pointer to available datatype

[ya0037]

Hellow everybody,

I am wondering whether there would be a way in FORTRAN to get a pointer address to an available datatype.

For example:
I have the below data type

module dt
type data
integer, dimension(3) :: comp
real, dimension(:), pointer :: a => null
end type 
end module dt

and I would create

program test
use dt
implicit none
type(data) :: mytype
end program test

Now I am wondering defining mytype, is there anyway I can get a pointer address to this type.

Thanks a lot in advance.
Cheers,

 

[salgerman]

What have you tried? Have you read up on Fortran 90 Pointers at all?

I am not even sure what your are asking; in fact, your question seems mis-constructed to me..."pointer address"? Did you mean to say "address pointer"?

To tell you the truth, I am yet to use pointers in Fortran; but, a bit of reading triggered by your post revealed that pointers and addresses are 2 different things and, apparently, Fortran (unlike C) tends to hide such inner-details from the programmer...this has been on purpose, by the way, and that is why it has been very difficult to produce memory-related problems in Fortran.

Getting back to your "pointer address":
Do you really need the address? or
Do you just need the ability to use pointers?

 

[FJacq]

module dt
  type data
    integer, dimension(3) :: comp
    real, dimension(:), pointer :: a => null() ! notice the difference with your version
  end type 
end module dt 

program test
  use dt
  implicit none
  type(data),target :: mytype
  type(data),pointer :: mytype2
  real, dimension(:), pointer :: vect
  mytype2=> mytype ! mytype2 becomes an alias of mytype
  allocate(vect(10)) ! usually, I only allocate allocatable objects but for you ...
  vect=5
  mytype2%a => vect
  write(*,*) mytype%a ! I hope 10 values equal to 5
end program test

François Jacq