FYI, I have fixed .nabla(), plethysm() and .inner_plethysm() (and maybe one 
or two other cases) where the base case of s(0) needs to be handled 
differently in some recent updates to my patch and I added doc tests which 
check this case and s(1) (although this one never gave me a problem).  I'll 
never know for sure if I caught them all.  Instead it would be better 
if ._apply_module_morphism() worked as expected if the self.is_zero() is 
True and the indexing set is infinite.

Franco, if I understand right, then s(0).nabla() would then raise an error 
(before my patch is applied).  I still think then that there is another fix 
to be done on ._apply_module_morphism().

-Mike

On Friday, 15 June 2012 01:32:01 UTC-4, Anne Schilling wrote:
>
> On 6/14/12 8:37 PM, Franco Saliola wrote: 
> > On Mon, Jun 11, 2012 at 10:54 PM, Mike Zabrocki <[email protected]> 
> wrote: 
> >> Hi all, 
> >> 
> >> In running some symmetric function code I ran across the problem that 
> my 
> >> code started freezing somewhere in the middle of the calculation. 
> >> I tracked it down and I had assumed that it was in the changes that I 
> had 
> >> made to the symmetric function code.  Nope.  I went back to sage main 
> and 
> >> could recreate the same issue.  I was also able to recreate the same 
> sort of 
> >> issue with plethysm and inner_plethysm. 
> >> 
> >> Easy fix: if value .is_zero() don't call the ._apply_module_morphism() 
> >> Second easy fix: if value .is_zero() have ._apply_module_morphism() 
> return 0 
> >> 
> >> But is the problem deeper? 
> > 
> > It seems so. 
> > 
> >> I found the code is freezing because ._apply_module_morphism is calling 
> the 
> >> following recreate-able issue: 
> >> 
> >> sage: s = SymmetricFunctions(QQ).s() # or s = SFASchur(QQ) in sage-main 
> >> sage: list( s.basis() ) 
> > 
> > I was playing around with this in sage with all the combinat patches 
> > applied, and it actually returns an error: 
> > 
> >     sage: s = SymmetricFunctions(QQ).s() 
> >     sage: b = s.basis() 
> >     sage: list(b) 
> >     Traceback (most recent call last): 
> >     ... 
> >     NotImplementedError: infinite list 
>
> Strange, when I try this I do not get an error message and it just runs. 
> But I only have the patches up to kschur-fix-as.patch applied. 
>
> Cheers, 
>
> Anne 
>
>

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