# UnitOps

UnitOps are the "arithmetic" operations on units, used for actions like withdrawing a payment from a purse. All of the custom behavior is stored in the ExtentOps, allowing for UnitOps to be polymorphic, exposing the same interface while allowing custom behavior.

# Types of UnitOps

# UniUnitOps

UniUnitOps represents units that have unique descriptions. It is a refinement of UnitOps that we've found useful, but has no special place in the protocol.

The extent must either be null, in which case it is empty, or be some truthy comparable value, in which case it represents a single unique unit described by that truthy extent. Combining two uni units with different truthy extents fails, as they represent non-combinable rights.

# NatUnitOps

UnitOps for a labeled natural number describing a extent of fungible erights. The label describes what kinds of rights these are. NatUnitOps is a refinement of UnitOps that we've found useful, but has no special place in the protocol.

Empty units have an extent equal to 0. includes() verifies that leftUnits is greater than or equal to rightUnits. with() and without() add and subtract their contents.