/Prelude-v21.1.0/Optional/map.dhall

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Transform an Optional value with a function

Examples

map Natural Bool Natural/even (Some 3) ≡ Some False
map Natural Bool Natural/even (None Natural) ≡ None Bool

Source

--| Transform an `Optional` value with a function
let map
: ∀(a : Type) → ∀(b : Type) → (a → b) → Optional a → Optional b
= λ(a : Type) →
λ(b : Type) →
λ(f : ab) →
λ(o : Optional a) →
merge { Some = λ(x : a) → Some (f x), None = None b } o

let example0 = assert : map Natural Bool Natural/even (Some 3) ≡ Some False

let example1 = assert : map Natural Bool Natural/even (None Natural) ≡ None Bool

in map