(* fn is a function which specifies how to join an item from list a to an item from list b *)
    let rec outerProduct fn a b =
        b |> List.collect (function h -> List.map (fn h) a)

// And this is a sample of how I used this:

type Name = { FirstName:string; LastName:string; Age:int}

// makeName gets successively curried down the pipeline, until it finally generates the record at then end
let makeName a b c = { FirstName = a; LastName = b; Age = c}

let l1 = 
    ["bill"; "Fred"; "James"]  
    |> List.map (fun x -> makeName x) 
    |> outerProduct (fun f p -> f p) ["Smith"; "Jones"]
    |> outerProduct (fun f p -> f p) [21; 22]

(* This produces the output:
 [
    {FirstName = "bill"; LastName = "Smith"; Age = 21;}; 
    {FirstName = "bill"; LastName = "Smith"; Age = 22;}; 
    {FirstName = "bill"; LastName = "Jones"; Age = 21;}; 
    {FirstName = "bill"; LastName = "Jones"; Age = 22;}; 
    {FirstName = "Fred"; LastName = "Smith"; Age = 21;};
    {FirstName = "Fred";LastName = "Smith";Age = 22;}; 
    {FirstName = "Fred";LastName = "Jones";Age = 21;}; 
    {FirstName = "Fred"; LastName = "Jones"; Age = 22;}; 
    {FirstName = "James"; LastName = "Smith"; Age = 21;}; 
    {FirstName = "James"; LastName = "Smith"; Age = 22;};
    {FirstName = "James";LastName = "Jones";Age = 21;}; 
    {FirstName = "James";LastName = "Jones";Age = 22;}
 ]

*)