Q about tail recursion

[François Pinard]

Robin Becker <robin at jessikat.demon.co.uk> écrit:

> François Pinard> <pinard at iro.umontreal.ca> writes:

> > `None' is a Python natural for a "missing" result [...]

> I agree about efficiency.  I guess I could make my own error values eg
> SeriesMissing or whatever.

I guess one could also write `missing = None', and use `missing' instead,
for clarity.

In one application I wrote (a firewall generator, in fact), a set of
variables occur all around to represent various restrictions.  When there
is no restriction (or if you prefer, when the restriction is "missing"),
I use the value `None'.  But using the word `None' to mean there is no
restriction is confusing, as it suggests that "None is allowed", while the
connotation should rather be that "Any is allowed".  So I picked `Any' as
a kind of more legible keyword.  At the beginning of the program, there is:

    Any = None

which surely looks a bit surprising, at first. :-)

-- 
François Pinard   http://www.iro.umontreal.ca/~pinard