This is different to the last one:

dave[Work/rubybook 16:47:53] ruby -r prettyprint -e 
'pp=PrettyPrint.new; pp.seplist([1,2,3]){}'
/usr/lib/ruby/1.9/prettyprint.rb:191:in `seplist': undefined local 
variable or method `comma_breakable' for #<PrettyPrint:0x31354c> 
(NameError)
         from /usr/lib/ruby/1.9/prettyprint.rb:191:in `call'
         from /usr/lib/ruby/1.9/prettyprint.rb:197:in `seplist'
         from /usr/lib/ruby/1.9/prettyprint.rb:193:in `each'
         from /usr/lib/ruby/1.9/prettyprint.rb:193:in `__send__'
         from /usr/lib/ruby/1.9/prettyprint.rb:193:in `seplist'
         from -e:1

I think we need to define the method

   def comma_breakable
     breakable(", ")
   end

But I'm not 100% sure of the intended semantics


Cheers

Dave