Learning emacs - programming emacs with elisp - I

I'm learning emacs and wanted to blog about how to script it and make it do things to enhance your productivity. The stuff I'm going to do here is really one step up from being a reasonably proficient user of emacs if that. I'm really only just getting used to lisp and emacs version of it — called elisp.

There is an opportunity here, though. By getting to know emacs better you will have to learn elisp. And by learning elisp, you are really learning a fully-capable programming language and a dialect of lisp. So you get to kill 2 birds with one stone: you get to know one of the most extensible text editors and one of the most extensible programming languages - it's no coincidence the two are related.

Warm up - evaluating some elisp

• If you're new to emacs, see this link: Getting help in emacs
• Load up emacs
• head over to the *scratch* buffer
• Let's look at one of the most basic operations in emacs: moving the cursor forward. How do we find what function is involved? Type: C-h k C-f . "C-h k" invokes the help function in emacs that is responsible for telling you what a key combination does; the key combination we asked it to look up was "C-f" - which is emacs default way to move the cursor forward. On my emacs, this is bound to "(forward-char &optional n)"[1]. What this means is that it is bound to the function "forward-char" which takes an optional argument "n".
• So, on a new line in *scratch* type: (forward-char 2) 1234567890 Leave no spaces between your text and the left edge of the buffer.
• Now put your cursor right at the end of the line with forward-char: ("|" is the position of the cursor below)

              (forward-char 2)|
              1234567890
            

  ... and type C-x C-e
  You cursor should move to here:

              (forward-char 2)
              1|234567890
            

  Try changing 2 to 1 or -1 and see what happens.
  NOTE: always put your cursor right to the end of the line before you type C-x C-e. One easy way to do this is to type C-e before you type C-x C-e
• What you've done is execute your first lisp program.
• Another way you could have executed 'forward-char' is via emacs' M-x key; type M-x forward-char and press RETURN and follow the prompts.
• What you should note is that any function that we run in emacs can be called using S-expressions (using lisp-parlance). Something like this

              (some-function arg1 arg2 ...)
            

  Which in more "mainstream" languages would look more like:

              some_function(arg1,arg2,...)
            

  This is how lisp and scheme work in general. The reasons for surrounding things in brackets runs quite deep. If you want to get into it, google "cons cell", "homoiconic" or just "lisp". For my purposes I'm just showing how to get started programmatically in emacs in this article.

Here's a great little series on lisp programming by James Turner. There are at least 4 parts.

[1] - if you are in viper-mode, you should go into insert mode (press i) and use the emacs key bindings to move around eg C-e and C-x C-e will work in insert mode (my viper experience level is set to 5 so your mileage may vary if you are using a lower level).