Emacs macro to ensure that a package is installed before configuring

ensure-installed-package.el

(defmacro ensure-installed-package (package &rest body)
  "Ensures PACKAGE is installed and then performs body. Place package configurations in BODY"
  (declare (indent 1))    
  `(progn 
     (when (not (package-installed-p ,package))
       (package-install ,package))
     ,@body))


;; USAGE:
(ensure-installed-package 'haskell-mode
  ;; Configure package here
  (add-hook 'haskell-mode-hook 'turn-on-haskell-indent))