SUCC returns a floating-point value that is the smallest representable
number larger than x. It is the base, mode, and precision
of x. The OVERFLOW condition is raised if there is no such
number.
>>-SUCC(x)-----------------------------------------------------><
- x
- REAL FLOAT expression.
SUCC satisfies the following relationships:
pred(succ(x)) = x
succ(pred(x)) = x
succ(x) = -pred(-x)
succ(0d0) = tiny(0d0)