Interpolate_cubic1DF (real, intent (in) :: a (1:4), real, intent (in) :: x)
Calculates the function value for a single [x] rescaled [0,1] coordinate and the 4 monocubic expansion coefficients. The monocubic expansion reads, for one line, in terms of the rescaled [0,1] x coordinate: 3 i F (x) = sum a (i) x i=0 The location index of the a (i) inside the 4-dimensional vector is: location index of a (i) = 1 + i
a (i) : the i-th monocubic expansion coefficient x : rescaled [0,1] x coordinate
1) The code checks, if the supplied coordinate [x] is rescaled.