LogBuilder Computation Expression

LogBuilder.fs

let logStep action =
    let res = action <| printf "%s... "
    printfn "Complete."
    res
type LoggingBuilder() =
    member this.Bind(x, f) =
        logStep x |> f
    member this.Zero() = ignore
    member this.Return(x) = x

let logBuilder = new LoggingBuilder()
let loggedAddxy x y logFn =
    logFn <| sprintf "Adding %d + %d" x y
    x + y
let loggedTupledAddxy (x,y) = loggedAddxy x y
let loggedNonIntThing () logFn =
    logFn <| sprintf "Logging a non-int thing"
    "hello"
let loggedWorkflow = 
    logBuilder {
        let! z = loggedAddxy 2 3
        let! w = loggedAddxy 8 z
        let! _text = loggedNonIntThing ()
        return w
    }
printfn "%d" loggedWorkflow