From: Curt Sampson <cjs@...>
Date: 2008-02-09T15:53:47+09:00
Subject: Re: info on block arguments

On 2008-02-09 13:22 +0900 (Sat), Russell Me wrote:

> 3.times {|x| puts x }
> 
> I see it work, I understand what's going on, but I don't know HOW it's 
> working.

The key point you may be missing is that, unlike blocks in C, a block in
ruby is a code definition; it defines a function. This function is an
object, like any other, and so you can store it, call it later, etc. So:

    f = proc { |x| puts(x * 2) }

prints nothing but, f now points to an object representing that
function. (The "proc" is just an artifact of some inconsistent language
design; you don't need it when a function comes before the block
definition.)

So try calling it:

    f.call(0)			# prints "0"
    f.call(1)			# prints "2"
    f.call(2)			# prints "4"

Now, some functions can take a block and call it multiple times..

    3.times(&f)			# prints "0", "2", and "4", just as above

Next step: get yourself a copy of _The Little Schemer_ and work through
it. Then you will achieve much better understanding of many programming
languages, including Ruby.

cjs
-- 
Curt Sampson       <cjs@starling-software.com>        +81 90 7737 2974   
Mobile sites and software consulting: http://www.starling-software.com