(j3.2006) [Re: Types need a "self" component ]

[Van Snyder]

On Dec 17, 2015, at 9:29 PM, Van Snyder <van.snyder at jpl.nasa.gov>
wrote:

> > It's not possible to assign to a nonallocatable polymorphic object, or
> > to the declared-type part of it, without mentioning all the components
> > of the declared type individually, even if the class is not abstract.
> 
> > If a type had a nonpolymorphic "self" component of the same name and
> > type as itself, encompassing all its components in the same way a parent
> > component encompasses all its components, it would be possible to assign
> > to the declared-type part of a polymorphic object, without mentioning
> > all the components individually.
> >
> > type :: T1
> >  integer :: A
> >  integer :: B
> >  ...
> >  integer :: Z
> > end type T1
> >
> > class(t1) :: V1
> > type(t1) :: V2
> >
> > v1 = v2    ! prohibited
> > v1%t1 = v2 ! would be nice, but we didn't do it

> I thought that 

> select type (V1)
> type is (t1) 
>    v1 = v2
> class default
>    v1%t1 = v2
> end select

> was designed to handle this type of problem. 

v1%t1 = v2

never works, because the declared type of v1 does not have a t1
component, no matter what its dynamic type is.  If the declared type of
v1 were an extension of t1, it would work.