This function returns the “model number” that is almost negligible with respect to 1.0 for the type and kind of X.
This value is equal to REAL(RADIX(X),KIND(X))**(DIGITS(X)).
Adding EPSILON(X) to 1.0 (with the kind of X) will always produce a value greater than 1.0.
This is an inquiry function, so X need not be defined; indeed, it is permitted to be disassociated, unallocated, or absent.
The model for real type is that it may be zero or a signed fraction between 1 and 1/RADIX(X) consisting of DIGITS(X) digits, multiplied by an exponent RADIX(X)**e with MINEXPONENT(X)≤e≤MAXEXPONENT(X).
