From: not@... (Chris)
Date: 2002-04-03T05:53:52+09:00
Subject: Re: Difference between 'do' and 'begin'

On Wed, 27 Mar 2002 16:59:36 GMT, Tobias Reif <tobiasreif@pinkjuice.com>
wrote in comp.lang.ruby:

>> a + b     # expression
>> x = a + b # statement
>
>aren't both of them expressions in Ruby?

Yes.  In OO languages every code fragment either returns a value or raises
an exception.  For that reason it would be better to think of code
fragments in terms of whether or not they have an effect out of context,
which is to say, whether or not they are composed of sub-expressions that
result in a change of state of one or more of the participants.

Ultimately this can't be known unless the internals of the objects are
available for inspection, as operator overloading could cause something as
simple as (a+b) to have a side-effect other than simply returning a value.