To: J3                                                     J3/18-128
From: Tom Clune
Subject: Associating REAL and COMPLEX entities
Date: 2018-February-14

A somewhat common situation in spectral methods (i.e., when using
Fourier transforms), is to alternately treat the data as REAL and
COMPLEX depending on context.  Indeed, some real-to-complex and
complex-to-real transforms are implemented in-place.

Early versions of Fortran supported such mixed treatment of a single
array, but the required features are all now deprecated in favor of
stronger typing rules.  However, because of the strong storage
assocation requirements for REAL and COMPLEX types, a small relaxation
of the typing rules is warranted.

The concept would be to provide a mechanism to associate something
like a REAL pointer with a COMPLEX target.

Note: The opposite case, i.e., associating a COMPLEX pointer with a
REAL target is also of interest, but problematic due the possibility
that the REAL target does not have an even number of elements.