For someone who studied accounting, I've never really paid a huge amount
of attention to where my money goes when I stop looking. Generally
speaking, as long as I've got somewhere to live and a steady supply of
cheese and wine I'm not too worried.

So it's funny that I suddenly decided that it would be a good idea to
track my expenses, but there you have it. I thought I'd write a little
Clojure program that would let me enter my recurring and one-off
expenses (in a format reminiscent of Emacs's ~/.diary file) and have it
tell me where all my money got to each week.

To compile it:

  1.  Get Leiningen from http://github.com/technomancy/leiningen and put
      the 'lein' script somewhere in your $PATH.

  2.  Run `lein uberjar'.  Lein will grab all required dependencies and
      produce a `expenses.jar'.

To use it, I create a file called ~/.expenses that looks roughly like
this:

  ## Recurring stuff...
  #

  # This is the default anyway, but you can set the reported week to
  # start whenever you like.
  #set week_start Sunday

  # Amounts we receive are entered as negative numbers...
  fortnightly     -10000  Fortnightly pay (I wish)
  weekly          345.5   Rent (also optimistic)
  monthly         123     Internet+phone

  # Recurring items can have ranges attached to let you reflect changes
  # in amounts over time, etc.
  [--1/3/2009]    monthly         123  Health cover
  [1/3/2009--]    monthly         234  Health cover (the bastards!)

  fortnightly     50      Petrol
  yearly          2345    Gas & Electricity
  yearly          700     Car registration

  # etc...

  # One-off expenditures
  #
  25/02/2009      11.00   Coffee
  25/02/2009      9.50    Lunch      (some extra (ignored) notes here)
  25/02/2009      25.00   Wine
  26/02/2009      25.00   Wine
  27/02/2009      25.00   Wine
  # ... more wine...

Then I point the expenses program at this file to see the report over
time:

$ java -jar expenses.jar ~/.expenses


  ======================================================
  Week starting: Sun Feb 22 00:00:00 EST 2009
  ======================================================

    Recurring items:

      22/02/2009          Fortnightly pay (I wish)                 5000.00
      22/02/2009          Rent (also optimistic)                  ( 345.50)
      22/02/2009          Internet+phone                          (  30.75)
      22/02/2009          Health cover                            (  30.75)
      22/02/2009          Petrol                                  (  25.00)
      22/02/2009          Gas & Electricity                       (  45.10)
      22/02/2009          Car registration                        (  13.46)

      Subtotal:                                                     4509.44

    Line items:

      25/02/2009          Coffee                                  (  11.00)
      25/02/2009          Lunch                                   (   9.50)
      25/02/2009          Wine                                    (  25.00)
      26/02/2009          Wine                                    (  25.00)
      27/02/2009          Wine                                    (  25.00)

      Subtotal:                                                   (  95.50)

    =========================
     Total saved: 4413.94
    =========================

Hooray! I'm fictitiously rich!

And that's basically all it does: it apportions recurring expenses over
each week so you can get a more realistic idea of what they cost you
week-to-week, and makes it easy to record one-off items too. For
recording those one-offs I use a snippet of Emacs lisp which I bind to a
key:

  (defun spend ()
    (interactive)
    (let ((now (time-stamp-dd/mm/yyyy))
          (amount (read-number "Amount: "))
          (description (read-string "Description?: ")))
      (with-current-buffer (find-file-noselect "~/.expenses")
        (goto-char (point-max))
        (insert (format "%s\t%.2f\t%s\n"
                        now
                        amount
                        description))
        (save-buffer)
        (kill-buffer))))