liberal_sort_by.rb

#!/usr/bin/env ruby
# liberal_sort_by.rb

class Array
  def liberal_sort
    liberal_sort_by { |x| x } 
  end 
  def liberal_sort_by(&block)
    pertains, others = partition(&block)
    pertains.sort_by(&block) + others
  end 
end

if (__FILE__ == $0) 
  
  require "rubygems"
  require "spec"
  
  LIST = [0, 1, 2, nil]
  SORT_CRITERION = lambda { |x| x    }   
  RAND_CRITERION = lambda { |x| rand }
  
  describe Array do

    describe "liberal_sort" do
      it "should sort a reversed list, putting nil comparisons at the end" do
        LIST.reverse.liberal_sort.should == LIST
      end 
      it "should sort a shuffled list, putting nil comparisons at the end" do
        shuffled_list = LIST.sort_by(&RAND_CRITERION)
        shuffled_list.liberal_sort.should == LIST
      end 
    end 
    
    describe "liberal_sort_by with criterion { |x| x }" do
      it "should sort a reversed list, putting nil comparisons at the end" do
        LIST.reverse.liberal_sort_by(&SORT_CRITERION).should == LIST
      end 
      it "should sort a shuffled list, putting nil comparisons at the end" do
        shuffled_list = LIST.sort_by(&RAND_CRITERION)
        shuffled_list.liberal_sort_by(&SORT_CRITERION).should == LIST
      end 
    end 

  end

end