does a tee function exist somewhere in F# library?

Question

...or in FSharpx?

let tee sideEffect =
    fun x ->
        do sideEffect x
        x

The usage could be something like

f >> tee (printfn "F returned: %A") >> g >> h

Or is there another simple way to do this?

thanks!

Answer 1

ExtCore includes a function called tap which does exactly what you want. I use it for primarily for inspecting intermediate values within an F# "pipeline" (hence the name).

For example:

[| 1;2;3 |]
|> Array.map (fun x -> x * 2)
|> tap (fun arr ->
    printfn "The mapped array values are: %A" arr)
|> doOtherStuffWithArray

Answer 2

The closest I've seen is actually in WebSharper. The definition is:

let inline ( |>! ) x sideEffect =
    do sideEffect x
    x

Usage:

(x |>! printf "%A") |> nextFunc