Re: +-Inf and NaN

I think that using exactly the same argument conventions and names as the
library would be best.
so you overwrite one (or more) of the inputs, for the same reasons as mpfr
does it,
to save memory allocation when possible.

Possible glitch:  it assumes you will only pass arguments that are in
memory, not on a stack.
Thus for actual use you may need to have a functional style program
interface that puts the
arguments in memory.  I think that mpfr number structures have a size
[maximum length] and
an actual size in use. So numbers and comparisons of them etc. must be done
by mpfr.
RJF


On Wed, Feb 28, 2024 at 12:55 PM Camm Maguire <[email protected]>
wrote:

> Greetings!
>
> Richard Fateman <[email protected]> writes:
>
> > Several of us here have worked on arbitrary-precision floats in Lisp
> > (generally used for longer than double, though I suppose shorter could
> > also be specified...), and I think the real win would be to make use
> > of the mpfr library (written in C with various assembly-language hacks
> > for different CPUs).
>
> mpfr would be a straightforward extension to GCL, as we already use the
> gmp integer library, integrate it with our gbc/memory management, and
> export the functions at the lisp user level:
>
>
> >(gmp:mpz_mul most-positive-fixnum most-positive-fixnum)
>
> 85070591730234615847396907784232501249
>
> The only sensible way to interface to a library like this is to keep all
> the function names and calling syntax the same.  GMP is written with
> 'side-effects', i.e. destructive modification of the supplied arguments
> one or more of which are considered outputs.  This is so the savvy user
> can avoid unnecessary allocations, which are effectively all that matter
> for performance.  Lisp is so functionally oriented, however, that it
> seemed better to me to take only input variables as arguments.  The
> natural alternative to the call above would take three arguments,
> overwrite the first, and return no values.  Your thoughts?
>
> Take care,
> --
> Camm Maguire                                        [email protected]
> ==========================================================================
> "The earth is but one country, and mankind its citizens."  --  Baha'u'llah
>

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