diff --git a/core/src/main/scala-2.13+/cats/data/NonEmptyLazyList.scala b/core/src/main/scala-2.13+/cats/data/NonEmptyLazyList.scala index 746d115f686..c12e3895397 100644 --- a/core/src/main/scala-2.13+/cats/data/NonEmptyLazyList.scala +++ b/core/src/main/scala-2.13+/cats/data/NonEmptyLazyList.scala @@ -62,15 +62,47 @@ object NonEmptyLazyList extends NonEmptyLazyListInstances { def fromSeq[A](as: Seq[A]): Option[NonEmptyLazyList[A]] = if (as.nonEmpty) Option(create(LazyList.from(as))) else None - def fromLazyListPrepend[A](a: A, ca: LazyList[A]): NonEmptyLazyList[A] = - create(a +: ca) + def fromLazyListPrepend[A](a: => A, ll: => LazyList[A]): NonEmptyLazyList[A] = + create(a #:: ll) - def fromLazyListAppend[A](ca: LazyList[A], a: A): NonEmptyLazyList[A] = - create(ca :+ a) + def fromLazyListAppend[A](ll: => LazyList[A], a: => A): NonEmptyLazyList[A] = + create(ll #::: a #:: LazyList.empty) def apply[A](a: => A, as: A*): NonEmptyLazyList[A] = create(a #:: LazyList.from(as)) + // allows the creation of fully lazy `NonEmptyLazyList`s by prepending to this + def maybe[A](ll: => LazyList[A]): Maybe[A] = new Maybe(() => ll) + + final class Maybe[A] private[NonEmptyLazyList] (private[this] var mkLL: () => LazyList[A]) { + // because instances of this class are created explicitly, they might be + // reused, and we don't want to re-evaluate `mkLL` + private[this] lazy val ll = { + val res = mkLL() + mkLL = null // allow GC + res + } + + def #::[B >: A](elem: => B): NonEmptyLazyList[B] = + create(elem #:: ll) + def #:::[B >: A](prefix: => NonEmptyLazyList[B]): NonEmptyLazyList[B] = + create(prefix.toLazyList #::: ll) + def #:::[B >: A](prefix: => LazyList[B]): Maybe[B] = + new Maybe(() => prefix #::: ll) + } + + final class Deferrer[A] private[NonEmptyLazyList] (private val nell: () => NonEmptyLazyList[A]) extends AnyVal { + def #::[B >: A](elem: => B): NonEmptyLazyList[B] = + create(elem #:: nell().toLazyList) + def #:::[B >: A](prefix: => NonEmptyLazyList[B]): NonEmptyLazyList[B] = + create(prefix.toLazyList #::: nell().toLazyList) + def #:::[B >: A](prefix: => LazyList[B]): NonEmptyLazyList[B] = + create(prefix #::: nell().toLazyList) + } + + implicit def toDeferrer[A](nell: => NonEmptyLazyList[A]): Deferrer[A] = + new Deferrer(() => nell) + implicit def catsNonEmptyLazyListOps[A](value: NonEmptyLazyList[A]): NonEmptyLazyListOps[A] = new NonEmptyLazyListOps(value) } @@ -118,11 +150,7 @@ class NonEmptyLazyListOps[A](private val value: NonEmptyLazyList[A]) final def +:[AA >: A](a: AA): NonEmptyLazyList[AA] = prepend(a) - /** - * Alias for [[prepend]]. - */ - // TODO: `a` should be by-name and this method should not be listed as an - // alias for `prepend`, but it's too late to change that in this version + @deprecated("use Deferrer construction instead") final def #::[AA >: A](a: AA): NonEmptyLazyList[AA] = prepend(a) @@ -139,52 +167,76 @@ class NonEmptyLazyListOps[A](private val value: NonEmptyLazyList[A]) append(a) /** - * concatenates this with `ll` + * Concatenates this with `ll`; equivalent to `appendLazyList` + */ + final def concat[AA >: A](ll: => LazyList[AA]): NonEmptyLazyList[AA] = + appendLazyList(ll) + + /** + * Alias for `concat` */ - final def concat[AA >: A](ll: LazyList[AA]): NonEmptyLazyList[AA] = - create(toLazyList ++ ll) + final def ++[AA >: A](ll: => LazyList[AA]): NonEmptyLazyList[AA] = + concat(ll) /** - * Concatenates this with `nell` + * Concatenates this with `nell`; equivalent to `appendNell` */ - final def concatNell[AA >: A](nell: NonEmptyLazyList[AA]): NonEmptyLazyList[AA] = - create(toLazyList ++ nell.toLazyList) + final def concatNell[AA >: A](nell: => NonEmptyLazyList[AA]): NonEmptyLazyList[AA] = + appendNell(nell) /** - * Alias for concatNell + * Alias for `concatNell` */ - final def ++[AA >: A](nell: NonEmptyLazyList[AA]): NonEmptyLazyList[AA] = + final def ++[AA >: A](nell: => NonEmptyLazyList[AA]): NonEmptyLazyList[AA] = concatNell(nell) /** * Appends the given LazyList */ - final def appendLazyList[AA >: A](nell: LazyList[AA]): NonEmptyLazyList[AA] = - create(toLazyList ++ nell) + final def appendLazyList[AA >: A](ll: => LazyList[AA]): NonEmptyLazyList[AA] = + create(toLazyList #::: ll) /** * Alias for `appendLazyList` */ - final def :++[AA >: A](c: LazyList[AA]): NonEmptyLazyList[AA] = - appendLazyList(c) + final def :++[AA >: A](ll: => LazyList[AA]): NonEmptyLazyList[AA] = + appendLazyList(ll) + + /** + * Prepends the given NonEmptyLazyList + */ + final def appendNell[AA >: A](nell: => NonEmptyLazyList[AA]): NonEmptyLazyList[AA] = + create(toLazyList #::: nell.toLazyList) + + /** + * Alias for `appendNell` + */ + final def :++[AA >: A](nell: => NonEmptyLazyList[AA]): NonEmptyLazyList[AA] = + appendNell(nell) /** * Prepends the given LazyList */ - final def prependLazyList[AA >: A](c: LazyList[AA]): NonEmptyLazyList[AA] = - create(c ++ toLazyList) + final def prependLazyList[AA >: A](ll: => LazyList[AA]): NonEmptyLazyList[AA] = + create(ll #::: toLazyList) + + /** + * Alias for `prependLazyList` + */ + final def ++:[AA >: A](ll: => LazyList[AA]): NonEmptyLazyList[AA] = + prependLazyList(ll) /** * Prepends the given NonEmptyLazyList */ - final def prependNell[AA >: A](c: NonEmptyLazyList[AA]): NonEmptyLazyList[AA] = - create(c.toLazyList ++ toLazyList) + final def prependNell[AA >: A](nell: => NonEmptyLazyList[AA]): NonEmptyLazyList[AA] = + create(nell.toLazyList #::: toLazyList) /** * Alias for `prependNell` */ - final def ++:[AA >: A](c: NonEmptyLazyList[AA]): NonEmptyLazyList[AA] = - prependNell(c) + final def ++:[AA >: A](nell: => NonEmptyLazyList[AA]): NonEmptyLazyList[AA] = + prependNell(nell) /** * Converts this NonEmptyLazyList to a `NonEmptyList`.