From: Rick DeNatale <rick.denatale@...>
Date: 2009-08-10T23:49:50+09:00
Subject: Re: Newbie has trouble understanding a Why example

On Mon, Aug 10, 2009 at 10:28 AM, Ca Josephson<cjosephson@ebscohost.com> wrote:
> 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?

They provide default values for the parameters.

try:

print "We have " + rooms.join( ", " ) + " rooms available."
or
print "We have " + rooms.join + " rooms available."

with and without your modification.

-- 
Rick DeNatale

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