Well I'm finally somewhere I can write an e-mail from easily, though I
haven't had the time to reread the thread. The issue I considered in the
past like this was operations like "speye(n) .^ 0" or "speye(n) ./ 0" where
the 0.^0 and 0./0 terms of the matrix should create a NaN in the resulting
matrix I hadn't considered the "speye(n) OP NaN" but didn't and don't yet
see why it should be different if the NaN is pre-existing rather than
created by the binary operation, otherwise the NaN values won't propagate
and in fact might very likely disappear. You seem to think, and have
convince John that disappearing NaN's are a good thing so I'll try to reread
the thread and respond again later on.