Improvements to ratio_split()

damiendr commented 5 years ago

The current implementation of ratio_split() distributes any change left after rounding to the last participant.

This causes two minor issues:

participants with a ratio == 0 may still end up receiving change (debit or credit)
the distribution of change is not fair, eg. one participant may end up paying 0.03 more instead of having three participants pay 0.01 more.

This PR fixes this by using the Largest Remainder method to allocate change between participants with a ratio != 0.

It also fixes a further problem whereby ratio_split() assumed DECIMAL_PLACES=2.

coveralls commented 5 years ago

Coverage decreased (-0.05%) to 95.433% when pulling 92423c930d5e0cd8512ae7373ec3f6ceef9bb7fc on damiendr:better_ratio_split into 0ffcad1d3b388b860c8c47fde12aa40df213066f on adamcharnock:master.

adamcharnock commented 4 years ago

Hi @damiendr! Thank you for this, and sorry for taking so long to get back to you. I've merged this now and it should be released soon.

adamcharnock commented 4 years ago

Released in 1.10.0, which also drops support for Python 3.5 and includes #40

adamcharnock / django-hordak

Improvements to ratio_split() #38