11.差分演算子の定義


interface d_x
 module procedure d_x1d, d_x2d, d_x3d !多重定義
end interface

function d_x1d(input) result(output)
 type(var1d), intent(in) :: input !引数が１次元ならこれが呼ばれる type(var1d) :: output

 nullify(output%value)
 output%value =>  my_allocate_1d()
 output%grid(1) = mod( input%grid(1) + 1, 2 )
 output%value(lb_axis1+output%grid(1):ub_axis1-1+output%grid(1)) & 
 = ( input%value(lb_axis1+1:ub_axis1) &
   - input%value(lb_axis1:ub_axis1-1) ) / dx

end function d_x1d