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Isnan - checks to see if a floating point number holds a real number math unit

function IsNaN ( const Float : Single | Double | Extended ) : Boolean; Description The IsNaN function returns True if the Float parameter is Not a number. A floating point number can be set to such a value when it is assigned an undetermined value. The standard is : NAN = 0.0 / 0.0 Related commands Infinity Floating point value of infinite size IsInfinite Checks whether a floating point number is infinite NaN Not a real number Example code : Assign NAN to a number and then test using IsNaN var float : Double; begin // Set the number to an invalid number float := NAN; // Equivalent to 0.0/0.0 // Although an invalid number, we can still display it ShowMessage('float = '+FloatToStr(float)); // And we can test to see if it is a valid number if IsNaN(float) then ShowMessage('float is not a number') else ShowMessage('float = '+FloatToStr(float)); end; Show full unit code float = NAN float is not a number