From: James Edward Gray II <james@...>
Date: 2007-01-01T05:05:17+09:00
Subject: Mini-RCR:  Extra Argument for Array#join

I've been looking at the to_sentence() method in Rails.  It's  
basically a join(), but you can give a different final separator.  I  
personally use this kind of functionality often enough to believe it  
would make a good addition to the core language.

Even better, I think we can make join() smart enough to eliminate any  
need for to_sentence() by adding a second argument.  Here's a sample  
implementation:

#!/usr/bin/env ruby -w

require "enumerator"

class Array
   alias_method :old_join, :join
   def join(sep = $,, last_sep = sep)
     return "" if empty?
     enum_with_index.inject("") do |str, (e, i)|
       "#{str}#{i == size - 1 ? last_sep : sep}#{e}"
     end[sep.to_s.length..-1]
   end
end

if __FILE__ == $PROGRAM_NAME
   require "test/unit"

   class TestJoin < Test::Unit::TestCase
     def test_old_matches_new
       assert_equal([].old_join,          [].join)
       assert_equal([1].old_join,         [1].join)
       assert_equal([1, 2].old_join,      [1, 2].join)
       assert_equal((1..5).to_a.old_join, (1..5).to_a.join)

       assert_equal([].old_join("|"),          [].join("|"))
       assert_equal([1].old_join("|"),         [1].join("|"))
       assert_equal([1, 2].old_join("|"),      [1, 2].join("|"))
       assert_equal((1..5).to_a.old_join("|"), (1..5).to_a.join("|"))
     end

     def test_new_last_arg_behavior
       assert_equal("1, 2, 3, 4, and 5", (1..5).to_a.join(", ", ",  
and "))
       assert_equal("1, 2, 3, 4 and 5",  (1..5).to_a.join(", ", " and  
"))
       assert_equal("1, 2, 3, 4 & 5",    (1..5).to_a.join(", ", " & "))

       assert_equal([1, 2].join(","), [1, 2].join("ignored", ","))
     end
   end
end

__END__

Does anyone else like this?

James Edward Gray II