F# point free style division

Question

I'm looking for a way to do point-free style division. Point free style works great with most mathematical operators where the order of the arguments doesn't matter as in the case of multiplication, subtraction or addition.

But the problem is with division where I want to do div(x, y) but the order becomes div(y, x). As in this example:

let aList = [2;4;6;8]
let mut = aList |> List.map ((/)2)

The partially applied function becomes (fun x -> 2 / x). Which will yield [1; 0; 0; 0] while I would like it to be (fun x -> x / 2) -> [1; 2; 3; 4].

Is there any easy way to do this in a point free style?

Answer 1

Add a swap operator/function:

let swap f = fun x y -> f y x
let aList = [2;4;6;8]
let mut = aList |> List.map (swap (/) 2)

Answer 2

Use flip operator:

 let aList = [2;4;6;8]
 let (<.>) f a b = f b a
 let mut = aList |> List.map ((/) <.> 2)

Answer 3

I defined the MinusBy, DivBy, function:

/// Minus, easy for pipe forward
let inline MinusBy y x = x - y

/// Division, easy for pipe forward
let inline DivBy y x = x / y

How I find it useful in my statistics library:

// https://en.wikipedia.org/wiki/Normalization_(statistics)
let average = 2.0
let stdev = 3.0     // Standard Deviation
let Standardize (x:double) =
    x |> MinusBy average |> DivBy stdev

I got the idea from other users from my question:

F#, Pipe-forward first argument