I have in the meantime tracked this to ComplexIntervalField and
RealIntervalField both overriding __call__ in a way that seems to preempt
usual coercion from working.
Note that CIF(s2) fails, but CIF.coerce(s2) works just fine. It seems that
CIF/RIF just end up calling
ComplexIntervalFieldElement.__init__()/RealIntervalFieldElement.__init__()
with whatever you pass (s2 in this case).
RealIntervalFieldElement.__init__() will in a last-ditch effort do:
# try coercing to real
try:
rn = self._parent._lower_field()(x)
rn1 = self._parent._upper_field()(x)
except TypeError:
raise TypeError, "Unable to convert number to real interval."
which ends up invoking the coercion framework to coerce s2 from
K2->RR->RIF. ComplexIntervalFieldElement.__init__ seems to assume that `s2`
is in fact just a real part, and fails to do something reasonable with it.
Can somebody familiar with how coercion is supposed to work confirm that
the problem is that RIF/CIF are using some old variant instead of the
coercion framework (if I read the documentation right one is supposed to
override _element_constructor in favor of __call__)?
- Daniel
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