F# Spec

This might be in one of the books on F# floating about, but if it is I never noticed it.

This example is copied from the F# spec

[<Measure>] type kg 
[<Measure>] type m 
[<Measure>] type s 
let gravityOnEarth = 9.81<m/s^2>
let heightOfTowerOfPisa = 55.86<m> 
let speedOfImpact = sqrt(2.0 * gravityOnEarth * heightOfTowerOfPisa)

 So what is so exciting about this? It’s not that you have set units on the first two values, it’s that F# works out the units of the last calculation:

val speedOfImpact : float<m/s> = 33.10548595

 How cool is that?

And it checks the units in calculations – so you can’t add a length to a weight if the values have suitable units… YO!