Starter Kit Defuns

(defun view-url ()
  "Open a new buffer containing the contents of URL."
  (interactive)
  (let* ((default (thing-at-point-url-at-point))
         (url (read-from-minibuffer "URL: " default)))
    (switch-to-buffer (url-retrieve-synchronously url))
    (rename-buffer url t)
    (cond ((search-forward "<?xml" nil t) (xml-mode))
          ((search-forward "<html" nil t) (html-mode)))))

(defun ido-imenu ()
  "Update the imenu index and then use ido to select a symbol to navigate to.
Symbols matching the text at point are put first in the completion list."
  (interactive)
  (imenu--make-index-alist)
  (let ((name-and-pos '())
        (symbol-names '()))
    (flet ((addsymbols (symbol-list)
                       (when (listp symbol-list)
                         (dolist (symbol symbol-list)
                           (let ((name nil) (position nil))
                             (cond
                              ((and (listp symbol) (imenu--subalist-p symbol))
                               (addsymbols symbol))
                              
                              ((listp symbol)
                               (setq name (car symbol))
                               (setq position (cdr symbol)))
                              
                              ((stringp symbol)
                               (setq name symbol)
                               (setq position (get-text-property 1 'org-imenu-marker symbol))))
                             
                             (unless (or (null position) (null name))
                               (add-to-list 'symbol-names name)
                               (add-to-list 'name-and-pos (cons name position))))))))
      (addsymbols imenu--index-alist))
    ;; If there are matching symbols at point, put them at the beginning of `symbol-names'.
    (let ((symbol-at-point (thing-at-point 'symbol)))
      (when symbol-at-point
        (let* ((regexp (concat (regexp-quote symbol-at-point) "$"))
               (matching-symbols (delq nil (mapcar (lambda (symbol)
                                                     (if (string-match regexp symbol) symbol))
                                                   symbol-names))))
          (when matching-symbols
            (sort matching-symbols (lambda (a b) (> (length a) (length b))))
            (mapc (lambda (symbol) (setq symbol-names (cons symbol (delete symbol symbol-names))))
                  matching-symbols)))))
    (let* ((selected-symbol (ido-completing-read "Symbol? " symbol-names))
           (position (cdr (assoc selected-symbol name-and-pos))))
      (goto-char position))))

We have a number of turn-on-* functions since it's advised that lambda functions not go in hooks. Repeatedly evaling an add-to-list with a hook value will repeatedly add it since there's no way to ensure that a lambda doesn't already exist in the list.

(defun local-column-number-mode ()
  (make-local-variable 'column-number-mode)
  (column-number-mode t))

(defun local-comment-auto-fill ()
  (set (make-local-variable 'comment-auto-fill-only-comments) t)
  (auto-fill-mode t))

(defun turn-on-hl-line-mode ()
  (if window-system (hl-line-mode t)))

(defun turn-on-save-place-mode ()
  (setq save-place t))

(defun turn-on-whitespace ()
  (whitespace-mode t))

(add-hook 'coding-hook 'local-column-number-mode)

(add-hook 'coding-hook 'local-comment-auto-fill)

(add-hook 'coding-hook 'turn-on-hl-line-mode)

(add-hook 'coding-hook 'pretty-lambdas)

(defun run-coding-hook ()
  "Enable things that are convenient across all coding buffers."
  (run-hooks 'coding-hook))

(defun untabify-buffer ()
  (interactive)
  (untabify (point-min) (point-max)))

(defun indent-buffer ()
  (interactive)
  (indent-region (point-min) (point-max)))

(defun cleanup-buffer ()
  "Perform a bunch of operations on the whitespace content of a buffer."
  (interactive)
  (indent-buffer)
  (untabify-buffer)
  (delete-trailing-whitespace))

(defun recentf-ido-find-file ()
  "Find a recent file using ido."
  (interactive)
  (let ((file (ido-completing-read "Choose recent file: " recentf-list nil t)))
    (when file
      (find-file file))))

(defun pretty-lambdas ()
  (font-lock-add-keywords
   nil `(("(?\\(lambda\\>\\)"
          (0 (progn (compose-region (match-beginning 1) (match-end 1)
                                    ,(make-char 'greek-iso8859-7 107))
                    nil))))))

(defun eval-and-replace ()
  "Replace the preceding sexp with its value."
  (interactive)
  (backward-kill-sexp)
  (condition-case nil
      (prin1 (eval (read (current-kill 0)))
             (current-buffer))
    (error (message "Invalid expression")
           (insert (current-kill 0)))))

(defun recompile-init ()
  "Byte-compile all your dotfiles again."
  (interactive)
  (byte-recompile-directory dotfiles-dir 0)
  ;; TODO: remove elpa-to-submit once everything's submitted.
  (byte-recompile-directory (concat dotfiles-dir "elpa-to-submit/" 0)))

(defun regen-autoloads (&optional force-regen)
  "Regenerate the autoload definitions file if necessary and load it."
  (interactive "P")
  (let ((autoload-dir (concat dotfiles-dir "/elpa-to-submit"))
        (generated-autoload-file autoload-file))
    (when (or force-regen
              (not (file-exists-p autoload-file))
              (some (lambda (f) (file-newer-than-file-p f autoload-file))
                    (directory-files autoload-dir t "\\.el$")))
      (message "Updating autoloads...")
      (let (emacs-lisp-mode-hook)
        (update-directory-autoloads autoload-dir))))
  (load autoload-file))

TODO: fix this

(defun sudo-edit (&optional arg)
  (interactive "p")
  (if arg
      (find-file (concat "/sudo:root@localhost:" (ido-read-file-name "File: ")))
    (find-alternate-file (concat "/sudo:root@localhost:" buffer-file-name))))

Useful when a large block of text is required (e.g. for testing)

(defun lorem ()
  "Insert a lorem ipsum."
  (interactive)
  (insert "Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do "
          "eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim"
          "ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut "
          "aliquip ex ea commodo consequat. Duis aute irure dolor in "
          "reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla "
          "pariatur. Excepteur sint occaecat cupidatat non proident, sunt in "
          "culpa qui officia deserunt mollit anim id est laborum."))

(defun switch-or-start (function buffer)
  "If the buffer is current, bury it, otherwise invoke the function."
  (if (equal (buffer-name (current-buffer)) buffer)
      (bury-buffer)
    (if (get-buffer buffer)
        (switch-to-buffer buffer)
      (funcall function))))

(defun insert-date ()
  "Insert a time-stamp according to locale's date and time format."
  (interactive)
  (insert (format-time-string "%c" (current-time))))

(defun pairing-bot ()
  "If you can't pair program with a human, use this instead."
  (interactive)
  (message (if (y-or-n-p "Do you have a test for that? ") "Good." "Bad!")))

A monkeypatch to cause annotate to ignore whitespace

(defun vc-git-annotate-command (file buf &optional rev)
  (let ((name (file-relative-name file)))
    (vc-git-command buf 0 name "blame" "-w" rev)))