[sage-combinat-devel] CartanTypes
Sorry if I should post this to sage-support ...
Does CartanType currently support A_\infty? I checked the docs and it seems
not but I wanted to check because I need this. Well, actually, I only need
some very rudimentary combinatorial data from the Cartan type, that I can
easily manufacture myself, but thematically I really should index the
objects that I am playing with by the appropriate Cartan types as I am
hoping that what I am doing will work in types A^{(1)}_l, A^{(2)}_{2l},
C^{(1)}_l, D^{(2)}_l and A_\infty.
Whilst looking for this I came across the following, which I guess are
syntax errors on my part rather than bugs:
sage: CartanType(['A',4,1]) # works
['A', 4, 1]
sage: CartanType(['A',infinity])
File "", line unknown
^
SyntaxError: unexpected EOF while parsing
sage: CartanType(['A',-1])
File "", line unknown
^
SyntaxError: unexpected EOF while parsing
sage: CartanType(['A',0])
['A', 0]
Andrew
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Re: [sage-combinat-devel] CartanTypes
Dear Andrew,
On Tue, Jul 05, 2016 at 11:10:46AM -0700, Andrew wrote:
>Sorry if I should post this to sage-support ...
This sounds like the right place to discuss it!
>Does CartanType currently support A_\infty? I checked the docs and it
>seems not but I wanted to check because I need this. Well, actually, I
>only need some very rudimentary combinatorial data from the Cartan
>type, that I can easily manufacture myself, but thematically I really
>should index the objects that I am playing with by the appropriate
>Cartan types as I am hoping that what I am doing will work in types
>A^{(1)}_l, A^{(2)}_{2l}, C^{(1)}_l, D^{(2)}_l and A_\infty.
Currently, there is no support for `A_\infty`. This is mostly because
most of the interesting stuff that a cartan type provides in Sage
(e.g. the Cartan matrix, ...) is returned as a non lazy object.
Could you provide a couple examples of use that you have in mind?
In the simplest form, returning a formal object with very few methods
implemented (maybe just `is_crystalographic` and friends) would be
straightforward: add a file type_A_infinity.py with a CartanType class
and whatever you want inside it, and update CartanType.__call__ to use
it as appropriate.
>Whilst looking for this I came across the following, which I guess are
>syntax errors on my part rather than bugs:
>sage: CartanType(['A',4,1]) # works
>['A', 4, 1]
>sage: CartanType(['A',infinity])
> File "", line unknown
>^
>SyntaxError: unexpected EOF while parsing
>sage: CartanType(['A',-1])
> File "", line unknown
>^
>SyntaxError: unexpected EOF while parsing
>sage: CartanType(['A',0])
>['A', 0]
What's happening here is that the above does not fit within the
standard input formats that Cartan type accepts; and then it gets
confused and tries to parse the string in search of one of our
shortcuts like CartanType("A3*xA2~"). Yeah, this is a bug: it should
instead return a proper not implemented error.
Cheers,
Nicolas
--
Nicolas M. Thiéry "Isil"
http://Nicolas.Thiery.name/
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Re: [sage-combinat-devel] CartanTypes
On Wednesday, 6 July 2016 16:20:12 UTC+1, Nicolas M. Thiery wrote:
>
> Dear Andrew,
>
> Currently, there is no support for `A_\infty`. This is mostly because
> most of the interesting stuff that a cartan type provides in Sage
> (e.g. the Cartan matrix, ...) is returned as a non lazy object.
>
> Could you provide a couple examples of use that you have in mind?
>
Thanks Nicolas!
At this point I only need the rank and to be able differentiate A_oo from
other types. Down the track it might be useful to have the weight and root
lattices but again I don't really need them. Mostly I'd like CartanType()
to support A_oo for compatibility with the other types that I am playing it.
>
> In the simplest form, returning a formal object with very few methods
> implemented (maybe just `is_crystalographic` and friends) would be
> straightforward: add a file type_A_infinity.py with a CartanType class
> and whatever you want inside it, and update CartanType.__call__ to use
> it as appropriate.
>
Thanks for the description of what needs to be done. I'll throw something
together and sort out the bug below.
Andrew
> >Whilst looking for this I came across the following, which I guess
> are
> >syntax errors on my part rather than bugs:
> >sage: CartanType(['A',4,1]) # works
> >['A', 4, 1]
> >sage: CartanType(['A',infinity])
> > File "", line unknown
> >^
> >SyntaxError: unexpected EOF while parsing
> >sage: CartanType(['A',-1])
> > File "", line unknown
> >^
> >SyntaxError: unexpected EOF while parsing
> >sage: CartanType(['A',0])
> >['A', 0]
>
> What's happening here is that the above does not fit within the
> standard input formats that Cartan type accepts; and then it gets
> confused and tries to parse the string in search of one of our
> shortcuts like CartanType("A3*xA2~"). Yeah, this is a bug: it should
> instead return a proper not implemented error.
>
> Cheers,
> Nicolas
>
>
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