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From: Marko Rauhamaa <marko@pacujo.net>
Newsgroups: comp.lang.python
Subject: Re: Problems using struct pack/unpack in files, and reading them.
Date: Sat, 14 Nov 2015 18:52:56 +0200
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Ian Kelly <ian.g.kelly@gmail.com>:

> For somebody reading one of these uses of unary plus in real code, I
> imagine it would be a bit of a WTF moment if it's the first time
> they've encountered it. I don't recall ever seeing any code that
> actually used this, though.

What I don't understand is why there is a unary + but no unary /:

   -x ≡ 0 - x
   +x ≡ 0 + x
   /x ≡ 1 / x
   //x ≡ 1 // x
   *x ≡ 1 * x

You could write:

   r = //(//r1 + //r2 + //r3)

for

   r = 1 // (1//r1 + 1//r2 + 1//r3)

Actually, the real question is, is the unary - *really* so useful that
it merits existence or is it just something that was mindlessly copied
into programming languages from elementary school arithmetics?

BTW, Scheme's got the whole set:

    (- 3)
    => -3
    (- 3 2)
    => 1
    (- 3 2 1)
    => 0
    (/ 3)
    => 1/3
    (* 3)
    => 3
    (*)
    => 1

However, there's a tricky discontinuity:

    (apply - 3 '(2 1))
    => 0
    (apply - 3 '(2))
    => 1
    (apply - 3 '())
    => -3


Marko