gnu: Add units.

* gnu/packages/maths.scm: New module.
* gnu-system.am (GNU_SYSTEM_MODULES): Add module.

gnu-system.am

@@ -115,6 +115,7 @@ GNU_SYSTEM_MODULES =				\
   gnu/packages/m4.scm				\
   gnu/packages/mailutils.scm			\
   gnu/packages/make-bootstrap.scm		\
+  gnu/packages/maths.scm			\
   gnu/packages/mit-krb5.scm			\
   gnu/packages/mp3.scm				\
   gnu/packages/multiprecision.scm		\

gnu/packages/maths.scm

@@ -0,0 +1,60 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2013 Andreas Enge <andreas@enge.fr>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (gnu packages maths)
+  #:use-module (gnu packages)
+  #:use-module ((guix licenses)
+                #:renamer (symbol-prefix-proc 'license:))
+  #:use-module (guix packages)
+  #:use-module (guix download)
+  #:use-module (guix build-system gnu))
+
+(define-public units
+  (package
+   (name "units")
+   (version "2.01")
+   (source (origin
+            (method url-fetch)
+            (uri (string-append "mirror://gnu/units/units-" version
+                                ".tar.gz"))
+            (sha256 (base32
+                     "1wl8kaxgk4l5jgc1f71mx1rwa6ib84krjmzyzn2f987z1g3i52qk"))))
+   (build-system gnu-build-system)
+   (synopsis "Conversion between thousands of scales")
+   (description
+    "GNU Units converts quantities expressed in various systems of
+measurement to their equivalents in other systems of measurement.  Like
+many similar programs, it can handle multiplicative scale changes.  It can
+also handle nonlinear conversions such as Fahrenheit to Celsius or wire
+gauge, and it can convert from and to sums of units, such as converting
+between meters and feet plus inches.
+
+Beyond simple unit conversions, GNU Units can be used as a general-purpose
+scientific calculator that keeps track of units in its calculations.  You
+can form arbitrary complex mathematical expressions of dimensions including
+sums, products, quotients, powers, and even roots of dimensions.  Thus you
+can ensure accuracy and dimensional consistency when working with long
+expressions that involve many different units that may combine in complex
+ways.
+
+The units are defined in an external data file.  You can use the extensive
+data file that comes with this program, or you can provide your own data
+file to suit your needs.  You can also use your own data file to supplement
+the standard data file.")
+   (license license:gpl3+)
+   (home-page "http://www.gnu.org/software/units/")))