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Concepts - Not a Number (NaN)

<cat>Dev.Lua</cat>
<title>Concepts - Not a Number (NaN)</title>
# Not a Number (NaN)

Not a Number (NaN) is a special value returned as the result of math operations that are logically or mathematically invalid.  
One of the more common ways to create a NaN value is to divide zero by zero.  


<example>
	<description>
NaN has some qualities that may not be immediately obvious, but are important to know:
	</description>
	<code>
-- Intentionally create a NaN value for testing
local NaN = 0/0

-- It is not self-similar
-- This is the main way that NaN values are detected in lua
-- Prints: false
print( "Is NaN self-similar?", NaN == NaN )

-- It isn't nil
-- Prints: false
print( "Is NaN nil?", NaN == nil )

-- It's not positive
-- Prints: false
print( "Is NaN positive?", NaN > 0 )

-- It's not negative
-- Prints: false
print( "Is NaN negative?", NaN < 0 )

-- It's not zero
-- Prints: false
print( "Is NaN zero?", NaN == 0 )

-- It's not true
-- Prints: false
print( "Is NaN true?", NaN == true )

-- It's not false
-- Prints: false
print( "Is NaN false?", NaN == false )

-- It's truthy
-- Prints: NaN is truthy
if NaN then
  print( "Is NaN truthy?", true )
end

-- Despite the name, it is a number
-- Prints: true
print( "Is NaN a number?", type( NaN ) == "number" )
	</code>
</example>

## Additional Info

The NaN value originates from the [Floating-Point Number (float)](https://en.wikipedia.org/wiki/Single-precision_floating-point_format) standard used almost universally by software and hardware for non-integer numbers.

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