From: Joel VanderWerf <vjoel@...>
Date: 2007-06-11T07:29:17+09:00
Subject: Re: fun with "case"

Robert Klemme wrote:
> 
> A funny (and readable) way to test collection sizes just occurred to me:
...

Some more Sunday afternoon fun...

class Cond < Proc
   alias :=== :call
end

module Kernel
   def cond
     Cond.new
   end
end

class Integer
   def elements
     cond {|enum| self == enum.size}
   end
end

class Range
   def elements
     cond {|enum| self === enum.size}
   end

   def includes_it
     cond {|enum| enum.all?{|elt| self.include?(elt)}}
   end
end

class Object
   def is_included
     cond {|enum| enum.include? self}
   end
end

require 'enumerator'
INCREASING = cond {|enum| enum.enum_for(:each_cons, 2).all?{|x,y| x < y}}

case [1,2,3]
when (3..5).elements
   puts "at least three, but no more than five, elements"
end

case [1,2,3]
when (1..4).includes_it
   puts "included in 1..4"
end

case [1,2,3]
when 2.is_included
   puts "includes 2"
end

case [1,2,3]
when INCREASING
   puts "increasing!"
end

case [1,2,3]
when 3.elements
   puts "three elements!"
when 5.elements
   puts "too much!"
else
   puts "else"
end

__END__

Output:

at least three, but no more than five, elements
included in 1..4
includes 2
increasing!
three elements!



-- 
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407