{-
Transform the value in an `Optional` into `Text`, defaulting `None` to `""`
-}
let defaultMap
    : ∀(a : Type) → (a → Text) → Optional a → Text
    =   λ(a : Type)
      → λ(f : a → Text)
      → λ(o : Optional a)
      → merge { Some = f, None = "" } o

let example0 = assert : defaultMap Natural Natural/show (Some 0) ≡ "0"

let example1 = assert : defaultMap Natural Natural/show (None Natural) ≡ ""

in  defaultMap