def foo (a : Array Nat) : Array Nat :=
let a := a.push 0
let a := a.push 1
let a := a.push 2
let a := a.push 3
a

def main : IO UInt32 := do
 let a : Array Nat := Array.empty
 IO.println (toString a)
 IO.println (toString a.sz)
 let a := foo a
 IO.println (toString a)
 let a := a.map (fun a => a + 10)
 IO.println (toString a)
 IO.println (toString a.sz)
 let a1 := a.pop
 let a2 := a.push 100
 IO.println (toString a1)
 IO.println (toString a2)
 let a2 := a.pop
 IO.println a2
 IO.println $ (([1, 2, 3, 4].toArray).map (fun a => a + 2)).map toString
 IO.println $ ([1, 2, 3, 4].toArray.extract 1 3)
 IO.println $ ([1, 2, 3, 4].toArray.extract 0 100)
 IO.println $ ([1, 2, 3, 4].toArray.extract 1 1)
 IO.println $ ([1, 2, 3, 4].toArray.extract 2 4)
 IO.println [1,2,3,4].toArray.reverse
 IO.println ([] : List Nat).toArray.reverse
 IO.println [1,2,3].toArray.reverse
 IO.println $ [1,2,3,4].toArray.filter (fun a => a % 2 == 0)
 IO.println $ [1,2,3,4,5].toArray.filter (fun a =>  a % 2 == 0)
 IO.println $ [1,2,3,4,5].toArray.filter (fun a => a % 2 == 1)
 IO.println $ [1,2,3,4].toArray.filter (fun a => a > 2)
 IO.println $ [1,2,3,4].toArray.filter (fun a => a > 10)
 IO.println $ [1,2,3,4].toArray.filter (fun a => a > 0)
 pure 0