

Units of Measure in F#: Part One, Introducing Units - strlen
http://blogs.msdn.com/b/andrewkennedy/archive/2008/08/29/units-of-measure-in-f-part-one-introducing-units.aspx

======
equark
Units of measure has always struck me as a pet feature of F# that's only there
because it happened to be what somebody's PhD dissertation was written on.
Whether it is useful in practice is unclear.

I saw Don Syme give a presentation where he tried to add twice the variance to
the mean of a variable. This is actually perfectly sensible to do -- it's some
quantile point. But it gives a type error since variance has units squared in
it. So he took the square root to solve the "problem." Obviously it was just a
demo, but he claimed the the Microsoft Ad team had similar bugs confusing the
variance and standard deviation. I can almost imagine some code maintenance
guy adding units of measure and thinking there's a bug in some carefully
constructed algorithm when in fact there is not.

All sorts of statistics have this issue.

