case with predicates

gistfile1.rb

require 'rubygems'
require 'backports'  # aliases Proc#=== to Proc#call

rs = (0..10000).to_a.sample(30)

rs.each do |r|
  case r
  when lambda { |n| n.zero?       } then puts "#{r} is zero"
  when lambda { |n| (n % 5).zero? } then puts "#{r} is fiven"
  when lambda { |n| (n % 4).zero? } then puts "#{r} is fourven"
  when lambda { |n| (n % 3).zero? } then puts "#{r} is threeven"
  when lambda { |n| n.even?       } then puts "#{r} is even"
  when lambda { |n| n.odd?        } then puts "#{r} is odd"
  else
    raise 'unpossible'
  end
end