% is not an operator [was Re: Verbose and flexible args and kwargs syntax]

[Eelco]

On Dec 15, 11:47 am, Robert Kern <robert.k... at gmail.com> wrote:
> On 12/14/11 12:32 PM, Steven D'Aprano wrote:
>
> > On Wed, 14 Dec 2011 10:56:02 +0200, Jussi Piitulainen wrote:
> >> I'm not misunderstanding any argument. There was no argument. There was
> >> a blanket pronouncement that _in mathematics_ mod is not a binary
> >> operator. I should learn to challenge such pronouncements and ask what
> >> the problem is. Maybe next time.
>
> > So this was *one* person making that claim?
>
> > I understand that, in general, mathematicians don't have much need for a
> > remainder function in the same way programmers do -- modulo arithmetic is
> > far more important. But there's a world of difference between saying "In
> > mathematics, extracting the remainder is not important enough to be given
> > a special symbol and treated as an operator" and saying "remainder is not
> > a binary operator". The first is reasonable; the second is not.
>
> The professional mathematicians that I know personally don't say that "remainder
> is not a binary operator". They *do* say that "modulo is not an operator" in
> mathematics just because they have reserved that word and the corresponding
> notation to define the congruence relations. So for example, the following two
> statements are equivalent:
>
>    42 = 2 mod 5
>    2 = 42 mod 5
>
> The "mod 5" notation modifies the entire equation (or perhaps the = sign if you
> like to think about it like that), not the term it is immediately next to.
> Python's % operator is a binary operator that binds to a particular term, not
> the whole equation. The following two are not equivalent statements:
>
>    42 == 2 % 5
>    2 == 42 % 5
>
> It's mostly kvetching on their part that programming language designers
> misunderstood the notation and applied the name to something that is confusingly
> almost, but not quite, the same thing. They aren't saying that you couldn't
> *define* such an operator; they would just prefer that we didn't abuse the name.
> But really, it's their fault for using notation that looks like an operator.
>
> --
> Robert Kern
>
> "I have come to believe that the whole world is an enigma, a harmless enigma
>   that is made terrible by our own mad attempt to interpret it as though it had
>   an underlying truth."
>    -- Umberto Eco

Thanks Robert, I think you cut right through the confusion there.

To tie it back in with python language design; all the more reason not
to opt for pseudo-backwards compatibility. If python wants a remainder
function, call it 'remainder'. Not 'rem', not 'mod', and certainly not
'%'. Its the more pythonic way; a self-describing name, rather than
poorly defined or poorly understood cryptology.