[Python-ideas] Suggestion: Extend integers to include iNaN

Kyle Lahnakoski klahnakoski at mozilla.com
Sun Sep 30 10:31:11 EDT 2018

On 2018-09-30 10:15, David Mertz wrote:
> For similar reasons, I'd like an iInf too, FWIW.  It's good for an
> overflow value, although it's hard to get there in Python ints (would
> 'NaNAwareInt(1)/0' be an exception or iInf?).  Bonus points for anyone
> who knows the actual maximum size of Python ints :-).
> However, the main use I'd have for iInf is simply as a starting value
> in a minimization loop.  E.g.
>     minimum = NaNAwareInt('inf')
>     for i in the_data:
>         minimum = min(i, minimum)
>         other_stuff(i, minimum, a, b, c)
> I've written that code a fair number of times; usually I just pick a
> placeholder value that is "absurdly large relative to my domain", but
> a clean infinity would be slightly better.  E.g. 'minimum = 10**100'.

If we conceptualize iNan as "not an integer", then we can define
operators in two manners:

Let |●| be any operator:

1) "conservative" - operators that define a|● |b==iNaN if either a or b
is iNan
2) "decisive" - operators that never return iNan

With a decisive min(a, b), you can write the code you want without
needing iINF


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