Check if number is NaN

Question

I'm trying to check if a variable I have is equals to NaN in my Ruby on Rails application.

I saw this answer, but it's not really useful because in my code I want to return 0 if the variable is NaN and the value otherwise:

 return (average.nan ? 0 : average.round(1))

The problem is that if the number is not a NaN I get this error:

NoMethodError: undefined method `nan?' for 10:Fixnum

I can't check if the number is a Float instance because it is in both cases (probably, I'm calculating an average). What can I do? It is strange only to me that a function to check if a variable is equals to NaN is avaible only to NaN objects?

Answer 1

I found this answer while duckducking for something that is not either NaN or Infinity (e.g., something that is a finite number). Hence I'll add my discovery here for next googlers.

And as always in ruby, the answer was just to type my expectation while searching in the Float documentation, and find finite?

n = 1/0.0 #=> Infinity
n.nan? #=> false
n.finite? #=> false

Answer 2

The best way to avoid this kind of problem is to rely on the fact that a NaN isn't even equal to itself:

a = 0.0/0.0
a != a
# -> True !

This is likely not going to be an issue with any other type.