From: Gavin Sinclair <gsinclair@...>
Date: 2002-08-16T13:39:43+09:00
Subject: Re: Hello everyone!


> I'm just learning ruby and so far everything has been great (using the
> Thomas and Hunt book), but I don't quite understand how proc objects
> (and its call method) relate to code blocks. If anyone could explain I
> would greatly appriciate it.


It's reasonably simple.  The following code snippets are equivalent:

+++++++++++++++++++++++

array.each do |e|
  puts "Data: #{e}"
end

=====================

block = proc { |e| puts "Data: #{e}" }
array.each(&block)

+++++++++++++++++++++++


From the method's side, these are equivalent:

(e.g.
  count(5..15) { |i| i % 4 == 0 }   ==> 2
  p = proc { |i| i % 4 == 0 }
  count(5..15, &p)                  ==> 2
)

+++++++++++++++++++++++

def count(range)
  result = 0
  for i in range
    result += 1 if yield i
  end
  result
end

=====================

def count(range, &block)
  result = 0
  for i in range
    result += 1 if block.call(i)       # or block[i]
  end
  result
end

+++++++++++++++++++++++


Let the corrections flow in!

Cheers,
Gavin