Here is a recipe:

(define-public fplll

(package

(name "fplll")

(version "4.0.1")

(source (origin

(method url-fetch)

(uri (string-append

"http://perso.ens-lyon.fr/damien.stehle/fplll/libfplll-" version ".tar.gz"))

(sha256 (base32

"122bpqdlikshhd7nmq0l5qfc0agyk7x21gvplv1l9hb77l8cy9rw"))))

(build-system gnu-build-system)

(inputs `(("gmp" ,gmp)

("mpfr" ,mpfr)))

(synopsis "fplll, a library for LLL-reduction of euclidean lattices")

(description

"fplll LLL-reduces euclidean lattices. Since version 3, it can also solve the shortest vector problem.")

(license "LGPLv2.1")

(home-page "http://perso.ens-lyon.fr/damien.stehle/fplll/")))

It could go into multiprecision.scm, or get its own file.

Andreas