11.2 Data declaration

• [5.3] If an object is initialised (in a type declaration statement or component definition statement), its array bounds and character length can be used in its initialisation expression.
• [7.0] The EQUIVALENCE and COMMON statements, and the BLOCK DATA program unit, are considered to be obsolescent (and reported as such when the -f2018 option is used).
• [7.1] Assumed-rank dummy arguments accept actual arguments of any rank; they assume the rank from the actual argument. This rank may be zero; that is, the actual argument may be scalar. Furthermore, assumed-rank dummy arguments may have the ALLOCATABLE or POINTER attribute, and thus accept allocatable/pointer variables of any rank.

  The syntax is as follows:

    Real,Dimension(..) :: a, b
    Integer :: c(..)
  

  That declares three variables (which must be dummy arguments) to be assumed-rank.

  The use of assumed-rank dummy arguments within Fortran is extremely limited; basically, the intrinsic inquiry functions can be used, and there is a SELECT RANK construct, but other than that they may only appear as actual arguments to other procedures where they correspond to another assumed-rank argument.

  The main use of assumed rank is for advanced C interoperability (see later section).

  Here is an extremely simple example of use within Fortran:

    Program assumed_rank_example
      Real x(1,2),y(3,4,5,6,7)
      Call showrank(1.5)
      Call showrank(x)
      Call showrank(y)
    Contains
      Subroutine showrank(a)
        Real,Intent(In) :: a(..)
        Print *,'Rank is',Rank(a)
      End Subroutine
    End Program
  

  That will produce the output

   Rank is 0
   Rank is 2
   Rank is 5
  

• [7.1] The TYPE(*) type specifier can be used to declare scalar, assumed-size, and assumed-rank dummy arguments. Such an argument is called assumed-type; the corresponding actual argument may be of any type. It must not have the ALLOCATABLE, CODIMENSION, INTENT (OUT), POINTER, or VALUE attribute.

  An assumed-type variable is extremely limited in the ways it can be used directly in Fortran:

  • it may be passed as an actual argument to another assumed-type dummy argument;
  • it may appear as the first argument to the intrinsic functions IS_CONTIGUOUS, LBOUND, PRESENT, SHAPE, SIZE, or UBOUND;
  • it may be used as the argument of the function C_LOC (in the ISO_C_BINDING intrinsic module}.
  Other than these contexts, it cannot be used in any other way at all. Note that if it is an array, you cannot subscript it or create an array section from it.

  This is mostly useful for interoperating with C programs (see later section).