Question about None

Rhodri James rhodri at
Sat Jun 13 17:22:14 EDT 2009

On Sat, 13 Jun 2009 21:25:28 +0100, John Yeung  
<gallium.arsenide at> wrote:

>> > But mathematically speaking, it's intuitive that
>> > "nothing" would match any type.
>> Completely wrong.  The concept you're thinking of in
>> denotational semantics is called "bottom", but bottom
>> is not a value that functions can compute and return.
>>  It is really the absence of a value.
> I've never heard a mathematician use the term "bottom".  It certainly
> could be that I just haven't talked to the right types of
> mathematicians.  I'm not sure it's even relevant.  "Denotational
> semantics" is specific to computer science.  My point was simply that
> even an elementary understanding of mathematics (and I'll grant a
> naive understanding of computer science as well) might lead someone to
> think that it *might* make sense for None to be the name for nothing.

Such an understanding would be clearly wrong in the context in which we
were talking (and denotational semantics is a branch of category theory,
which is not specific to computer science if you don't mind).  If None
is nothing, then it can't be a string, int, float or anything else,
because they're all something.

Rhodri James *-* Wildebeest Herder to the Masses

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