From: Just Another Victim of the Ambient Morality <ihatespam@...>
Date: 2006-08-02T08:55:06+09:00
Subject: Re: I thought this was the one that worked?


"Jacob Fugal" <lukfugl@gmail.com> wrote in message 
news:507567670608011256r43f08bd5w3f5a43b00d80df32@mail.gmail.com...
>
>  # 3) block yielded to
>  def baz
>    yield "world"
>  end
>
> David's point, however, is that in the third example, when yield is
> used instead of converting it to a block, the code inside the block
> never really leaves the context in which it is created, because of the
> way non-converted blocks are implemented. More specifically, that
> implementation doesn't need to store that environment. This is a
> probable reason for the speed difference between converted blocks
> (first class procs) and unconverted blocks (yield). Since the
> environment is never stored, it's not really a closure *in the
> implementation*. This is the hair that David was splitting.

    Maybe you know more about the implementation of blocks than I do but I 
find it hard to believe that yielded blocks don't store a reference to their 
environment.  I mean, they were able to access it, right?  How does it do 
that without that reference?


> But semantically, whether a block is converted to a proc or just
> yielded to, the behavior regarding variable scope is identical; so if
> one is a closure, it's useful to refer to the other as a closure as
> well, even if it's not implemented as a true closure. In this sense,
> all blocks are closures.

    I believe that, when describing a programming language and its features, 
the behaviour of the language is more important than its implementation.  I 
mean, the language is defined by its specification rather than some 
implementation, right?