From: Alex Young <alex@...>
Date: 2007-01-29T19:09:35+09:00
Subject: Re: Flow of execution

Mark Woodward wrote:
> Hi all,
> 
> Could someone explain the 'flow' of how the eg below is processed?
> My limited understanding is that the left hand side is the receiver and
> the right hand side the method being passed to the receiver?
> 
> What I don't understand is where the block comes into the equation for
> something like the following:
> 
> values = anagrams.values.sort do |a, b|
>   b.length <=> a.length
> end
> 
> 
> The block changes how the sort method sorts? ie it sorts by length rather
> than alphabetically? So it overrides the default meaning of <=>??
> 
> We get the values of the anagram hash by the 'values' method? 
> We then do:
> 
> .sort do |a, b| b.length <=> a.length end
> 
> ie this whole line acts on the values array??
> not a 2 step process of 1. the sort method then 2. the block applied in
> some way?
> 
> To illustrate what I'm failing dismally to explain here:
> Using () for grouping, is it processed as A or B?
> 
> A
> values = anagrams.values.(sort do |a, b|  b.length <=> a.length)
> end
This, almost.  It's more like:

values = anagrams.values.sort(do |a,b| b.length <=> a.length end)

The block essentially acts as a parameter to the sort method.  The sort 
method uses the result of passing each pair to the block to perform the 
actual sorting.

-- 
Alex