fungibility.rb

FUNGIBLE = [:coin, :coin, :coin, :coin]
INFUNGIBLE = [:coin, :cow, :wine, :kebab]
# Is each unit in the list of assets interchangeable?
def fungible?(assets)
  if assets.all?{ |unit| assets.all? {|other_unit| unit==other_unit }}
    puts "#{assets.inspect} is fungible"
  else
    puts "#{assets.inspect} is not fungible"
  end
end

fungible?(FUNGIBLE) 
# [:coin, :coin, :coin, :coin] is fungible

fungible?(INFUNGIBLE)
# [:coin, :cow, :wine, :kebab] is not fungible