# 
## Overview
A **float** value may be an invalid #key# IEEE: The Institute of Electrical and Electronics Engineers #key# floating-point number. This can be confirmed or denied by invoking the **`nan?` method** on that particular float value.

## Syntax
```ruby
float_value.nan?
```
## Parameters
**`float_value`**: This is the float value that we check to see whether it is a `NaN` or not.

## Return value
The value returned is a boolean. Therefore, it takes one of the following two values: 

- `True`: This value is returned if the `float_value` is actually a `NaN`. 

- `False`: This value is returned when the `float_value` is not a `NaN`.
## Code 


# create some float values
f1 = 2.3/0.0     # Infinity
f2 = -1.0
f3 = -9.2333/0.0 # -Infinity
f4 = 0.0/0.0

# check if NaN
puts f1.nan?
puts f2.nan?
puts f3.nan?
puts f4.nan?

## Code explanation 

* Lines 2–5: We initialize the variables `f1`, `f2`, `f3`, and `f4` with some float values.

* Lines 8–11: We invoke the `nan?` method on the variables we created, and print the results through the **`puts` method**.

How to check if a float value is not a number (NaN) in Ruby

Use the `nan?` method on a float value to determine if it's NaN, returning true or false.