ui: Introduce (guix i18n).

* guix/ui.scm (G_, N_, _P, %gettext-domain, %package-text-domain): Move
to...
* guix/i18n.scm: ... here.  New file.

Makefile.am

@@ -103,6 +103,7 @@ MODULES =					\
   guix/store.scm				\
   guix/cvs-download.scm				\
   guix/svn-download.scm				\
+  guix/i18n.scm					\
   guix/ui.scm					\
   guix/build/ant-build-system.scm		\
   guix/build/download.scm			\

guix/i18n.scm

@@ -0,0 +1,51 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
+;;;
+;;; 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 (guix i18n)
+  #:use-module (srfi srfi-26)
+  #:export (G_
+            N_
+            P_
+            %gettext-domain
+            %package-text-domain))
+
+;;; Commentary:
+;;;
+;;; Internationalization support.
+;;;
+;;; Code:
+
+(define %gettext-domain
+  ;; Text domain for strings used in the tools.
+  "guix")
+
+(define %package-text-domain
+  ;; Text domain for package synopses and descriptions.
+  "guix-packages")
+
+(define G_ (cut gettext <> %gettext-domain))
+(define N_ (cut ngettext <> <> <> %gettext-domain))
+
+(define (P_ msgid)
+  "Return the translation of the package description or synopsis MSGID."
+  ;; Descriptions/synopses might occasionally be empty strings, even if that
+  ;; is something we try to avoid.  Since (gettext "") can return a non-empty
+  ;; string, explicitly check for that case.
+  (if (string-null? msgid)
+      msgid
+      (gettext msgid %package-text-domain)))

guix/ui.scm

@@ -26,6 +26,7 @@
 ;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
 
 (define-module (guix ui)
+  #:use-module (guix i18n)
   #:use-module (guix gexp)
   #:use-module (guix utils)
   #:use-module (guix store)
@@ -55,10 +56,8 @@
   #:use-module (texinfo)
   #:use-module (texinfo plain-text)
   #:use-module (texinfo string-utils)
-  #:export (G_
-            N_
-            P_
-            report-error
+  #:re-export (G_ N_ P_)                          ;backward compatibility
+  #:export (report-error
             leave
             make-user-module
             load*
@@ -111,26 +110,6 @@
 ;;;
 ;;; Code:
 
-(define %gettext-domain
-  ;; Text domain for strings used in the tools.
-  "guix")
-
-(define %package-text-domain
-  ;; Text domain for package synopses and descriptions.
-  "guix-packages")
-
-(define G_ (cut gettext <> %gettext-domain))
-(define N_ (cut ngettext <> <> <> %gettext-domain))
-
-(define (P_ msgid)
-  "Return the translation of the package description or synopsis MSGID."
-  ;; Descriptions/synopses might occasionally be empty strings, even if that
-  ;; is something we try to avoid.  Since (gettext "") can return a non-empty
-  ;; string, explicitly check for that case.
-  (if (string-null? msgid)
-      msgid
-      (gettext msgid %package-text-domain)))
-
 (define-syntax-rule (define-diagnostic name prefix)
   "Create a diagnostic macro (i.e., NAME), which will prepend PREFIX to all
 messages."