let accuracy = 0.00001

let rec iterate x a =
    let diff = x - a*a
    if abs diff <= accuracy then
        a
    else
        iterate x ((a + x/a) / 2.0)

let newtonSqrt x =
    iterate x (x/2.0)

let squared = 10.0
printfn "square root of %A = %A" squared (newtonSqrt squared)