From: Brian Candler <b.candler@...>
Date: 2008-12-02T22:52:17+09:00
Subject: Re: Adventures in Optimization... or why CONST frozen is Good

> Now I have a class CONSTANT...
>    UNDEFINED = 'U'.freeze
> 
> and
>    symbols_needed[symbol_name] = UNDEFINED

Yes, that's the "right" solution with Ruby today, and you'll see this 
done in a lot of Ruby libraries. (Perhaps it would be nice if there were 
some syntax to define an inline frozen string literal)

I don't consider this any sort of "optimisation" though. It's 
fundamental to the nature of Ruby that there is only one kind of value, 
which is a reference to an object. An assignment always copies only the 
reference.

This is a breath of fresh air when compared to, say, Perl. Is this value 
a scalar? Is it a scalar number or string, or a reference to an Array or 
a Hash, or a typeglob, or a filehandle, or ...?

However, you could argue that string literals should have been immutable 
(like Symbol). The language would end up being somewhat different to 
use:

    a = "hello"           # maybe Symbol or StringLiteral
    b = String.new(a)     # mutable String
    b << " world"

You'd also have to have a load of rules to work out. Should a.dup return 
the same Symbol, or a new mutable String? Should (a + "world") return a 
new Symbol, or a new mutable String?

From this point of view, just having String keeps things simple, even if 
it does end up creating a load of garbage objects. In those cases where 
this matters, your approach (of profiling and zapping) is a good one.
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