Fortran Interface

[tmp]» cat test.f90                                   (evan@aeroevan:~/src/tmp)
program test
  use test_mod, only: func
  implicit none
  real :: a
  integer :: b

  a = func(1.0, 2.0)
  print *, a

  b = func(1, 2)
  print *, b
end program test

module test_mod
  interface func
    module procedure func_real, func_integer
  end interface func
contains
  function func_real(x, y) result(z)
    real, intent(in) :: x, y
    real :: z
    print *, "Calling real function"
    z = x + y
  end function func_real
  function func_integer(x, y) result(z)
    integer, intent(in) :: x, y
    integer :: z
    print *, "Calling integer function"
    z = x + y
  end function func_integer
end module test_mod
[tmp]» gfortran -o test test.f90                      (evan@aeroevan:~/src/tmp)
[tmp]» ./test                                         (evan@aeroevan:~/src/tmp)
 Calling real function
   3.0000000
 Calling integer function
           3
[tmp]»                                                (evan@aeroevan:~/src/tmp)