CODEWITHSUNDEEP
polymorphismfortran
alexis
alexis

Reputation: 430

Allocate Type in Polymoprhic Variable Fortran

I am trying to use polymorphism in Fortran, but I have problems allocating the type. I can't figure out how make this work. The Intel compiler threw this error:

error #6460: This is not a field name that is defined in the encompassing structure.
analitic%param%a0=2
---------------^

Here is a minimal example:

program new

implicit none

integer, parameter    :: dp = kind(1.0d0)

type :: potential
  class(*),allocatable                        :: param
endtype

type(potential)          :: analitic
type  :: pa1d_param
  real(dp)     :: a0
  real(dp)     :: b0
end type

allocate(pa1d_param::analitic%param)

analitic%param%a0=2.0_dp     

end program

What is wrong here?

Thank you!

Upvotes: 0

Views: 1474

Answers (1)

milancurcic
milancurcic

Reputation: 6241

By declaring param as class(*), you are declaring an unlimited polymorphic object. These cannot be referenced in a normal way - they can only be used as actual arguments, pointers or targets in pointer assignment, or as selectors in select type statements (16.3.1, Fortran 95/2003 explained, Metcalf and Reid).

In order to do this as you intended, you will have to declare param this way: (compiles and produces correct output with ifort 12.0.2.137)

program new

 implicit none

 integer, parameter :: dp = kind(1.0d0)

 type pa1d_param
   real(dp) :: a0
   real(dp) :: b0
 end type pa1d_param

 type :: potential
   class(pa1d_param),allocatable :: param
 endtype

 type(potential)          :: analitic

 allocate(analitic%param)

 analitic%param%a0 = 2.0_dp

 write(*,*)analitic%param%a0

end program

Upvotes: 2

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