Implementations of fold and reduce functions in F#

fold-reduce.fsx

let rec fold f state list =
  match list with
    | [] -> state
    | head::rest -> fold f (f state head) rest

let reduce f list =
  match list with
    | [] -> invalidArg "list" "Cannot pass an empty list"
    | head::rest -> fold f head rest

let concat = sprintf "%s%s"
let strs = ["Example"; "Strings"; "To"; "Join"]

printfn "%s" <| reduce concat strs
printfn "%s" <| fold concat System.String.Empty strs