<p>I was reading Andrew Kennedy's blog post series on <a href="http://blogs.msdn.com/andrewkennedy/archive/2008/08/29/units-of-measure-in-f-part-one-introducing-units.aspx" rel="noreferrer">units of measurement in F#</a> and it makes a lot of sense in a lot of cases.  Are there any other languages that have such a system?</p>

<p>Edit: To be more clear, I mean the flexible units of measurement system where you can define your own arbitrarily.</p>

I'm not sure if this really counts, but the
```
RPL
```
system on my HP-48 calculator does have similar features. I can write
```
40_gal 5_l +
```
and get the right answer of  156.416 liters.