Skip to content

QuantityPoint

QuantityPoint is our affine space type. The core use cases include:

  • Temperatures. Specifically, when you want to represent “what temperature is it?” rather than “how much did the temperature change?”

  • Mile markers. That is to say, points along a linear path which are indexed by distances. It wouldn’t make sense to add two mile markers, but you can subtract them and obtain a distance (which is a Quantity, not a QuantityPoint).

TODO: this page is a stub

We will provide a full-fledged reference for quantity points later. For now, here are the basics.

  1. QuantityPoint<U, R> stores a value of numeric type R (called the “Rep”), whose units are the unit type U.

    • Example: QuantityPoint<Meters, double> represents an along-path point, whose distance is measured in Meters, in a double variable.

  2. We provide “Rep-named aliases” for better ergonomics.

    • Example: QuantityPointD<Meters> is an alias for QuantityPoint<Meters, double>.

  3. You cannot get values into or out of QuantityPoint without explicitly naming the unit, at the callsite. We do not have tutorials for this yet, but it works the same as Quantity. In the meantime, you can read the QuantityPoint unit tests to see some practical examples.