This repository contains a Ruby implementation of measurements based on the article Arithmetic with Measurements on Dynamically-Typed Object-Oriented Languages.
The library is not intended for production use.
Usage
Firstly, you should define desired units and their relationships. For example:
@kg = BaseUnit.new('kg')
@m = BaseUnit.new('m')
@km = ProportionalDerivedUnit.new('km', 1000, @m)
@s = BaseUnit.new('s')Secondly, measurements should be created by calling
Measurement.new(amount, unit). The objects support four basic arithmetic
operations and handle unit compatibility and conversions, e.g.:
t = Measurement.new(10, @s)
x = Measurement.new(3.3, @km)
v = x / t # = 330.0 m / sDifferences from the Paper
Firstly, MeasurementBag and NonProportionalDerivedUnit haven't been
implemented yet.
Secondly, units are not simplified, i.e. km * h / h will not yield km. The only type of simplification that is performed is when both the numerator and denominator contain exactly the same units in the same order.
Thirdly, multiplication of units is non-commutative. Subtracting 2 m * s from 10 s * m should yield 8 m * s = 8 s * m. It fails in the current version.
Design Limitations
The library assumes one-way conversion - from a derived to base unit. The goal is having the ability to compute and compare measurements of different but related units. The conversion in the other direction is not supported.
Another limitation, which may not be present in the library presented in the paper, is that unit conversion is performed even when it isn't strictly necessary. Dividing 3.3 km by 10 s yields, as demonstrated by the example above, 330 m / s instead of 0.33 km / s.