Check if a constant is already defined

Question

This is a simple one, I hope. How do I check, in the following example, if a constant is already defined?

#this works
var = var||1
puts var
var = var||2
put         


        

Answer 1

CONST ||= :default_value

the above works for me on ruby 1.9.3 but fails on 1.8... well 1.8 is ancient now.