Fancy unicode arrows for emacs scala-mode. Done this way because I don't think it can work as an abbrev.

scala-arrows.el

(defun right-arrow ()
  (interactive)
  (cond ((looking-back "=") 
   (backward-delete-char 1) (insert "⇒"))
	((looking-back "-")
	 (backward-delete-char 1) (insert "→"))
	(t (insert ">"))))

(defun left-arrow ()
  (interactive)
  (if (looking-back "<") 
      (progn (backward-delete-char 1)
	     (insert "←"))
    (insert "-")))


(add-hook 'scala-mode-hook '(lambda () (interactive) 
			      (local-set-key (kbd "-") 'left-arrow)
			      (local-set-key (kbd ">") 'right-arrow)))