So what does (inout int = 0) do?

[Guillaume Piolat via Digitalmars-d]

On Friday, 15 April 2016 at 05:38:56 UTC, Andrei Alexandrescu 
wrote:
>
> I think we should deprecate inout. For real. It costs way too 
> much for what it does. For all I can tell most of D's 
> proponents don't know how it works. -- Andrei

This is the explanation I came up with, not sure if accurate. And 
only to teach myself the basics.
https://p0nce.github.io/d-idioms/#Knowing-inout-inside-out

I'm all for removing things!