Hi,
sorry, guys; I woke up to 20 replies and I probably need to catch up
first, but as I need to catch a plane, let me throw in my 2 cents now.
Can we make Composition.sum() a classmethod rather than a
staticmethod? I don't understand why it is not currently a
classmethod. This isn't sane:
sage: Composition([1,2]).sum([Composition([3]),Composition([4])])
[3, 4]
This is not to say that Sage's overriding of sum() (the global
function, not the Composition method) is good craftsmanship. This
piece of code in sage/misc/functional.py:
if hasattr(expression, 'sum'):
return expression.sum(*args, **kwds)
is basically a heuristic. There should be no heuristics involved in a
sum method.
What again is the difference between Python's add() and Python's sum()
? Or is add() a Sage alias for sum() ? And how exactly does overriding
__add__ sabotage coercion? By not letting the return value be coerced
into the right class? If so, this might be intended. At least on
partitions, there are many operations which explicitly should not cast
their return value into the same subclass their input values came
from; I imagine the same making sense on compositions (the
concatenation of two compositions-of-length-less-or-equal-3 needs not
be a such).
Best regards,
Darij
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