From: why the lucky stiff <ruby-talk@...>
Date: 2002-08-21T09:46:58+09:00
Subject: Re: the power of ruby

AW (sturmpanzer@metacrawler.com) wrote:
> Wow, Doing it that way had never accured to me.
> How does that work that you can use dot notation from a bracket '}' ? 
> I keep looking at the last line and I cant seem to grasp its
> relationship, I mean, If the first set of '{}' are containing the loop
> from the '.times' method, how do the second set relate? 
> Now i'm really confused. Thank you! ;-)

The bracketed code is a Proc object and I'm just manipulating its
return value directly.  I could do this:

  n = 78.times { |i|
        do_dot( i )
      }
  n.downto( 0 ) { |i|
    do_dot( i )
  }

See, the Integer#times method returns the original Integer.  So does
Integer#downto.  Try these in IRb:

  5.times {}
      ==>5
  5.downto( 0 ) {}
      ==>5

So I can manipulate the return value by calling methods from the block.
The above code can be rewritten:

  78.times do |i|
    do_dot( i )
  end.
  downto( 0 ) do |i|
    do_dot( i )
  end

I have thought there might be a way to loop up and down through a Range
or Integer in Ruby in a single call, but I could think of how to do it
without adding a method to Integer or Range and wasting more chars than 
the above.

> Im looking for exactly what you gave. different ways to express the
> same output in Ruby. Shorter, longer, obsfucated, clear. 
> I just hope others will chime in and give some examples of their own
> style. 

Well, in that case, I'll include one that overrides Fixnum for ya:

  def do_dot( i )
    puts "#{' ' * i}*"
  end
  class Fixnum
    def up_and_down( &p )
      times( &p ); downto( 0, &p )
    end
  end
  while 78.up_and_down { |i| do_dot( i ) }; end

Good luck.

_why