/Prelude-v22.0.0/Optional/concatMap.dhall
Copy path to clipboardTransform the value with a function and flatten the resulting Optional
Examples
concatMap Natural Natural exampleFun (Some 1) ≡ None Natural
concatMap Natural Natural exampleFun (Some 2) ≡ Some 3
concatMap Natural Natural exampleFun (None Natural) ≡ None Natural
Source
--| Transform the value with a function and flatten the resulting `Optional`
let concatMap
: ∀(a : Type) → ∀(b : Type) → (a → Optional b) → Optional a → Optional b
= λ(a : Type) →
λ(b : Type) →
λ(f : a → Optional b) →
λ(o : Optional a) →
merge { Some = f, None = None b } o
let exampleFun
: Natural → Optional Natural
= λ(n : Natural) → if Natural/even n then Some (n + 1) else None Natural
let example0 =
assert : concatMap Natural Natural exampleFun (Some 1) ≡ None Natural
let example1 = assert : concatMap Natural Natural exampleFun (Some 2) ≡ Some 3
let example2 =
assert
: concatMap Natural Natural exampleFun (None Natural) ≡ None Natural
in concatMap