[Python-ideas] Changing Decimal.__pos__ and Decimal.__neg__ [Was: Re: Python Numbers as Human Concept Decimal System]

[Mark Dickinson]

On Mon, Mar 10, 2014 at 7:08 PM, Tim Peters <tim.peters at gmail.com> wrote:

> Looks like Mike C's intent was that
>
>     +x
>
> act like
>
>     Decimal(0) + x
> [...]


Yes, I'm pretty sure that's what he intended.  It's clearly spelled out in
the standard: "the operations plus(a) and minus(a) (where a and b refer to
any numbers) are calculated as the operations add(’0’, a) and subtract(’0’,
b)respectively", but not in our docs.

Can't win!  That -x loses the sign when x is a positive 0 (under most
> rounding modes) is jarring; but that the results of "-x" and "0-x" may
> not be the same would also be jarring.
>

Hmm. I find the second option a lot less jarring than the first, but maybe
that's because I'm used to it (and because I'm too young to really remember
non-IEEE floating-point formats; the only one I really encountered was the
Sinclair ZX81's 40-bit format).

Not a fan of signed zeroes :-(
>

Yeah, me neither, but with IEEE 754 world domination it looks like they're
here to stay.

Mark
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