When I write a library that’s going to be used by others, I strive for a gentle learning curve. When someone reads code that uses my library, I want them to understand what’s happening without reading a bunch of documentation first. I tend to keep my API’s as explicit as possible, and try to stay away from odd or foreign notations.
My colleague Brent is writing a library to deal with date & time periods in PHP. There was a discussion whether a period’s boundaries should be included in the range or not.