data Nat : Type where
  Z : Nat
  S : Nat -> Nat

data NotZero : Nat -> Type where
  Is : {n : Nat} -> NotZero (S n)

record Positive (n : Nat) {auto 0 pos : NotZero n} where
  constructor Check

a : Positive (S Z)
a = Check

b : Positive (S (S Z))
b = Check


data KindOfString : Type where
 ASCII : KindOfString
 UTF   : KindOfString

UTForASCII : KindOfString -> Type
UTForASCII UTF = String
UTForASCII ASCII = Nat   -- Just as demonstration

record FlexiString { default UTF k : KindOfString} where
  constructor MkFlexiString
  val : UTForASCII k
  
c : FlexiString
c = MkFlexiString "hello"

d : FlexiString {k = ASCII}
d = MkFlexiString Z