CODEWITHSUNDEEP
oopfortranfortran90derived-types
lenzinho
lenzinho

Reputation: 401

Fortran dynamic field reference?

Is it possible to refer to a derived type field in Fortran dynamically? I want to achieve something to the effect of what can be done in Matlab:

fldnm = 'fred';
s.(fldnm) = 18;
y = s.(fldnm)

See these links (for Matlab examples): http://blogs.mathworks.com/loren/2005/12/13/use-dynamic-field-references/ http://www.mathworks.com/help/matlab/matlab_prog/generate-field-names-from-variables.html

Thanks!

Upvotes: 0

Views: 132

Answers (1)

IanH
IanH

Reputation: 21431

No. Perhaps you need to store both the field name and value in a data object, rather than trying to use components for the field name.

Otherwise you would need to wrap the reference or definition of the component of the object of derived type with a SELECT CASE statement or similar.

TYPE :: t
  INTEGER :: fred
  INTEGER :: roger
  INTEGER :: bill
END TYPE t

SUBROUTINE set(object, name, value)
  TYPE(t), INTENT(INOUT) :: object
  CHARACTER(*), INTENT(IN) :: name
  INTEGER, INTENT(IN) :: value
  SELECT CASE (name)
  CASE ('fred')  ; object%fred = value
  CASE ('roger') ; object%roger = value
  CASE ('bill')  ; object%bill = value
  END SELECT
END SUBROUTINE set

FUNCTION get(object, name)
  TYPE(t), INTENT(IN) :: object
  CHARACTER(*), INTENT(IN) :: name
  INTEGER :: get
  SELECT CASE (name)
  CASE ('fred')  ; get = object%fred
  CASE ('roger') ; get = object%roger
  CASE ('bill')  ; get = object%bill
  END SELECT
END FUNCTION get

TYPE(t) :: s
CALL set(s, 'fred', 18)
y = get(s, 'fred')

Upvotes: 2

Related Questions