I am writing some code which involves numerical integration of a function on a 3D grid of points. I am defining the type vector to refer to these points, and I am also trying to extend the intrinsic operator * to include scalar and vector multiplication. However, I cannot compile and I don't know how to fix it. I am having trouble with and without the module, but I think it would be better to make it work as a module. I am not sure how to go about getting this to work, though. This one includes just scalar multiplication: module modvec type vector real, dimension(3) :: x end type vector interface operator(*) module procedure distributive end interface contains function distributive(a,v) result (w) real, intent(in) :: a type(vector), intent(in) :: v type(vector), intent(out) :: w do i=1,3 w(i) = a*v(i) enddo end function distributive end module modvec This does not compile in the main or as a module. What am I doing wrong?