Add some packages

emacs/.emacs.d/init.el

@@ -26,6 +26,49 @@
 
 ;;; Code:
 
+;;;; Package configuration:
+;;; Require package.el since we immediately start using its variables
+;;; and functions anyway, no need to delay loading.
+(require 'package)
+
+;; Add the MELPA and org package archives because I like living on the
+;; bleeding edge. This should be done both at run-time and
+;; compile-time so I can install packages at compile time.
+(eval-and-compile
+  (add-to-list 'package-archives '("melpa" . "https://melpa.org/packages/"))
+  (add-to-list 'package-archives '("org" . "http://orgmode.org/elpa/")))
+
+;; Initialize package.el so that packages can be loaded and used. This
+;; also needs to be done at both run-time and compile-time so packages
+;; can be installed at compile-time.
+(eval-and-compile (package-initialize))
+
+;; Refresh the package contents so packages can be installed from all
+;; configured archives. Don't do this at run-time because it slows
+;; down the process too much.
+(eval-when-compile (package-refresh-contents))
+
+;; This macro is inspired by use-package, but I want to maintain some
+;; control of the syntax I use to configure my settings.
+(defmacro ensure-package (package &rest args)
+  "Make sure PACKAGE is installed.
+
+ARGS should be a plist which may contain one of the following options:
+
+- :from
+
+  Specify which package should actually be installed to ensure
+  the library named in PACKAGE exists."
+  (let ((library-symbol (cl-gensym))
+        (package-symbol (cl-gensym)))
+    `(eval-when-compile
+       (let ((,library-symbol ',package)
+             (,package-symbol ',(or (plist-get args :from) package)))
+         (unless (and (package-installed-p ,package-symbol)
+                      (locate-library (symbol-name ,library-symbol)))
+           (package-install ,package-symbol))
+         (require ,library-symbol)))))
+
 ;;;; Helper functions:
 
 ;; I have noticed that I refer to the combination of
@@ -107,5 +150,23 @@ This is currently the data directory under the
 ;; whereabouts I am, so they just take up space.
 (scroll-bar-mode -1)
 
+;;;; Minor modes:
+
+;;;;; Paredit:
+
+(ensure-package paredit)
+
+;;;; Major modes:
+
+;;;;; Scheme mode:
+
+(add-hook 'scheme-mode-hook 'paredit-mode)
+
+;;;; Applications:
+
+;;;;; Magit:
+
+(ensure-package magit)
+
 (provide 'init)
 ;;; init.el ends here