In the following code I am trying to set a mutable variable len to the length of a list.

How can I do this?

let DoPairs (dl:seq<myHash>) (cnt:int) :unit =

if cnt > 1 then

dl |> Seq.pairwise

|> Seq.iter (fun el -> Determine (fst el) (snd el))

InsertNs LastHash firstYr LastHash.yr

else

dl |> Seq.iter(fun mh -> InsertNs mh firstYr LastHash.yr)

let mutable len = 0

let grouping (data:seq<myHash>) :unit =

data |> Seq.toList

|> List.length (fun lstlen -> DoPairs data lstlen.Length)

DoPairs data len