[Rd] pari/gp interface

[Henrik Bengtsson]

On 7/25/06, Robin Hankin <r.hankin at noc.soton.ac.uk> wrote:
> Hi
>
> I'm developing an R package that
> needs to execute some code written in pari/gp.
>
> I've used this before from an R package (elliptic) but the interface
> is very
> basic: the R function creates a string such as the following:
>
> string <- echo ' ellwp ([ 2+0*I , 0+2*I ], 1+0*I )' | gp -q
>
> And then
>
> system(string)
>
> returns the output from gp which then needs to be text processed
> (translating "I"
> to "i", etc).
>
> I don't think this approach would work under Windows.

I know nothing about pari/gp, but I believe it does work on Windows
too.  There is system() command available on the Windows version too,
but with slightly different arguments (than on Linux say).

Piping is available on Windows too, e.g. "dir | sort", although you
should be able to get around that by writing to file instead and using
">" and "<".

You should be careful if your 'string' gets really long.  Then it is
much better to have a BAT file (and an sh file on Linux) to run your
external calls, alternatively you call system() multiple times.
However, I would be suprised if 'ellwp' wouldn't accept files as input
too.

/Henrik

> Does anyone have any experience of calling pari/gp from R?
>
> Or any ideas for a more portable method than the one above?
>
>
>
>
> [
> PARI/GP is a widely used computer algebra system designed for fast
> computations
> in number theory.  It is freely available at
>
>   http://pari.math.u-bordeaux.fr/
> ]
>
>
> --
> Robin Hankin
> Uncertainty Analyst
> National Oceanography Centre, Southampton
> European Way, Southampton SO14 3ZH, UK
>   tel  023-8059-7743
>
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