emacs half window scroll

;;; This paste is basically redundant. After I wrote the functions, I did some
;;; internet searching and found that these following functions are already in
;;; view.el, a part of the core emacs code. No regrets at writing them, because
;;; I learned more about elisp in the process.

;; View-scroll-half-page-forward
;; View-scroll-half-page-backward

;;; I'm still debating if I want to bind the View-* commands to keys and/or
;;; aliases.

;; Commands

(defun scroll-up-half-window ()
  (interactive)
  (goto-center-row)
  (recenter-top-bottom 0))

(defun scroll-down-half-window ()
  (interactive)
  (goto-center-row)
  (recenter-top-bottom -1))

;; Support function
(defun goto-center-row ()
  (let ((recenter-positions  '(middle top bottom)))
    (move-to-window-line-top-bottom)))