Fortran: Can a procedure, contained in a module, call another procedure contained in the same module? [closed]

Question

For instance, consider a module with the following general structure:

module test
    implicit none

    contains 

    function f(x)
    ...
    end function f


    subroutine sub()
    ...
        y = f(x)
    ...   
    end subroutine


end module test

As such this is incorrect, as is doing something similar inside a program (internal procedures can not reference each other). When I tested it in an module, I still get the same error. Presently I am putting f outside the module, and it works. The reason I am not satisfied with that is I want f to be available to programs that use test; now it is available only to the procedures that are defined inside this module file.

Answer 1

Put two print, *s in that code and test it yourself. That's a very simple question to test.

Answer 2

There is nothing wrong with your module. And yes, you can certainly call a module procedure from inside another module procedure. This is one of the major reasons for the existence of modules in Fortran since the 1980s: to encapsulate all relevant procedures in one programming unit. But keep in mind that you do not need to use a module procedure to call it in another module procedure. The interfaces of all module procedures are exposed to each other. So this would be wrong:

module test

    implicit none

contains 

    function f(x)
    end function f

    subroutine sub()
        use test, only: f ! This is wrong and there is no need for it
        y = f(x)
    end subroutine

end module test

If you had a minimal working example of your problem that could have helped significantly better pin down the cause of the error. I suspect this error is not about what you think it is as it is totally possible in Fortran.