gnu: Add emacs-constants.

* gnu/packages/emacs.scm (emacs-constants): New variable.
* gnu/packages/patches/emacs-constants-lisp-like.patch: New patch.
* gnu-system.am (dist_patch_DATA): Add it.

gnu-system.am

@@ -452,6 +452,7 @@ dist_patch_DATA =						\
   gnu/packages/patches/duplicity-piped-password.patch		\
   gnu/packages/patches/duplicity-test_selection-tmp.patch	\
   gnu/packages/patches/elfutils-tests-ptrace.patch		\
+  gnu/packages/patches/emacs-constants-lisp-like.patch		\
   gnu/packages/patches/emacs-exec-path.patch			\
   gnu/packages/patches/emacs-scheme-complete-scheme-r5rs-info.patch	\
   gnu/packages/patches/emacs-source-date-epoch.patch		\

gnu/packages/emacs.scm

@@ -26,6 +26,9 @@
   #:use-module (guix packages)
   #:use-module (guix download)
   #:use-module (guix git-download)
+  #:use-module (guix gexp)
+  #:use-module (guix monads)
+  #:use-module (guix store)
   #:use-module (guix build-system gnu)
   #:use-module (guix build-system emacs)
   #:use-module (guix build-system glib-or-gtk)
@@ -1297,3 +1300,41 @@ to a key in your preferred mode.")
      "This package provides a set of Emacs functions to search definitions of
 identifiers in the MIT-Scheme documentation.")
     (license license:gpl2+)))
+
+;;; XXX: move this procedure to an utility module
+(define* (uncompressed-file-fetch url hash-algo hash
+                                  #:optional name
+                                  #:key (system (%current-system))
+                                  (guile (default-guile)))
+  (mlet %store-monad ((drv (url-fetch url hash-algo hash name
+                                      #:system system
+                                      #:guile guile)))
+    (gexp->derivation (or name (basename url))
+                      #~(begin
+                          (mkdir #$output)
+                          (setenv "PATH"
+                                  (string-append #$gzip "/bin"))
+                          (chdir #$output)
+                          (copy-file #$drv (basename #$url))))))
+
+(define-public emacs-constants
+  (package
+    (name "emacs-constants")
+    (version "2.2")
+    (source
+     (origin
+       (file-name (string-append name "-" version ".el"))
+       (method uncompressed-file-fetch)
+       (uri "https://staff.fnwi.uva.nl/c.dominik/Tools/constants/constants.el")
+       (patches
+        (list (search-patch "emacs-constants-lisp-like.patch")))
+       (sha256
+        (base32
+         "14q094aphsjhq8gklv7i5a7byl0ygz63cv3n6b5p8ji2jy0mnnw3"))))
+    (build-system emacs-build-system)
+    (home-page "https://staff.fnwi.uva.nl/c.dominik/Tools/constants")
+    (synopsis "Enter definition of constants into an Emacs buffer")
+    (description
+     "This package provides functions for inserting the definition of natural
+constants and units into an Emacs buffer.")
+    (license license:gpl2+)))

gnu/packages/patches/emacs-constants-lisp-like.patch

@@ -0,0 +1,81 @@
+Add Scheme support
+
+--- constants/constants.el.orig	2015-12-26 17:44:31.734520833 +0100
++++ constants/constants.el	2015-12-30 17:41:28.402871263 +0100
+@@ -684,6 +684,33 @@
+ 
+ (eval-when-compile (defvar ctable))
+ 
++(defun constants-is-lisp-like (mode)
++  (save-match-data
++    (string-match "\\(lisp\\|scheme\\)" (symbol-name mode))))
++
++(defun constants-is-set-like ()
++  (save-excursion
++    (condition-case nil
++        (save-match-data
++          (progn (up-list -1)
++                 (or (looking-at "(set[qf!]?\\>") (looking-at "(define\\>"))))
++      (error nil))))     ; return value nil means use default
++
++;;;###autoload
++(defun constants-lisp-like-function ()
++  "Check context for constants insertion."
++  (if (constants-is-set-like)
++      '(emacs-lisp-mode "%n %v%t; %d %u" "e" "(* %p %v)")
++    '(emacs-lisp-mode "(%n %v)%t; %d %u" "e" "(* %p %v)")))
++
++;;;###autoload
++(mapc (lambda (mode-hook)
++        (add-hook mode-hook
++                  (lambda ()
++                    (setq constants-language-function
++                          'constants-lisp-like-function))))
++      '(scheme-mode-hook emacs-lisp-mode-hook lisp-mode-hook))
++
+ ;;;###autoload
+ (defun constants-insert (&optional unit-system names)
+   "Insert one or more natural constant definitions in source code.
+@@ -826,8 +853,9 @@
+             (funcall process-func ins))
+         ;; Here comes the insertion stuff for source code editing modes.
+         ;; First make sure we start a new line
+-        (if (string-match
+-             "\\S-" (buffer-substring (point-at-bol) (point-at-eol)))
++        (if (and (string-match
++                  "\\S-" (buffer-substring (point-at-bol) (point-at-eol)))
++                 (not (constants-is-lisp-like mode)))
+             ;; non-empty line, insert after this line
+             (progn 
+               (end-of-line 1) 
+@@ -841,13 +869,24 @@
+           (if (string-match "\\(.*\\)%t\\(.*\\)" line)
+               (let ((comment-column 42))
+                 (insert (match-string 1 line))
+-                (indent-to comment-column)
+-                (insert (match-string 2 line)))
++                (if (and (constants-is-lisp-like mode)
++                         (or (constants-is-set-like)
++                             (null clist)))
++                    (save-excursion
++                      (progn
++                        (move-to-column comment-column t)
++                        (insert (match-string 2 line))
++                        ;; insert a newline such that paredit's M-) can mode
++                        ;; the closing parentheses to the next line.
++                        (newline-and-indent)))
++                  (progn
++                    (indent-to comment-column)
++                    (insert (match-string 2 line)))))
+             (insert line)))
+-        (if constants-indent-code
+-            (newline-and-indent)
+-          (newline))))))
+-
++        (unless (and (constants-is-lisp-like mode) (null clist))
++          (if constants-indent-code
++              (newline-and-indent)
++            (newline)))))))
+ ;;;###autoload
+ (defun constants-get (&optional const message)
+   "Return the value of CONST as defined in the constants package.