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POUnits of measure in C# - almost
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  1. POUnits of measure in C# - almost
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    copied!<p>Inspired by <a href="https://stackoverflow.com/questions/40845/how-do-f-units-of-measurement-work">Units of Measure in F#</a>, and despite asserting (<a href="https://stackoverflow.com/questions/39492/where-can-f-actually-save-time-and-money#71112">here</a>) that you couldn't do it in C#, I had an idea the other day which I've been playing around with.</p> <pre><code>namespace UnitsOfMeasure { public interface IUnit { } public static class Length { public interface ILength : IUnit { } public class m : ILength { } public class mm : ILength { } public class ft : ILength { } } public class Mass { public interface IMass : IUnit { } public class kg : IMass { } public class g : IMass { } public class lb : IMass { } } public class UnitDouble&lt;T&gt; where T : IUnit { public readonly double Value; public UnitDouble(double value) { Value = value; } public static UnitDouble&lt;T&gt; operator +(UnitDouble&lt;T&gt; first, UnitDouble&lt;T&gt; second) { return new UnitDouble&lt;T&gt;(first.Value + second.Value); } //TODO: minus operator/equality } } </code></pre> <p>Example usage:</p> <pre><code>var a = new UnitDouble&lt;Length.m&gt;(3.1); var b = new UnitDouble&lt;Length.m&gt;(4.9); var d = new UnitDouble&lt;Mass.kg&gt;(3.4); Console.WriteLine((a + b).Value); //Console.WriteLine((a + c).Value); &lt;-- Compiler says no </code></pre> <p>The next step is trying to implement conversions (snippet):</p> <pre><code>public interface IUnit { double toBase { get; } } public static class Length { public interface ILength : IUnit { } public class m : ILength { public double toBase { get { return 1.0;} } } public class mm : ILength { public double toBase { get { return 1000.0; } } } public class ft : ILength { public double toBase { get { return 0.3048; } } } public static UnitDouble&lt;R&gt; Convert&lt;T, R&gt;(UnitDouble&lt;T&gt; input) where T : ILength, new() where R : ILength, new() { double mult = (new T() as IUnit).toBase; double div = (new R() as IUnit).toBase; return new UnitDouble&lt;R&gt;(input.Value * mult / div); } } </code></pre> <p>(I would have liked to avoid instantiating objects by using static, but as we all know you <a href="https://stackoverflow.com/questions/259026/why-doesnt-c-allow-static-methods-to-implement-an-interface">can't declare a static method in an interface</a>) You can then do this:</p> <pre><code>var e = Length.Convert&lt;Length.mm, Length.m&gt;(c); var f = Length.Convert&lt;Length.mm, Mass.kg&gt;(d); &lt;-- but not this </code></pre> <p>Obviously, there is a gaping hole in this, compared to F# Units of measure (I'll let you work it out).</p> <p>Oh, the question is: what do you think of this? Is it worth using? Has someone else already done better?</p> <p><strong>UPDATE</strong> for people interested in this subject area, <a href="http://www.cs.utexas.edu/users/novak/units95.pdf" rel="nofollow noreferrer">here</a> is a link to a paper from 1997 discussing a different kind of solution (not specifically for C#)</p>
 

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