RRSPACING — Reciprocal of the relative spacing ¶RRSPACING(X) returns the  reciprocal of the relative spacing of
model numbers near X.
Fortran 90 and later
Elemental function
RESULT = RRSPACING(X)
| X | Shall be of type REAL. | 
The return value is of the same type and kind as X.
The value returned is equal to
ABS(FRACTION(X)) * FLOAT(RADIX(X))**DIGITS(X).
SPACING — Smallest distance between two numbers of a given type