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

Robert Corbett Robert.Corbett
Mon Jul 28 02:16:38 EDT 2008

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.

Most of the solutions I considered would require large changes to
the standard, would impose a large burden on implementors, and
would be hard for users to understand.  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?

Bob Corbett

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