commands for interactive programming with GHCi in emacs.

emacs-with-ghci.el

(defun altech-define-haskell-hook ()

  (defun code-to-list (str)
    (split-string
     (replace-regexp-in-string "^\n+" ""
    	       (replace-regexp-in-string "\n+$" "" str)) "\n"))

  (defun send-line-to-ghci (line)
    (insert line)
    (eshell-send-input)
    (sleep-for 0.2)
    (goto-char (point-max)))

  (defun send-code-to-ghci (with-let)
    (let* ((is-use-region (use-region-p)) (code (if is-use-region (code-to-list (buffer-substring-no-properties (region-beginning) (region-end))))))
      (unless (get-buffer "*ghci*")
	(with-current-buffer (generate-new-buffer "*ghci*")
	  (eshell-mode)
	  (send-line-to-ghci "ghci")
	  (sleep-for 1)))
      (progn
	(with-current-buffer "*ghci*"
	  (goto-char (point-max))
	  (if (not is-use-region)
	      (send-line-to-ghci ":l test")
	    (princ code)
	    (send-line-to-ghci ":{")
	    (if with-let
		(send-line-to-ghci "let"))
	    (dolist (line code)
	      (send-line-to-ghci line))
	    (send-line-to-ghci ":}"))))))

  (defun send-code-to-ghci-and-switch (with-let)
    (send-code-to-ghci with-let)
    (other-window-or-split)
    (switch-to-buffer "*ghci*")
    (goto-char (point-max))
    (end-of-buffer)
    (recenter))

  (local-set-key (kbd "M-RET") (lambda () (interactive) (send-code-to-ghci-and-switch t)))

  (local-set-key (kbd "C-M-g") (lambda () (interactive) (send-code-to-ghci-and-switch nil))))

(add-hook 'haskell-mode-hook 'altech-define-haskell-hook)