(j3.2006) Parent component of extension of abstract type

[Bill Long]

On Nov 12, 2015, at 4:20 PM, Van Snyder <Van.Snyder at jpl.nasa.gov> wrote:

> On Thu, 2015-11-12 at 22:13 +0000, Bill Long wrote:
>> On Nov 12, 2015, at 3:32 PM, Van Snyder <Van.Snyder at jpl.nasa.gov> wrote:
>> 
>>> It seems a bit strange that I can't access the parent component of an
>>> object of a type that is an extension of an abstract type, but I can
>>> access components of the parent component.  Is this what we intended?
>> 
>> You?re not allowed to declare an object of an abstract type.  So it
>> would seem odd to allow a designator for an object of an abstract
>> type. 
> 
> According to the definition of type extension, an extension of an
> abstract type has a component of abstract type.  But it can't be
> accessed as a whole.  But its components can be accessed even if its
> name appears in the <data-ref>.

But those components are not of abstract type, so it seems ok. 

> 
> Maybe we should allow to instantiate nonpolymorphic objects of abstract
> type, but prohibit invoking deferred type-bound procedures using one as
> the <data-ref>.

Deferred usually means ?doesn?t exist yet?.   So, I agree that invoking a deferred tbp is a not a good idea. 

If you want to instantiate objects of the abstract type, just don?t make the type abstract. 

Cheers,
Bill



> 
>> Cheers,
>> Bill
>> 
>>> 
>>> program P
>>> 
>>> type, abstract :: T0
>>>   integer :: N = 42
>>> end type T0
>>> 
>>> type, extends(t0) :: T1
>>> end type T1
>>> 
>>> type(t1) :: V1, V2
>>> 
>>> print '(a,i0)', 'V1 ', v1
>>> print '(a,i0)', 'V1%T0 ', v1%t0      ! Prohibited
>>> print '(a,i0)', 'V1%T0%n ', v1%t0%n
>>> 
>>> v2 = v1
>>> v2%t0 = v1%t0                        ! Prohibited
>>> v2%t0%n = v1%t0%n
>>> 
>>> end program P
>>> 
>>> 
>>> _______________________________________________
>>> J3 mailing list
>>> J3 at mailman.j3-fortran.org
>>> http://mailman.j3-fortran.org/mailman/listinfo/j3
>> 
>> Bill Long                                                                       longb at cray.com
>> Fortran Technical Support  &                                  voice:  651-605-9024
>> Bioinformatics Software Development                     fax:  651-605-9142
>> Cray Inc./ Cray Plaza, Suite 210/ 380 Jackson St./ St. Paul, MN 55101
>> 
>> 
> 
> 
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Bill Long                                                                       longb at cray.com
Fortran Technical Support  &                                  voice:  651-605-9024
Bioinformatics Software Development                     fax:  651-605-9142
Cray Inc./ Cray Plaza, Suite 210/ 380 Jackson St./ St. Paul, MN 55101