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# NonEmpty (aka NEList) — foundational non-empty list for Bend.# Publish entry for this package. Depends only on Base (does not reimplement List).## Encoding: head + List tail. Emptiness is unrepresentable by construction.# Quantity: NonEmpty<a, A> is Kind(a), same convention as List/Maybe.import Basetype NonEmpty<a, -A: Kind(a)> is Kind(a):  NE{head: A, tail: List<a, A>}def NonEmpty.one(a, -A: Kind(a), x: A) -> NonEmpty<a, A>:  NE{x, Nil{}}def NonEmpty.cons(a, -A: Kind(a), x: A, xs: NonEmpty<a, A>) -> NonEmpty<a, A>:  match xs:    case NE{h, t}:      NE{x, h <> t}def NonEmpty.from_list(a, -A: Kind(a), xs: List<a, A>) -> Maybe<a, NonEmpty<a, A>>:  match xs:    case Nil{}:      None{}    case h <> t:      Some{NE{h, t}}def NonEmpty.to_list(a, -A: Kind(a), xs: NonEmpty<a, A>) -> List<a, A>:  match xs:    case NE{h, t}:      h <> tdef NonEmpty.head(a, -A: Kind(a), xs: NonEmpty<a, A>) -> A:  match xs:    case NE{h, t}:      hdef NonEmpty.tail(a, -A: Kind(a), xs: NonEmpty<a, A>) -> List<a, A>:  match xs:    case NE{h, t}:      tdef NonEmpty.length(a, -A: Kind(a), xs: NonEmpty<a, A>) -> Nat:  match xs:    case NE{h, t}:      1n+List.length(a, A, t)# Template map, same shape as List.map (affine NonEmpty<A> = NonEmpty<&1, A>).def NonEmpty.map(~A: Type, ~B: Type, ~f: A -> B, xs: NonEmpty<A>) -> NonEmpty<B>:  match xs:    case NE{h, t}:      NE{f(h), List.map(~A, ~B, ~f, t)}def NonEmpty.append(a, -A: Kind(a), xs: NonEmpty<a, A>, ys: NonEmpty<a, A>) ->  NonEmpty<a, A>:  match xs:    case NE{h, t}:      match ys:        case NE{yh, yt}:          NE{h, List.append(a, A, t, yh <> yt)}def NonEmpty.snoc(a, -A: Kind(a), xs: NonEmpty<a, A>, y: A) -> NonEmpty<a, A>:  match xs:    case NE{h, t}:      NE{h, List.append(a, A, t, y <> Nil{})}