Sum of Squares in F#: imperative, pure functional, native

sumOfSquares.fs

let sqr x = x * x

let sumOfSquaresI nums =
  let mutable acc = 0.0
  for x in nums do
    acc <- acc + sqr x
  acc

let rec sumOfSquaresF nums =
  match nums with
  | [] -> 0.0
  | head::tail -> sqr head + sumOfSquaresF tail

let sumOfSquares nums =
  nums
  |> Seq.map sqr
  |> Seq.sum