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Re: Creating an RFC process for Perl

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From:
Craig A. Berry
Date:
June 11, 2021 21:34
Subject:
Re: Creating an RFC process for Perl
Message ID:
CA+vYcVx5VEmQHo2OXd73Un2x0d7vxutK0o3Ciwuw8UQYwZ6Lqw@mail.gmail.com
On Fri, Jun 11, 2021 at 2:34 PM Nicholas Clark <nick@ccl4.org> wrote:

> But I suspect we
> can't do long doubles and quad on some platforms, and maybe *no-one* has
> tested quad on big endian platforms before. Or VMS :-)

128-bit IEEE long doubles (also called X_FLOAT in the
DEC/Compaq/HP/HPE/VSI world) are supported on Tru64 Alpha, OpenVMS
Alpha, Linux Alpha, and OpenVMS I64.  OpenVMS x86_64 is supposed to
appear any day now in an early adopter's kit, but I don't know yet
whether its long doubles will be the 80-bit kind common on x86
platforms or one of the 128-bit types.

A few years ago Jarkko did a bunch of work classifying long doubles
(as well as other float formats) so in principle I think we have names
for where all the bits are located plus some other quirks for all the
different flavors.  The entry for longdblkind in Porting/Glossary and
the sizable chunk of real estate occupied by LONG_DOUBLEKIND in perl.h
would be starting places for prior art that may be helpful in asking
"just what kind of long double do we get on platform X?" Or maybe we
don't care about platforms as long as the formatting under discussion
here supports the 10 types Jarkko identified.

Apologies if this is all covered by the libraries mentioned up-thread;
they are all names that are new to me and I have not found the time to
educate myself yet.

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