NAN  NAN Not-a-Number Constant


Usage
 
 Returns a value that represents ``not-a-number'' for both 32 and 64-bit 
 floating point values.  This constant is meant to represent the result of
 arithmetic operations whose output cannot be meaningfully defined (like 
 zero divided by zero).
 
    y = nan
 
 The returned type is a 32-bit float, but promotion to 64 bits preserves the not-a-number.  The not-a-number constant has one simple property.  In particular, any arithmetic operation with a NaN results in a NaN. These calculations run significantly slower than calculations involving finite quantities!  Make sure that you use NaNs in extreme circumstances only.  Note that NaN is not preserved under type conversion to integer types (see the examples below).
 