/Prelude-v23.0.0/NonEmpty/indexed.dhall

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Tag each element of the NonEmpty list with its index

Examples

  indexed Bool { head = True, tail = [ False, True ] }
≡ { head = { index = 0, value = True }
, tail = [ { index = 1, value = False }, { index = 2, value = True } ]
}
  indexed Bool { head = True, tail = [] : List Bool }
≡ { head = { index = 0, value = True }
, tail = [] : List { index : Natural, value : Bool }
}

Source

--| Tag each element of the `NonEmpty` list with its index
let NonEmpty =
missing sha256:e2e247455a858317e470e0e4affca8ac07f9f130570ece9cb7ac1f4ea3deb87f
? ./Type.dhall

let List/map =
missing sha256:dd845ffb4568d40327f2a817eb42d1c6138b929ca758d50bc33112ef3c885680
? ../List/map.dhall

let indexed
: ∀(a : Type) → NonEmpty a → NonEmpty { index : Natural, value : a }
= λ(a : Type) →
λ(xs : NonEmpty a) →
{ head = { index = 0, value = xs.head }
, tail =
List/map
{ index : Natural, value : a }
{ index : Natural, value : a }
( λ(ix : { index : Natural, value : a }) →
{ index = ix.index + 1, value = ix.value }
)
(List/indexed a xs.tail)
}

let example0 =
assert
: indexed Bool { head = True, tail = [ False, True ] }
≡ { head = { index = 0, value = True }
, tail = [ { index = 1, value = False }, { index = 2, value = True } ]
}

let example1 =
assert
: indexed Bool { head = True, tail = [] : List Bool }
≡ { head = { index = 0, value = True }
, tail = [] : List { index : Natural, value : Bool }
}

in indexed