What are the ways to pass a set of variable values through the subroutine to a function without common block?

Question

I do not want to use common blocks in my program. My main program calls a subroutine which calls a function. The function needs variables from the subroutine.

What a

Answer 1

Below is an example of how you may achieve this...

The code has been adapted from a BFGS method to show how you can pass functions and call other functions within a module...

Here I use:

• private functions nested within other subroutines
• pass variables from a subroutine to a nested function
• pass a function as an argument for a function that can be defined outside the module block

Hopefully this will cover everything for you...

Module Mod_Example

Private :: private_func

   SUBROUTINE test_routine(res,start,fin,vector,func,dfunc)
      IMPLICIT NONE
      REAL, DIMENSION(:), INTENT(IN) :: res, start, fin
      REAL, DIMENSION(:), INTENT(INOUT) :: vector

      INTERFACE
         FUNCTION func(vector)                                      
            IMPLICIT NONE                                      
            REAL, DIMENSION(:), INTENT(IN) :: vector                
            REAL :: func                                       
         END FUNCTION func                                     

         FUNCTION dfunc(vector)                                     
            IMPLICIT NONE                                      
            REAL, DIMENSION(:), INTENT(IN) :: vector               
            REAL, DIMENSION(size(vector)) :: dfunc                  
         END FUNCTION dfunc                                    
      END INTERFACE

      ! do stuff with p

      private_func(res,start,fin,vector,func,dfunc) 

      ! do stuff
   END SUBROUTINE test_routine

   SUBROUTINE private_func(res,start,fin,vector,func,dfunc)
      IMPLICIT NONE
      REAL, DIMENSION(:), INTENT(IN) :: res, start, fin
      REAL, DIMENSION(:), INTENT(INOUT) :: vector
      INTERFACE
         FUNCTION func(vector)            
            REAL, DIMENSION(:), INTENT(IN) :: vector
            REAL :: func
         END FUNCTION func
         FUNCTION dfunc(vector)
            REAL, DIMENSION(:), INTENT(IN) :: vector
            REAL, DIMENSION(size(vector)) :: dfunc
         END FUNCTION dfunc     
      END INTERFACE   

      ! do stuff             
   END SUBROUTINE private_func

END Mod_Example

• func and dfunc would be declared within the program code that uses the MODULE Mod_Example with an interface block at the top.
• the variables: res, start etc. can be declared with values in the main program block and passed to SUBROUTINE test_routine as arguments.
• SUBROUTINE test_routine will call private_func with the variables that were passed to it.

Your main program would then look something like this:

Program Main_Program
   USE Mod_Example
   INTERFACE
      FUNCTION func(vector)            
         REAL, DIMENSION(:), INTENT(IN) :: vector
         REAL :: func
      END FUNCTION func
      FUNCTION dfunc(vector)
         REAL, DIMENSION(:), INTENT(IN) :: vector
         REAL, DIMENSION(size(vector)) :: dfunc
      END FUNCTION dfunc     
   END INTERFACE

   ! do stuff       

   ! calls test_routine form module
   ! uses dfunc and func defined below
   call test_routine(res,start,fin,vector,func,dfunc)

   ! do stuff
END PROGRAM Main_Program

! define dfunc and nfunc for passing into the modular subroutine
FUNCTION func(vector)
   IMPLICIT NONE
   REAL, DIMENSION(:), INTENT(IN) :: vector
   REAL :: func

   nfunc = vector
END FUNCTION func

FUNCTION dfunc(vector)
   IMPLICIT NONE
   REAL, DIMENSION(:), INTENT(IN) :: vector
   REAL, DIMENSION(size(vector)) :: dfunc   

   dfunc = vector
END FUNCTION dfunc