[Python-ideas] PEP 505: None-aware operators

[Amit Green]

On Thu, Jul 26, 2018 at 1:09 AM, Steven D'Aprano <steve at pearwood.info>
wrote:

> On Thu, Jul 26, 2018 at 01:02:47AM -0400, Amit Green wrote:
>
> > 3.  The problem is way deeper than simply adding '?.' and other
> operators.
> > For real use cases, you also need to say "how far" the an operator can
> > "spread" -- and this is real hard to solve.
>
> Why do you think that is the case? No other operators "spread". Why
> should these?
>

If you take 'a?.b.c' then if the first '?.' yields none, logically you
don't want to evaluate the second '.'; otherwise you have to write:

a?.b?.c -- And this starts to look like line noise.

If you also implemented a concept such as use non-aware operators in
function calls: such as:

f(a, b?, c) -- which would mean collapse the whole thing out of
non-existance if 'b' yields none (i.e.: don't call function f) -- how far
does this spread?  Outside of f, if you then write:

f(a, b?, c).d.e

Does this also mean don't evaluate the '.d' & '.e' ?

And both of these examples are from *REAL* uses cases in my code I would
want to use none-aware operators.


>
> > 4.  Coming up with a readable syntax that doesn't look like line noise is
> > really hard; and very subjective.
>
> Define "line noise".
>
> Is a.b.c syntax line noise?
>
> Is a**b**c syntax line noise?
>
> Is a == b == c line noise?
>
>
>
These examples, from python, all look great & are very readable.  Which is
why python is such a great language :)

Simple non-aware operators are also very readable, such as: a?.b

This starts to become unreadable & line noise: a?.b.c.d ?? "hi".

Again, though it is subjective -- as is clearly evident by the discussions
in this group.

My simple point above is -- I really do want this feature -- but having
tried for days, I can't come up with a really clean syntax to capture all
of my *OWN* use cases ... let alone others...

Anyway, as I said, I think we have more important issues to address right
now, than this very difficult issue & I'll write up more tomorrow.
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