lifepillar/ledger-web — comment on commit e249d35ade06c365625551aa8cebf7fda0004769
File:  line 0
By lifepillar:

'NaN' is a special numeric value (http://www.postgresql.org/docs/9.1/static/datatype-numeric.html), so the code is syntactically correct. Besides, I think it makes the most sense, as the derivative of (i-e)/i goes to infinity as i approaches zero.