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From: Ian Kelly <ian.g.kelly@gmail.com>
Date: Wed, 17 Sep 2014 09:35:54 -0600
Subject: Re: Why `divmod(float('inf'), 1) == (float('nan'), float('nan'))`
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On Tue, Sep 16, 2014 at 7:12 PM, Terry Reedy <tjreedy@udel.edu> wrote:
> It does not really matter, however, as infinity cannot be 'floored' as
> required for //
>
>>>> math.floor(float('inf'))
> Traceback (most recent call last):
>   File "<pyshell#21>", line 1, in <module>
>     math.floor(float('inf'))
> OverflowError: cannot convert float infinity to integer
>
> and hence
>
>>>> float('inf') // 1.0
> nan

In C, floor(INFINITY) returns infinity (at least in the implementation
I just tested).