vvvv gamma

// vvvv gamma (VL) - Fibonacci Sequence
// Visual Language patch demonstrating recursive operations and stateful processes

// A record type holding memoized Fibonacci results
record FibState
  Previous : Integer32 = 0
  Current  : Integer32 = 1
  Count    : Integer32 = 0

// Advance to the next Fibonacci number (stateful step)
operation Step (State : FibState) : (Value : Integer32) (State : FibState)
  Value = State.Current
  State = FibState(
    Previous = State.Current,
    Current  = State.Previous + State.Current,
    Count    = State.Count + 1
  )

// Compute the nth Fibonacci number iteratively via repeated Step
operation Fibonacci (N : Integer32) : (Result : Integer32)
  let mutable state = FibState()
  let mutable result = 0
  for i = 0 to N - 1 do
    let (v, s) = Step(state)
    result <- v
    state  <- s
  Result = result

// Entry point: print the first 10 Fibonacci numbers
operation Main () : Unit
  for i = 0 to 9 do
    let fib = Fibonacci(i)
    Console.WriteLine($"Fibonacci({i}) = {fib}")