CODEWITHSUNDEEP
fortran
user3716774
user3716774

Reputation: 441

Is it possible to write a function with dynamic input in Fortran?

I am new to fortran, and am wondering whether it is possible to write a function or subroutine with dynamic input? For example, if I want a function/subroutine :

function/subroutine a (inputs)

  integer, dimension(:), allocatable :: b
  integer :: i,j

  i = number of inputs
  allocate(b(i))

  do j=1,i
    b(i)=input(i)
  end do

end function a

So the number of inputs can be different every time I call the function/subroutine. Is it possible?

Upvotes: 0

Views: 619

Answers (1)

Vladimir F Героям слава
Vladimir F Героям слава

Reputation: 60113

When all the arguments are of the same type, you can pass them in an array:

subroutine a(inputs)
    integer :: inputs(:)
    integer,  allocatable :: b(:)
    integer :: i,j

    i = size(inputs)
    allocate(b(i))

    do j=1,i
      b(i)=input(i)
    end do

If they are of different types you can use optional dummy arguments. You must check every argument if it is present before accessing it.

subroutine a(in1, in2, in3)
    integer :: in1
    real :: in2
    character :: in3

    if (present(in1)) process in1
    if (present(in2)) process in2
    if (present(in3)) process in3

You can also use generics, where you manually specify all possible combinations and the compiler then selects the right specific procedure to call. See your favorite textbook or tutorial for more

module m

  interface a
    module procedure a1
    module procedure a1
    module procedure a1
  end interface

contains

   subroutine a1(in1)
     do something with in1
   end subroutine

   subroutine a2(in1, in2)
     do something with in1 and in2
   end subroutine

   subroutine a2(in1, in2, in3)
     do something with in1, in2 and i3
   end subroutine

end module

...
use m
call a(x, y)

Upvotes: 3

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