From: gwtmp01@...
Date: 2006-09-11T11:52:18+09:00
Subject: Re: Struggling with Blocks


On Sep 10, 2006, at 6:45 PM, Paul Lutus wrote:
> "do" reads from a list of items and provides them to its  
> controlling block:
>
> (implicit "do")
>
> array.each { |item|
>    # do something here
> }
>
> (explicit "do")
>
> array.each do |item|
>    # do something here
> end
>
> These two forms are interchangeable. One can argue that "do" is an  
> implicit
> "{ ... }" block, or the reverse. But the point is "do" receives  
> items and
> operates on them one at a time, then exits when its stream is empty.

This just doesn't sound right to me.  do/end and {} are part of the  
syntax of
a method call in ruby.  They aren't operators.  There is no  
requirement that
the code in a do/end or {} block be used within some sort of a looping
or iterative context.  For example:

	File.open('datafile')  do |fd|
            # do something with the open file handle: fd
         end

A do/end block is simply a snippet of code and a set of variable  
bindings that
are made available to the called method.  The called method can  
ignore the block,
call it one or more times, call it conditionally, pass it along to  
some other
method, and so on.

Gary Wright