purescript-units

Purescript types and functions for managing units of measure at runtime.

The API and implementation are currently experimental, subject to change, and open to suggestion.

Motivation

Adding 4 meters to 2 seconds doesn't make sense but is easy to do by mistake when both quantities are represented by simple Numbers. For correct implementation, understanding both a value and its significance is essential.

Functionality

This library provides functionality for performing mathematical operations and tracking the dimensionality of results along the way. Any operation that does not make sense dimensionally returns an error type that is propagated through subsequent operations. Conversion between units of the same dimensionality is easy.

This library provides two pieces of functionality.

1. Data.Units.Core defines types and functions for defining Dimensions and Quantities that represent values in those Dimensions. For example, time is a Dimension, and 1 second is a Quantity of time. The functionality included in this module is general and allows the user to define his or her own dimension sets, do math and unit conversion with them, and examine results. For example, possible dimensions could include sales, points, coverage area, reviews, etc.
2. Data.Units.Physical.SI uses the functionalty in Data.Units.Core to define the SI set of dimensions (length, time, amount, current, mass, temperature, and luminous intensity) as well as the standard units of each (meter, second, mol, etc.).

Future additions include more physical units and possibly additional dimension standards.

Usage

Example usage is provided in the test directory.