Ruby/Number/nan

num = 4 # => 4
if num.integer?
  puts "Invited guests: " + num.to_s
else
  puts "Only whole persons can come to this party."
end

val = 0.0/0.0
val.inspect # => "NaN"

12.integer? # => true
12.0.integer? # => false
-1.integer? # => true
-12.integer? # => true

val = 1.0
val.nan? # => false

nan = 0.0/0.0;     # zero divided by zero is not-a-number
nan < 0            # false: it is not less than zero
nan > 0            # false: it is not greater than zero
nan == 0           # false: it is not equal to zero
nan == nan         # false: it is not even equal to itself!
nan.equal?(nan)    # this is true, of course