NaN, standing for not a number, is a numeric data type value representing an undefined or unrepresentable value, especially in floating-point calculations.
In floating-point calculations, NaN is not the same as infinity, although both are typically handled as special cases in floating-point representations of real numbers as well as in floating-point operations.
 NaNs can support advanced features such as mixing numerical and symbolic computation or other extensions to basic floating-point arithmetic.

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