From: Michael Edgar <adgar@...>
Date: 2011-08-05T02:50:51+09:00
Subject: Re: multiple array declaration using one Object::new call

--Apple-Mail=_D92D5D85-AE33-47EC-BC5A-55A7FA49C829
Content-Transfer-Encoding: quoted-printable
Content-Type: text/plain;
	charset=us-ascii

On Aug 4, 2011, at 1:42 PM, Andy Davis wrote:

> Hello,
>=20
> I apologize if this has been covered, but I searched and could not =
find
> anything resembling this issue.  I am fairly new to Ruby and I'm =
having
> a strange problem that may be my misunderstanding of how Ruby works.
>=20
> I am trying to declare multiple arrays on one line, like such:
>=20
> array1, array2, array =3D Array::new()
>=20
> What happens is that the arrays are all nil and [seemingly] immutable.

This is a part of ruby that can trip us all up at times. What you're =
seeing
here is implicit array expansion on the right-hand side. It's easiest to
illustrate with a motivating example:

a, b, c =3D [1, 2, 3]

On the left-hand side, we have 3 variables, and on the right-hand side, =
we
have 1 value. The value on the right is an Array, so it is expanded into =
the
equivalent:

a, b, c =3D 1, 2, 3

If the array isn't big enough to satisfy all the left-hand side =
variables, it puts
"nil" in the expanded assignment:

a, b, c =3D [1, 2]

becomes

a, b, c =3D 1, 2, nil

What you've got is equivalent to this:

a, b, c =3D [ ]

which becomes:

a, b, c =3D nil, nil, nil

by the same rule as above.

For a more precisely-worded explanation of all this, see "Read Ruby", a
nice online manual for Ruby 1.9: =
http://ruby.runpaint.org/variables#assignment

Michael Edgar
adgar@carboni.ca
http://carboni.ca/


--Apple-Mail=_D92D5D85-AE33-47EC-BC5A-55A7FA49C829--