15.2. Control Structures🔗

Normally, programs written in IO use the same control structures as those written in other monads. There is one specific IO helper.

opaque

IO.iterate {α β : Type} (a : α) (f : α → IO (α ⊕ β)) : IO β
IO.iterate {α β : Type} (a : α)
  (f : α → IO (α ⊕ β)) : IO β

Iterates an IO action. Starting with an initial state, the action is applied repeatedly until it returns a final value in Sum.inr. Each time it returns Sum.inl, the returned value is treated as a new state.