import std.io;
import std.time;
import std.value;

func benchmark(fn: Function, arg: Any) -> Null
{
    io.println("Testing fn:", fn, "with arg:", arg);
    const start := time.now();
    
    const result := fn(arg);
    
    const end := time.now();
    const duration := new time.Time{
        end.since(start)
    };
    io.println("=" * 50);
    io.println("fn returns:", result, "\n");
    io.println("Cost:", duration.toSeconds(), "s");
    io.println("     ", duration.toMillis(), "ms");
}

var memo := {};

func fib_memo(x)
{
    if memo.contains(x)
    {
        return memo.get(x);
    }
    if x <= 1
    {
        memo[x] = x;
        return x;
    }
    var result := fib_memo(x - 1) + fib_memo(x - 2);
    memo[x] = result;
    return result;
}

func fib_iter(n)
{
    var a := 0;
    var b := 1;
    for var i := 0; i < n; i = i + 1
    {
        var temp := a + b;
        a = b;
        b = temp;
    }
    return a;
}

func fib(x)
{
    if x <= 1
    {
        return x;
    }
    return fib(x - 1) + fib(x - 2);
}

func fib_tail(n, a=0, b=1) {
    if n == 0 { return a; }
    if n == 1 { return b; }
    return fib_tail(n-1, b, a+b);
}

const n := 30;

io.println("! fib(" + value.string_from(n) + "):");
benchmark(fib, n);
io.print("\n\n");

io.println("! fib_memo(" + value.string_from(n) + "):");
benchmark(fib_memo, n);
io.print("\n\n");

io.println("! fib_iter(" + value.string_from(n) + "):");
benchmark(fib_iter, n);
io.print("\n\n");

io.println("! fib_tail(" + value.string_from(n) + "):");
benchmark(fib_tail, n);
io.print("\n\n");