(j3.2006) derived types with type parameters are different

[Bill Long]

Robert Corbett wrote:
> After spending more time than I should have searching for a good
> solution to this problem, I have concluded that there are no good
> solutions.  I have decided that the best fix for the problem is
> to ban sequence types with type parameters from standard-conforming
> programs.  Given the permissive nature of the Fortran standard,
> vendors who currently implement sequence types with type parameters
> could continue to support them unchanged.
>   

I'm not sure what is being proposed here.  Is it

1) An Interp for Fortran 2003 along the lines of "you guys really didn't 
intend to allow this; it is certainly a mistake in the standard..."  or

2) A comment for Fortran 2008 that we should make an incompatible change 
that removes this capability.



> Most of the solutions I considered would require large changes to
> the standard, 

I would not consider something that requires large changes to the 
standard to be a "solution".

> would impose a large burden on implementors, 

"did impose" for those who already did this, "would impose" for the rest.

> and
> would be hard for users to understand.  

As compared to, for example, finalizers ?

> Simple solutions, such as
> considering all derived type definitions with type parameters to
> define different types, would almost certainly break all
> existing implementations of parameterized sequence types.  Given
> that parameterized sequence types add negligible functionality to
> the language, why bother?
>   

I think the time for that argument was about 6 years ago. 

Cheers,
Bill


> Bob Corbett
> _______________________________________________
> J3 mailing list
> J3 at j3-fortran.org
> http://j3-fortran.org/mailman/listinfo/j3
>   

-- 
Bill Long                                   longb at cray.com
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