tunes.pl

Introduction

Each time I enjoy some vacations with friends, there are many situations when someone needs to pay for the whole group, or even for a smaller group of persons. At the end of the holidays, everyone owes money to everyone... not much enjoyable to handle that by hand.

The program

Therefore I've written a Perl program, which takes a description file and computes out of it an efficient solving of owes.

Here's an example of a description file:

# -*- fundamental -*-

%group arrived-on-monday gc francois jacques
%group took-the-train gc phil

gc
	took-the-train    70.2 each      # train tickets
	307				 # food
	gc jacques        100            # first evening late night drinks

francois
	arrived-on-monday 170            # first evening restaurant

samuel

phil
	250				 # drink
   

As you can see, it's rather simple:

• each line may contain a # to indicate that the end of the line is a comment
• to declare amounts paid by a person, first put his name at the beginning of a line
• then, to specify what he/she paid, put a tab character, then either put the amount sole in line (indicates this was a payment for everyone), or first a list of person or a group name, then the amount; then, any option
• specify groups with the %group directive, as the example shows
• specify someone paying for someone else with the %payfor directive, for example %payfor pixel gc indicates that pixel will pay for gc (useful for couples or friends when someone has no money at the time)
• specify currencies with the %currency directive, for example %currency CHF 1.5 indicates that sums in CHF need to be divided by 1.5 to match the value of other sums (that would be the proper directive if other amounts are expressed in euros, since 1 euro equals 1.5 CHF)
• options are:
  • each: indicates that the amount is a per-person amount, not a global amount (global amounts are the default)
  • <currency>: indicates that the amount is expressed in the specified currency (this currency needs to be defined with the %currency directive)

Here's what the program gives:

Person gc:
        Paid in total:          547.40
        Owed to him/her total:  259.13
Person phil:
        Paid in total:          250.00
        Owed to him/her total:  150.00
        Owe to: gc               81.60
Person francois:
        Paid in total:          170.00
        Owed to him/her total:   56.67
        Owe to: phil             50.00
        Owe to: gc                4.73
Person jacques:
        Paid in total:            0.00
        Owed to him/her total:    0.00
        Owe to: phil             50.00
        Owe to: francois         56.67
        Owe to: gc              111.40
Person samuel:
        Paid in total:            0.00
        Owed to him/her total:    0.00
        Owe to: phil             50.00
        Owe to: gc               61.40

Proposed owes solving:
        jacques      gives  218.07 to gc 
        samuel       gives   68.40 to phil 
        samuel       gives   41.07 to gc 
        samuel       gives    1.93 to francois 
   

Download the program: tunes.pl.