[J3] New intrinsic XXX_PREFIX and XXX_SUFFIX procedures

[Van Snyder]

On Thu, 2023-01-26 at 23:52 +0000, Brad Richardson via J3 wrote:
> Hi Van,
> 
> I'm not quite sure I understand the use case your suggesting. What
> would it mean to provide an enumerator as an OPERATION? Can you
> provide an example?

Assume there is an enumeration type SCAN_OPERATIONS in ISO_Fortran-Env,
and one of the enumerators is SCAN_SUM. then you'd invoke the SCAN
instrinsic using
   
   SCAN ( ARRAY, SCAN_SUM )
   
As I mentioned in reply to Tom's question, if the OPERATION isn't a
function, it ought to be an enumerator, i.e., a constant, so the
processor knows which scan to do at compile time. If you want it to be
a run-time selection, use the form in which OPERATION is a function,
and put your decision inside of it.

Alternatively, one could allow the OPERATION to be a variable of the
enumeration type, with a note that this might be less efficient because
the processor doesn't know which operation to do at compile time. It's
kine of like the processor optimizing sqrt(2.0) when it sees that,
instead of

  x = 2.0
 print *, sqrt(x)

> Regards,
> Brad
> 
> On Thu, 2023-01-26 at 10:45 -0800, Van Snyder via J3 wrote:
> > On Thu, 2023-01-26 at 16:52 +0000, Brad Richardson via J3 wrote:
> > > I've been pondering this more, and I think the way I'd like to
> > > propose
> > > this is as a single new intrinsic. I think it could in theory be
> > > named
> > > SCAN, as the interface would be fully distinguishable from the
> > > existing
> > > SCAN intrinsic for character set membership search. The interface
> > > would
> > > be:
> > > 
> > > SCAN(ARRAY, OPERATION[, IDENTITY, DIM, MASK, SEGMENT, EXCLUSIVE,
> > > REVERSED, ORDERED])
> > 
> > There should be two varieties of OPERATION. One would be an
> > enumerator of an enumeration type defined in ISO_Fortran_Env. The
> > other would be a two-argument function provided by the user.
> > 

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