Fortran Function with return type depending on parameters

Question

If you look at the definition of the intrinsic function CEILING it has an optional parameter KIND which can be used to force the return value's integer kind.

Would there be any way to implement my own function in Fortran in such a way as to have the kind, or even better the type of the returned value of a function depend on a parameter? I've tried something like this:

program test_kind
    use iso_fortran_env
    implicit none
    integer(kind=int32) :: a
    print*, kind(a)
    print*, kind(kt(int16))
    print*, kind(kt(int32))
contains
    function kt(kind)
        implicit none
        integer, intent(in) :: kind
        integer(kind=kind) :: kt
        kt = 100
    end function kt
end program test_kind

But it fails with the error:

test_kind.f90:12:21:

         integer(kind=kind) :: kt
                     1
Error: Parameter ‘kind’ at (1) has not been declared or is a variable, 
which does not reduce to a constant expression

Now I know I can use procedure overloading to have the same name associated with different procedures depending on the types of arguments. But I'm asking whether the type of the return value can depend on the value of an argument.

Answer 1

No. It is not possible in the standard language, as of F2015 draft. The intrinsic procedures are special in this regard.

Dummy arguments that are data objects are always variables in non-intrinsic procedures.

Kind parameters must be given by constant expressions, and variables are not constants. The rules for nominating the type of an object in a scope are practically more restrictive.