F# - cross product of two lists
*Messing around with 'extension functions' for the List module. (I spent quite a while developing 'mapfold' - which threads an accumulator like fold, but uses it as a parameter to create new values like map - then discovered that that is what List.scan_left does)*

For generation of test data, I needed to do a cross product of two lists, This is what I came up with:

    ///Perform cross product of two lists, return tuple
    let crossproduct l1 l2 =
        let product lst v2 = List.map (fun v1 -> (v1, v2)) lst
        List.map_concat (product l1) l2

Is this any good, or is there already some better way to do this?

Same question for this one:

    ///Perform cross product of three lists, return tuple
    let crossproduct3 l1 l2 l3 =
        let tuplelist = crossproduct l1 l2 //not sure this is the best way...
        let product3 lst2 v3 = List.map (fun (v1, v2) -> (v1, v2, v3)) lst2
        List.map_concat (product3 tuplelist) l3
F# - cross product of two lists
===

*Messing around with 'extension functions' for the List module. (I spent quite a while developing 'mapfold' - which threads an accumulator like fold, but uses it as a parameter to create new values like map - then discovered that that is what List.scan_left does)*

For generation of test data, I needed to do a cross product of two lists, This is what I came up with:

    ///Perform cross product of two lists, return tuple
    let crossproduct l1 l2 =
        let product lst v2 = List.map (fun v1 -> (v1, v2)) lst
        List.map_concat (product l1) l2

Is this any good, or is there already some better way to do this?

Same question for this one:

    ///Perform cross product of three lists, return tuple
    let crossproduct3 l1 l2 l3 =
        let tuplelist = crossproduct l1 l2 //not sure this is the best way...
        let product3 lst2 v3 = List.map (fun (v1, v2) -> (v1, v2, v3)) lst2
        List.map_concat (product3 tuplelist) l3