! This file:
! http://ftp.aset.psu.edu/pub/ger/fortran/hdk/OptionalArgs.f90
!
!  Example of using F90 Optional Arguments
!
 module demo
   implicit none
   contains  !  An explicit Interface is required.
     subroutine anysub(intarg1, outarg, intarg2)
       integer :: intarg1, intarg2
       real :: outarg
       intent(in) :: intarg1, intarg2
       intent(out) :: outarg
       optional :: outarg, intarg2

     print *, " "
     print *, "intarg1=",intarg1
     if (present(outarg)) then
       outarg=intarg1*10
       print *, "outarg=",outarg
     endif
     if (present(intarg2)) then
       print *, "intarg2=",intarg2
     endif
   end subroutine anysub
 end module demo

program main
   use demo
   intarg1=1
   call anysub(intarg1, outarg, 2)
   call anysub(intarg1, outarg)
   call anysub(intarg1, intarg2=3)
   call anysub(intarg1)
end program main

! Results:
! intarg1= 1
! outarg= 10.0000000
!intarg2= 2

!intarg1= 1
!outarg= 10.0000000

!intarg1= 1
!intarg2= 3

!intarg1= 1