> They are binary relations, Thanks for making my point: this API provides _a_ binary relation is IMO useless. There are millions of binary relations that one

> They are binary relations, Thanks for making my point: this API provides _a_ binary relation is IMO useless. There are millions of binary relations that one could implement for a type, and often many that make sense implementing for a particular type, and that this API doesn't support (e.g. there are both strict partial order and total orders for float in the IEEE standard; this API however implements none). For this to be useful, the docs would at least need to say what can one assume about the partial order implemented by PartialOrd (is it strict? is it non-strict? something else?), and ideally have a solid ordering hierarchy so that APIs and algorithms can pick what makes sense to them, instead of having to assume the lowest-possible denominator imaginable, which results in, e.g., it not making sense to implement ordering for floats in the standard library, even though to be IEEE compliant it would actually need to do that.