From: Florian Gross <flgr@...>
Date: 2005-02-17T08:19:50+09:00
Subject: Re: A little bit confused about array+array addition (bug or expected behavior?)

gga wrote:

> irb(main):082:0> def add(x)
> irb(main):084:1>    x += [5,6]
> irb(main):085:1> end
> 
> irb(main):087:0> add(a)
> => [1, 2, 3, 4, 5, 6]
> irb(main):088:0> a
> => [1, 2, 3, 4]        ===>>> uh?  am I not passing stuff by reference?
>  where is 5, 6?

You are not passing variables by reference, you are passing objects by 
reference.

Ruby does not have a built-in way of doing variable by reference as 
variables are usually not first-class objects. (They are names for objects.)

You probably want to do x.replace(x + [5, 6]) or x.push(5, 6) which 
modify the object itself.

This has come up frequently in the past -- if you are willing to do a 
bit of research on google groups you will find implementations of 
first-class variable objects, using lambdas for modifying variables in 
other scopes and more.