"rcoder" <rcoder / gmail.com> wrote in message 
news:1121809476.588549.318170 / g47g2000cwa.googlegroups.com...
> This isn't specific to IRb -- any time you reload code which defines
> constants, (variables with names that begin with a capital letter, such
> as 'MY_VARIABLE' or 'MyConstant') the Ruby runtime will throw a warning
> about the constant being redefined.
>
> You can see this behavior in its simplest form with code like the
> following:
>
> --- begin 'const_warn_demo.rb' ---
>
> # set a constant
> FOO = 'bar'
>
> # do something...
>
> # now, set the constant again
> FOO = 'baz'
>
> --- end ---
>
> Constants are designed to be read-only values, so a warning when
> they're re-assigned is appropriate.
>
> -Lennon
>
>
Lennon.

Thanks for your reply!
I understand your answer to part one of my question, do you have anything to 
say about part two? I.e. can an IRB session be reset to an uninitialized 
state? In other words, is there a way to do an "unload?" or the 
equivalent???  A related question might be: can one undefine a constant, 
(like one can undef a methiod)?