What is the best way to "combine" two Fortran subroutines with very similar functionalities but slight differences?

Question

I have two modules with an init subroutine that look as following:

module letter_A
contains  
subroutine a_init()
  *do something*
  call my_function(1)
  print *, "letter A init"
end module letter_A

module letter_B
contains  
subroutine b_init()
  *do something*
  call my_function(2)
  print *, "letter B init"
end module letter_B

I would like to create a supermodule and convert the modules A and B to submodules, and outsource as much functionality as possible to the supermodule to reduce the amount of redundant code in my application. Currently, the only way I can think of how to do this is as following:

module letter
contains  
subroutine letter_init()
  *do something*
#if defined(A)
  a_init(1)
#elif defined(B)
  b_init(2)
#endif
end module letter

submodule(letter) A
contains  
subroutine a_init()
  call my_function(1)
  print *, "letter A init"
end module letter_A

...

However, this only works for this particular minimal example. If I have more function calls with more identical *do something* blocks inbetween, it becomes harder to separate the redundant parts in a seperate module and it's also not very nice to have to pass 10+ values to an init function. Is there a more sophisticated way of solving this problem?

Answer 1

Maybe I am missing something important (?), but the answer to your question looks as simple as that to me:

subroutine letter_init(letter)
  character(1), intent(in) :: letter
  !*do something*
  if (letter == 'A') then
     call my_function(1)
  else if (letter == 'B') then
     call my_function(2)
  end if
  print *, "letter "//letter//" init"
end subroutine letter_init