From: Louis J Scoras <louis.j.scoras@...>
Date: 2006-10-28T22:11:53+09:00
Subject: Re: What are closures, continuations?

On 10/28/06, Simen Edvardsen <toalett@gmail.com> wrote:

> The lambda calculus took it from the Greek Alphabet, who adapted it
> from the Phoenecian Alphabet, and so on (you could keep going
> forever). Actually closures are never called "lambdas", at least not
> in any writing I've read on Lisp, it's just a symbol used to denote a
> closure.

Right.  It's best just to think of lambda as a way to get anonymous
functions. It's more or less like Proc.new (close enough).

Closures are a property of functions, but they have much more to do
with lexical scoping.  In fact, older lisps didn't have lexical
closures because because they were dynamically scoped.  Also, there is
a mathematical property called closure that is referred to in lisp
texts which has nothing to do with lexical closures.

    x = 1
    (1..5).each {|i| i + x}

You can use the x variable because the block is a closure.  Really,
you don't think about it too much, as it just does what you would
expect.


Unless you were expecting the wrong thing =)



-- 
Lou.