⁶Note the declaration of the arrays Y, YP: real(8) :: Y(*),YP(*). These arrays are “assumed-size” arrays for the functions F, energy, i.e. arrays whose size is unknown to the procedure. For arrays of more than one dimension, only the last index is allowed to be *. In general it is recommended that assumed-size arrays be avoided and declare them as assumed-shape like in the program rkA.f90 of page 738. The declaration in this case is real(8) :: Y(:),YP(:)