Defining your own units

Package: UOM_PACKAGE. Registered by createEngine(); for a slimmer engine, register it explicitly (see choosing packages).

When the unit you want to work in is not one the engine ships, you can define it yourself in terms of one it does. A sprint is two weeks; a story point is four hours. Once named, it behaves like any built-in unit on the lines that follow.

A document can name a unit the engine does not ship, the same way it can define a function. Write 1 <name> = <quantity> <unit>, and the name works on every line below it.

1 sprint = 2 weeks // sprint defined
6 sprints in days // 84 days
1 story point = 4 hours // story point defined
13 story points // 52 hours

The base is always a real unit, so a defined unit inherits that unit’s dimension. 6 sprints in days converts, and 6 sprints in kg is refused the same way 2 weeks in kg is: a duration is not a mass.

Plurals and multi-word names both work, and only the natural 1 name = ... shape defines a unit, so 2 x = 10 is still an equation. A definition holds for the document that wrote it and nowhere else, and a later line redefining the same name replaces the earlier one.