From: Ca Josephson <cjosephson@...>
Date: 2009-08-10T23:28:38+09:00
Subject: Newbie has trouble understanding a Why example

I'm just learning ruby, so I am working my way through 'Why's Poignant
Guide to Ruby'

I'm on the 5th chapter, and I came across this example:

class ArrayMine < Array
   # Build a string from this array, formatting each entry
   # then joining them together.
   def join( sep = $,, format = "%s" )
     collect do |item|
       sprintf( format, item )
     end.join( sep )
   end
 end

An example of the method in action:

 rooms = ArrayMine[3, 4, 6]
 print "We have " + rooms.join( ", ", "%d bed" ) + " rooms available."

Which prints, “We have 3 bed, 4 bed, 6 bed rooms available.”

I'm confused by the line "def join( sep = $,, format = "%s" )". What on
earth is going on with the parameters? What do the  sep = $, and format
= "%s" do? If I modify that line to "def join( sep, format)", the same
thing prints out. So why are $, and %s used? What do they do?
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