/Prelude-v22.0.0/List/drop.dhall

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Remove first n elements of a list

Examples

drop 2 Natural [ 2, 3, 5 ] ≡ [ 5 ]
drop 5 Natural [ 2, 3, 5 ] ≡ ([] : List Natural)

Source

--| Remove first `n` elements of a list
let Natural/greaterThanEqual =
../Natural/greaterThanEqual.dhall sha256:30ebfab0febd7aa0ccccfdf3dc36ee6d50f0117f35dd4a9b034750b7e885a1a4
? ../Natural/greaterThanEqual.dhall

let drop
: ∀(n : Natural) → ∀(a : Type) → List a → List a
= λ(n : Natural) →
λ(a : Type) →
λ(xs : List a) →
List/fold
{ index : Natural, value : a }
(List/indexed a xs)
(List a)
( λ(x : { index : Natural, value : a }) →
λ(xs : List a) →
if Natural/greaterThanEqual x.index n
then [ x.value ] # xs
else xs
)
([] : List a)

let example = assert : drop 2 Natural [ 2, 3, 5 ] ≡ [ 5 ]

let example = assert : drop 5 Natural [ 2, 3, 5 ] ≡ ([] : List Natural)

in drop