From: Jeremy Kemper <jeremy@...>
Date: 2005-11-18T05:04:30+09:00
Subject: Re: Object#to_b

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On Nov 17, 2005, at 6:49 AM, mental@rydia.net wrote:
> Quoting Jeremy Kemper <jeremy@bitsweat.net>:
>
>> I would not like new false values, but I would like to be able to
>> proxy the existing false values.  Especially nil.
>
> Ah, fudge.  I hadn't thought of that.  That is one place where
> lazy.rb falls down.
>
> promise { false } will always be true :/
>
> (unless you use an explicitly force()'d value.)
>
>> What is the cost [of allowing NilClass and FalseClass subclasses]?
>
> I don't see any way that it could be as efficient as the current
> setup, where nil and false are immediate values and are checked
> with a simple bitmask.

Right: I had to dig as far as RTEST when I tried to act like nil
to understand why it did not work.  I was happy to see that it's
very fast but was unhappy to discover the "line in the sand" between
dynamic, expressive Ruby and its concern for raw performance.

There is a Moore's law for one but not the other.

Has anyone measured the cost of doing boolean tests the Ruby way?
Clearly it will be much slower as a microbenchmark, but perhaps the
overall cost for most Ruby programs is low enough to tip the balance.

And if not now, perhaps in one year.

jeremy
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