
was deprecated years ago.
<!-- Why is this change required? What problem does it solve? -->
<!-- If this PR resolves an open issue, please link to it here. For
example "Fixes sagemath#12345". -->
<!-- If your change requires a documentation PR, please link it
appropriately. -->
### 📝 Checklist
<!-- Put an `x` in all the boxes that apply. -->
<!-- If your change requires a documentation PR, please link it
appropriately -->
<!-- If you're unsure about any of these, don't hesitate to ask. We're
here to help! -->
<!-- Feel free to remove irrelevant items. -->
- [x] The title is concise, informative, and self-explanatory.
- [x] The description explains in detail what this PR is about.
- [x] I have linked a relevant issue or discussion.
- [x] I have created tests covering the changes.
- [x] I have updated the documentation accordingly.
### ⌛ Dependencies
<!-- List all open PRs that this PR logically depends on
- sagemath#12345: short description why this is a dependency
- sagemath#34567: ...
-->
<!-- If you're unsure about any of these, don't hesitate to ask. We're
here to help! -->
URL: sagemath#37318
Reported by: Andrew Mathas
Reviewer(s): Andrew Mathas, Giacomo Pope
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Currently, the following fails in sage:
I view this as a bug because the elements of this algebra are indexed by elements of the symmetric group and
HeckeAlgebraSymmetricGroupTdoes accept elements ofPermutations(n).This PR makes works work as well as accepting elements of
Permutations(N), forN>n, that fixn+1,...,N`.Previously,
HeckeAlgebraSymmetricGroupTcontain a_coerce_startmethod. I have renamed this as_element_constructor_, which is what I think it should be, and made some minor changes there. Probably, I should deprecate_coerce_startbut this method does not seem to exist anywhere else in sage, so I suspect that this belongs to some code that was deprecated years ago.📝 Checklist
⌛ Dependencies