// For more information see https://aka.ms/fsharp-console-apps
printfn "Hello from F#"

// printfn "%A" ((fun x -> x+1)3)

let ratio(x,y) =
  let z = x * y
  let w = 2 * (x + y)
  w / z

let ratio2(x : float, y : float) =
  let z = x * y
  let w = ((2 : float) * x) + ((2 : float) * y)
  w / z

printfn "%A" (ratio2(2.1,3.0))

let getType(x) = x.GetType().FullName

let rec Fib (n : int) =
  if (n = 0 || n = 1) then 1
  else Fib (n - 1) + Fib (n - 2)

let TrNum (n : int) = n*(n+1)/2

printfn "%A" (TrNum(10))

let rec ProdNum (n : int) =
  match n with
  | 1 -> 1
  | _ -> ProdNum(n-1)*n

let rec sumFirstFun f k =
  if k<=0 then 0 else f k + sumFirstFun f (k-1)

let rec fold g f k1 k2 z =
  if (k2 < k1) then z
  else g (fold g f (k1+1) k2 z) (f(k1))

let sum x y = x + y
let double x = 2*x

printfn "%A" (fold sum double 10 100 0)

printfn "%A" (ProdNum(5))

printfn "%A" (Fib (5))