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From: Chris Angelico <rosuav@gmail.com>
Newsgroups: comp.lang.python
Subject: Re: for / while else doesn't make sense
Date: Mon, 23 May 2016 01:32:07 +1000
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On Mon, May 23, 2016 at 1:19 AM, Steven D'Aprano <steve@pearwood.info> wrote:
> Okay, now I'm confused. How is 1/2 returning 0.5 the language not doing what
> you've told it to do?

That isn't the problem. With binary floats, 1/2 can be perfectly
represented, so you have no trouble anywhere. The problem comes when
you then try 1/5. What do you get? 3602879701896397/18014398509481984.
Python shows that as 0.2. Then you do some more arithmetic, and the
veil is pierced, and you discover that 1/5 doesn't actually return
0.2, but just something really really close to it - which it tells you
is 0.2.

I'm not saying that having 1/5 return 0 is better, but I'd like a
broad acceptance that 0.2 is imperfect - that, in fact, *every* option
is imperfect.

ChrisA