Units of measure in F#

To define a unit of measure in F#, you need to add the [] attribute before a type declaration.

You can then qualify an appropriate numeric value with a unit of measure (by enclosing it within <..>) so that it will only work with that particular unit of measure. For example:

[]

type celsius

let printTemperature(temp : float) =   // temp must be a float with unit of measure 'celsius'

     if temp = -273.15<_> then

        printfn "Absolute zero"

     elif temp < 0.0<_> then

        printfn "Below freezing"

     elif temp = 0.0<_> then

        printfn "Freezing point"

     elif temp < 100.0<_> then

        printfn "Above freezing"

     elif temp = 100.0<_> then

        printfn "Boiling point"

     else

        printfn "Above boiling"  

let temp = 30.0

printTemperature temp  // Above freezing

let temp2 = -273.15

printTemperature temp2  // Absolute zero