From: "Hal E. Fulton" <hal9000@...>
Date: 2003-06-04T04:29:31+09:00
Subject: Re: case of sub! not working

----- Original Message ----- 
From: "Michael Campbell" <michael_s_campbell@yahoo.com>
To: "ruby-talk ML" <ruby-talk@ruby-lang.org>
Sent: Tuesday, June 03, 2003 8:15 AM
Subject: Re: case of sub! not working


> 
> > Thanks for the explanation. This definitely violates the principle
> > of
> > least surprise, however, and I consider it a bug. At the very
> > least, it
> > should go into the documentation, including the FAQ.
> 
> Can someone mention *why* this is like it is?  (ENV keys are copies
> so modifications are lost.)

I'll take a stab at it. I can't promise that
what I say is correct.

The illusion of ENV being a simple hash is a 
good one. But remember that when you get/set
environment variables, ultimately you are 
calling getenv/setenv or some equivalent.

It's one thing to do an ENV[x] = y, as []=
is a method invoked on ENV. We can trap the
change and call setenv.

But if ENV[x] refers to a string, and I change
that string... then ENV itself hasn't changed.
In fact, for an in-place change, even the 
object id of the string hasn't changed.

To accomplish something like ENV[x].sub! working
intuitively, we would have to monitor every 
string object referenced by ENV and watch to see
when any of them was changed.

Perhaps possible but impractical and inefficient.

Hal