[Nobu]
> Or in recent 1.7.2,
> 
>   class Temp
>     @@save = Hash.new do |h, c|
>       puts "Performing calculation...."
>       h[c] = c * 9 / 5 + 32
>     end
>     def fahrenheit(c)
>       @@save[c]
>     end
>   end

WOW! I like that!

BTW...so, if ruby was pythonish, 
"""
class Temp
    Temp.farenheit = Hash.new do |h, c|
        puts "Performing calculation...."
        h[c] = c * 9 / 5 + 32
"""
would be all the needed writing... :-)

/h