Add a useful function

emacs/.emacs.d/init.org

@@ -896,6 +896,53 @@
             dired-subdir-switches "-Alh"))
   #+END_SRC
 
+* Useful functions
+
+  During your editing in Emacs you will undoubtedly find the need to
+  define your own editing functions or macros. Here are mine.
+
+** Delete the contents of the string at point
+
+   First we define the function. It was inspired by [[http://www.masteringemacs.org/][Mickey's post on
+   swapping quote symbols]], mostly copied even. First we check if we
+   are even in a string, and if not we throw an error, after that we
+   move back to the beginning of the string, store that point, go to
+   the end of the string (using =forward-sexp=) and then delete the
+   region between the two points (non-inclusive).
+
+   #+BEGIN_SRC emacs-lisp
+     (defun oni:delete-string-contents ()
+       (interactive)
+
+       (unless (in-string-p)
+         (error "You must be in a string for this command to work"))
+
+       (save-excursion
+         (while (in-string-p) (forward-char -1))
+
+         (let ((bos (point)))
+           (forward-sexp)
+           (delete-region (1+ bos) (1- (point))))))
+   #+END_SRC
+
+   Since for interactive functions it's kind of a pain to have to use
+   a personal "namespace" I prefer naming them regularly as if they're
+   just part of the environment. If ever Emacs comes up with a similar
+   function with the same name, I'd prefer using the built-in version.
+
+   #+BEGIN_SRC emacs-lisp
+     (unless (fboundp 'delete-string-contents)
+       (defalias 'delete-string-contents 'oni:delete-string-contents))
+   #+END_SRC
+
+   Lastly, any function worth using often should probably be easily
+   accessible with a keybinding. In my case the {{{key(C-c i s)}}} is
+   inspired by the Vim keybindings like {{{key(ci")}}}.
+
+   #+BEGIN_SRC emacs-lisp
+     (global-set-key (kbd "C-c i s") 'delete-string-contents)
+   #+END_SRC
+
 * Load custom file
 
   I don't really use the Emacs customization interface much, but I