! exf6.f90   define and use functions and subroutines

module functions    ! inside here, usually compiled as a separate file
  public :: fun
  contains
  function func(t) result (r)
    real, intent(in) :: t   ! declare parameter types
    real  :: r              ! declare result type
    r = t + 1.0             ! last value stored in result is returned
  end function func

  subroutine subr(A)
    real, dimension(:), intent (in out) :: A  ! declare parameter type
    integer :: n
    n = size(A)
    do i = 1,n
      A(i) = A(i) + 1.0
    end do
  end subroutine subr
end module functions

program exf6
  use functions  ! makes available  func  and  subr
  
  real, dimension(1:5) :: a = (/ 1.0, 2.0, 3.0, 4.0, 5.0 /)
  real :: x = 1.0
  real :: y

  print *, "exf6.f90  define and use functions and subroutines"
  
  y = func(x)
  print *, "y=funct(x)=", y
  call subr(a)
  print *, "call subr(a) a=", a

end program exf6