From: Brian Mitchell <binary42@...>
Date: 2006-10-06T23:46:59+09:00
Subject: Re: Compound Parallel Operators

On 10/6/06, Carlos <angus@quovadis.com.ar> wrote:
> Phrogz wrote:
> [...]
> > Now, I would consider it a valid argument to say "Let's not codify a
> > particular interpetation of some syntax that conflicts with another
> > reasonable interpretation, because it will be surprising to a notable
> > percentage of programmers." Would anyone say that they personally have
> > a different expectation for what "a,b += x,y" might mean?
>
> "The same as
>    a,b = a,b + x,y
>   but with a,b evaluated only once"?

An example of how we already have behavior that most don't realize:

var = :red
var, var[:ruby] = {}, var

Note that this will actually work which means you have to decompose to
a much more complex structure... one with things like temp vars:

# Right
one = {}
two = var
# Left
var = one
var[:ruby] = two

Or course we could optimize that to:
# Temps
two = var
# Left
var = {}
var[:ruby] = two

... but that is about all the complexity we need. It gets ever more
confusing with parallel operators.

Now it gets confusing because the time things get referred to is all messed up:

# Not real code!

var = 'ruby'
var, var += var, var.reverse

one = var
two = var.reverse
var += one #=> ruby + ruby
var += two #=> (ruby + ruby) + ybur

Confusing enough for me. I'm not sure I would really use parallel
operators. I do use, parallel assignment quite a bit (nice for
argument handling and just avoiding temp vars in general).

With all of that said, I am not sure if I am really against the
concept either. It just isn't really important to me.

Brian.