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+;;; guix-location.el --- Package locations
+
+;; Copyright © 2016 Alex Kost <alezost@gmail.com>
+
+;; 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 Location as published by
+;; the Free Software Foundation, either version 3 of the Location, 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 Location for more details.
+
+;; You should have received a copy of the GNU General Public Location
+;; along with this program.  If not, see <http://www.gnu.org/locations/>.
+
+;;; Commentary:
+
+;; This file provides the code to work with locations of Guix packages.
+
+;;; Code:
+
+(require 'cl-lib)
+(require 'guix-backend)
+(require 'guix-read)
+(require 'guix-guile)
+
+(defun guix-package-location (id-or-name)
+  "Return location of a package with ID-OR-NAME.
+For the meaning of location, see `guix-find-location'."
+  (guix-eval-read (guix-make-guile-expression
+                   'package-location-string id-or-name)))
+
+(defun guix-find-location (location &optional directory)
+  "Go to LOCATION of a package.
+LOCATION is a string of the form:
+
+  \"PATH:LINE:COLUMN\"
+
+If PATH is relative, it is considered to be relative to
+DIRECTORY (`guix-directory' by default)."
+  (cl-multiple-value-bind (path line col)
+      (split-string location ":")
+    (let ((file (expand-file-name path (or directory guix-directory)))
+          (line (string-to-number line))
+          (col  (string-to-number col)))
+      (find-file file)
+      (goto-char (point-min))
+      (forward-line (- line 1))
+      (move-to-column col)
+      (recenter 1))))
+
+;;;###autoload
+(defun guix-edit (id-or-name &optional directory)
+  "Edit (go to location of) package with ID-OR-NAME.
+See `guix-find-location' for the meaning of package location and
+DIRECTORY.
+Interactively, with prefix argument, prompt for DIRECTORY."
+  (interactive
+   (list (guix-read-package-name)
+         (guix-read-directory)))
+  (let ((loc (guix-package-location id-or-name)))
+    (if loc
+        (guix-find-location loc directory)
+      (message "Couldn't find package location."))))
+
+(provide 'guix-location)
+
+;;; guix-location.el ends here