Re: [bug-gawk] missing function powm and friends

[Aharon Robbins]

Hi Michael.

Thank you for your offer of the new functions. I appreciate your
willingness to contribute.

> Date: Thu, 27 Nov 2014 14:45:24 -0500
> From: "Andrew J. Schorr" <address@hidden>
> To: Michael Plugge <address@hidden>
> Cc: address@hidden
> Subject: Re: [bug-gawk] missing function powm and friends
>
> On Thu, Nov 27, 2014 at 03:49:37PM +0100, Michael Plugge wrote:
> > I wrote a small patch to use the powm() function (and also gcd() and
> > next_prime()) of gmp; this works even for very large parameters and
> > exponents. The appended patch file includes also an integer version of the
> > routines. It would be really great if it could be integrated into gawk :-).
>
> I wish we could simply package this as a shared library extension, but the
> problem is that the extension mechanism passes numeric values as double
> precision numbers and does not expose the MPFR/GMP numbers used with -M.  The
> gawk-mpfr extension converts numbers to strings in order to pass them between
> gawk and the library, so that is one approach to dealing with this.

I would recommend this as the way to make a first attempt at
packaging up these functions as an extension.

> My sense is that there's a limited appetite for adding new functions to
> gawk, and a preference for adding new functionality through extensions.

That is exactly right. I think these functions would be useful if
available as an extension.  Michael, can you work with Andy to package
them into gawkextlib, either as part of the MPFR extension or as a small
standalone extension?

Another option might be to write them entirely in awk using basic
mathematical operations and assuming the availability of -M.

> But it is challenging when considering extensions that would benefit
> from the arbitrary-precision representation.  Maybe it's worth giving
> some thought to how to enhance the shared library interface to support
> alternate numeric representations.  That may be a big job.

This is worth some thought, but since it's not likely to happen very
soon, I suggest that you and Michael work to get his code into gawkextlib
now. It can be revised later once the gawk team figures out if and how
to pass MPFR values to/from an extension.

Thanks!

Arnold