An elisp snippet for quickly getting Clojure and tooling support into Emacs

quick-clojure.el

;;
;; Evaluate the form below or add it to your Emacs initialization file
;; to add Clojure support to Emacs.
;;
;; Required system dependencies:
;; - JDK 1.7+
;; - wget
;;
(let* ((github-url        "https://raw.githubusercontent.com/")
       (lein-url          (concat github-url "technomancy/leiningen/stable/bin/lein"))
       (lein-install-path (concat user-emacs-directory "lein"))
       (lein-installed?   (not (string= "" (shell-command-to-string "which lein")))))

  (when (not lein-installed?)
    (message "Installing Clojure runtime (may take a while)...")
    (shell-command-to-string
     (concat "wget -O " lein-install-path " " lein-url))
    (shell-command-to-string
     (concat "chmod +x " lein-install-path))
    (shell-command-to-string
     lein-install-path))

  (when (or (not (boundp 'package-archives))
            (not (assoc "melpa" package-archives))
            (not (fboundp 'cider-jack-in)))
    (message "Configuring Emacs package manager...")
    (require 'package)
    (add-to-list 'package-archives '("melpa" . "http://melpa.org/packages/") t)
    (package-initialize)
    (package-refresh-contents))
  
  (message "Checking Clojure support in Emacs...")
  (when (not (package-installed-p 'cider))
    (package-install 'cider)
    (customize-set-variable 'cider-allow-jack-in-without-project t))
  (when (not lein-installed?)
    (customize-set-variable 'cider-lein-command lein-install-path))
  (when (not (package-installed-p 'paredit))
    (package-install 'paredit)
    (add-hook 'clojure-mode-hook 'enable-paredit-mode)
    (add-hook 'cider-repl-mode-hook 'enable-paredit-mode))
  (when (not (package-installed-p 'company))
    (package-install 'company)
    (add-hook 'clojure-mode-hook 'company-mode)
    (add-hook 'cider-repl-mode-hook 'company-mode))

  (message "Ready. Run `M-x cider-jack-in' to start a Clojure REPL."))