#15475: Reenable broken doctests in #15473 and #15476 when #10963 is merged
-------------------------------------+-------------------------------------
Reporter: darij | Owner:
Type: defect | Status: needs_work
Priority: minor | Milestone: sage-6.3
Component: categories | Resolution:
Keywords: 10963, | Merged in:
categories, c3, coercion, | Reviewers:
transitivity, descent algebras, | Work issues:
symmetric functions | Commit:
Authors: | ef918e33132d7bf77dd999696a0efd891d831377
Report Upstream: N/A | Stopgaps:
Branch: |
public/categories/15475 |
Dependencies: #10963, #15473, |
#15476 |
-------------------------------------+-------------------------------------
Changes (by darij):
* keywords: 10963, categories, c3 =>
10963, categories, c3, coercion, transitivity, descent algebras,
symmetric functions
Comment:
OK, here is a minimal(?) way to cause the bug. Copy this code:
{{{
def descent_test(n):
DA = DescentAlgebra(QQ, n)
DAD = DA.D()
DAB = DA.B()
DAD([])
for I in Compositions(n):
DAD(DAB[I])
def maintest():
descent_test(3)
descent_test(4) # you need both 3 and 4, IN THIS ORDER, to break it!
SGA4 = SymmetricGroupAlgebra(QQ, 4)
DAB = DescentAlgebra(QQ, 4).B()
x = DAB[4]
SGA4(x)
}}}
into a .py file and attach it. Run maintest(). You will get an error:
{{{
TypeError: do not know how to make x (= B[4]) an element of self
(=Symmetric group algebra of order 4 over Rational Field)
}}}
Afterwards, try doing
{{{
sage: SGA4 = SymmetricGroupAlgebra(QQ, 4)
sage: D4 = DescentAlgebra(QQ, 4).D()
sage: SGA4.has_coerce_map_from(D4)
}}}
You get `False`, although in a virgin session it would be `True`. So it
looks like either we have problems with UniqueRepresentation and coercion,
or the coercion graph has become too confusing for Sage to find a way.
How do I debug a failed coercion? Is there a method that shows me a local
coercion graph?
Although, I am no longer sure if the sfa.py issue has really been fixed or
if #10963 has just kicked the can further down the road. Is there a sanity
check for coercion graphs?
--
Ticket URL: <http://trac.sagemath.org/ticket/15475#comment:13>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
--
You received this message because you are subscribed to the Google Groups
"sage-trac" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at http://groups.google.com/group/sage-trac.
For more options, visit https://groups.google.com/d/optout.
