FixedPoint

[Robin Becker]

It is perfectly clear that it's OK to ask if f==None for any f. The
whole point about the row over integer division was that it's ok to pass
different types into code and that code should behave reasonably under
all circumstances.

if 5.0==None ==> 0

then making FixedPoint(5.0)==None raise an exception is pretty
pointless.

A typical technique is to have a default argument value of None and use
that correspondence to initialise in some special way.
-- 
Robin Becker