Managing my expenses using Clojure

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.

You can see my source code or download the self-contained jar file to try for yourself.

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

## Recurring stuff...
#

# 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
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))))