/Prelude-v21.1.0/NonEmpty/reverse.dhall

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Reverse a NonEmpty list

Examples

reverse Natural { head = 0, tail = [ 1, 2 ] } ≡ { head = 2, tail = [ 1, 0 ] }
  reverse Natural { head = 0, tail = [] : List Natural }
≡ { head = 0, tail = [] : List Natural }

Source

--| Reverse a `NonEmpty` list
let NonEmpty =
./Type.dhall sha256:e2e247455a858317e470e0e4affca8ac07f9f130570ece9cb7ac1f4ea3deb87f
? ./Type.dhall

let List/drop =
../List/drop.dhall sha256:af983ba3ead494dd72beed05c0f3a17c36a4244adedf7ced502c6512196ed0cf
? ../List/drop.dhall

let reverse
: ∀(a : Type) → NonEmpty a → NonEmpty a
= λ(a : Type) →
λ(xs : NonEmpty a) →
let ys = List/reverse a xs.tail

in merge
{ Some =
λ(y : a) → { head = y, tail = List/drop 1 a ys # [ xs.head ] }
, None = { head = xs.head, tail = [] : List a }
}
(List/head a ys)

let example =
assert
: reverse Natural { head = 0, tail = [ 1, 2 ] }
≡ { head = 2, tail = [ 1, 0 ] }

let example1 =
assert
: reverse Natural { head = 0, tail = [] : List Natural }
≡ { head = 0, tail = [] : List Natural }

in reverse