FSharp.UMX

F# Units of Measure for primitive non-numeric types by Eirik Tsarpalis. Compatible with Fable.

Installing

Add the FSharp.UMX package from Nuget or just copy the src/FSharp.UMX.fs file.

Publishing to Nuget

Run npm i && npm run build publish.

Usage

open FSharp.UMX

[<Measure>] type customerId
[<Measure>] type orderId
[<Measure>] type kg

type Order =
    {
        id : string<orderId>
        customer : string<customerId>
        quantity : int<kg>
    }

let order =
    {
        id = % "orderId"
        customer = % "customerId"
        quantity = % 42
    }

let printOrder (order : Order) =
    printfn "orderId=%s customerId=%s quantity=%d" %order.id %order.customer %order.quantity

let lookupById (orders : Order list) (id : string<orderId>) = orders |> List.tryFind (fun o -> o.id = id)

lookupById [] order.id // compiles
lookupById [] order.customer // compiler error
// stdin(94,15): error FS0001: Type mismatch. Expecting a
//     'string<orderId>'
// but given a
//     'string<customerId>'
// The unit of measure 'orderId' does not match the unit of measure 'customerId'

Example in Fable REPL