J3/06-217

To:      J3
From:    Bill Long
Subject: C4 - UTI 19 : interfaces for bits dummy arguments
Date:    28-jul-2006

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Unresolved Technical Issue 19 (page 46) proposes that interfaces
should be required if a dummy argument is of type bits.

Reply: This would affect only the case where there was a nonpointer
nonallocatable dummy argument of type bits. In most such cases the
corresponding actual argument will also be of type bits, in which case
an interface serves no special purpose.  The other, much less common
case is when the actual argument is of a type other than bits.  Note
that this case is quite similar to allowing rank mismatches between
actual and dummy arguments, for which we do not require an interface.
One of the uses for limited type mismatching is to allow dusty deck
codes with non-conforming data movement routines to be made conforming
by modifying only the small data movement routines. If interfaces were
required then the program would have to be modified in all the
subprograms where these routines were called, which would be a
significantly larger task, and likely unacceptable to the code's
author.  It seems that the burden of requiring the interfaces
outweighs the benefit in the cases where is matters, and it is an
unreasonable requirement in the much more common cases where the
actual and dummy argument types match.