Fortran Data Types Assumed and deferred length type parameters
Example
Variables of character type or of a derived type with length parameter may have the length parameter either assumed or deferred. The character variable name
character(len=len) name
is of length len throughout execution. Conversely the length specifier may be either
character(len=*) ... ! Assumed length
or
character(len=:) ... ! Deferred length
Assumed length variables assume their length from another entity.
In the function
function f(dummy_name)
character(len=*) dummy_name
end function f
the dummy argument dummy_name has length that of the actual argument.
The named constant const_name in
character(len=*), parameter :: const_name = 'Name from which length is assumed'
has length given by the constant expression on the right-hand side.
Deferred length type parameters may vary during execution. A variable with deferred length must have either the allocatable or pointer attribute
character(len=:), allocatable :: alloc_name
character(len=:), pointer :: ptr_name
Such a variable's length may be set in any of the following ways
allocate(character(len=5) :: alloc_name, ptr_name)
alloc_name = 'Name' ! Using allocation on intrinsic assignment
ptr_name => another_name ! For given target
For derived types with length parameterization the syntax is similar
type t(len)
integer, len :: len
integer i(len)
end type t
type(t(:)), allocatable :: t1
type(t(5)) t2
call sub(t2)
allocate(type(t(5)) :: t1)
contains
subroutine sub(t2)
type(t(*)), intent(out) :: t2
end subroutine sub
end
