Merge pull request #1137 from zainab-ali/vector1

Adding NonEmptyVector

core/src/main/scala/cats/data/NonEmptyVector.scala

@@ -0,0 +1,226 @@
+package cats
+package data
+
+import scala.annotation.tailrec
+import scala.collection.immutable.VectorBuilder
+import cats.instances.vector._
+
+/**
+ * A data type which represents a non empty Vector.
+ */
+final case class NonEmptyVector[A] private (toVector: Vector[A]) {
+
+  /** Gets the element at the index, if it exists */
+  def get(i: Int): Option[A] =
+    toVector.lift(i)
+
+  /** Gets the element at the index, or throws an exception if none exists */
+  def getUnsafe(i: Int): A = toVector(i)
+
+  /** Updates the element at the index, if it exists */
+  def updated(i: Int, a: A): Option[NonEmptyVector[A]] =
+    if (toVector.isDefinedAt(i)) Some(NonEmptyVector(toVector.updated(i, a))) else None
+
+  /** Updates the element at the index, or throws an exeption if none exists */
+  def updatedUnsafe(i: Int, a: A):
+      NonEmptyVector[A] = NonEmptyVector(toVector.updated(i, a))
+
+  def head: A = toVector.head
+
+  def tail: Vector[A] = toVector.tail
+
+  /**
+   * remove elements not matching the predicate
+   */
+  def filter(f: A => Boolean): Vector[A] = toVector.filter(f)
+
+  /**
+   * Append another NonEmptyVector to this
+   */
+  def concat(other: NonEmptyVector[A]): NonEmptyVector[A] = NonEmptyVector(toVector ++ other.toVector)
+
+  /**
+    * Alias for concat
+    */
+  def ++(other: NonEmptyVector[A]): NonEmptyVector[A] = concat(other)
+
+  /**
+   * Append another Vector to this
+   */
+  def concat(other: Vector[A]): NonEmptyVector[A] = NonEmptyVector(toVector ++ other)
+
+  /**
+    * Alias for concat
+    */
+  def ++(other: Vector[A]): NonEmptyVector[A] = concat(other)
+
+  /**
+   * find the first element matching the predicate, if one exists
+   */
+  def find(f: A => Boolean): Option[A] = toVector.find(f)
+
+  /**
+   * Check whether at least one element satisfies the predicate.
+   */
+  def exists(f: A => Boolean): Boolean = toVector.exists(f)
+
+  /**
+   * Check whether all elements satisfy the predicate.
+   */
+  def forall(f: A => Boolean): Boolean = toVector.forall(f)
+
+  /**
+   * Left-associative fold using f.
+   */
+  def foldLeft[B](b: B)(f: (B, A) => B): B =
+    toVector.foldLeft(b)(f)
+
+  /**
+   * Right-associative fold using f.
+   */
+  def foldRight[B](lb: Eval[B])(f: (A, Eval[B]) => Eval[B]): Eval[B] =
+    Foldable[Vector].foldRight(toVector, lb)(f)
+
+  /**
+    * Applies f to all the elements
+    */
+  def map[B](f: A => B): NonEmptyVector[B] =
+    NonEmptyVector(toVector.map(f))
+
+  /**
+    *  Applies f to all elements and combines the result
+    */
+  def flatMap[B](f: A => NonEmptyVector[B]): NonEmptyVector[B] =
+    NonEmptyVector(toVector.flatMap(a => f(a).toVector))
+
+  /**
+    * Left-associative reduce using f.
+    */
+  def reduceLeft(f: (A, A) => A): A =
+    tail.foldLeft(head)(f)
+
+  /**
+    * Reduce using the Semigroup of A
+    */
+  def reduce(implicit S: Semigroup[A]): A =
+    S.combineAllOption(toVector).get
+
+  /**
+   * Typesafe equality operator.
+   *
+   * This method is similar to == except that it only allows two
+   * NonEmptyVector[A] values to be compared to each other, and uses
+   * equality provided by Eq[_] instances, rather than using the
+   * universal equality provided by .equals.
+   */
+  def ===(that: NonEmptyVector[A])(implicit A: Eq[A]): Boolean = Eq[Vector[A]].eqv(toVector, that.toVector)
+
+  /**
+   * Typesafe stringification method.
+   *
+   * This method is similar to .toString except that it stringifies
+   * values according to Show[_] instances, rather than using the
+   * universal .toString method.
+   */
+  def show(implicit A: Show[A]): String =
+    s"NonEmptyVector(${Show[Vector[A]].show(toVector)})"
+}
+
+private[data] sealed trait NonEmptyVectorInstances {
+
+  implicit val catsDataInstancesForNonEmptyVector: SemigroupK[NonEmptyVector] with Reducible[NonEmptyVector]
+      with Comonad[NonEmptyVector] with Traverse[NonEmptyVector] with MonadRec[NonEmptyVector] =
+    new NonEmptyReducible[NonEmptyVector, Vector] with SemigroupK[NonEmptyVector]
+        with Comonad[NonEmptyVector] with Traverse[NonEmptyVector] with MonadRec[NonEmptyVector] {
+
+      def combineK[A](a: NonEmptyVector[A], b: NonEmptyVector[A]): NonEmptyVector[A] =
+        a concat b
+
+      override def split[A](fa: NonEmptyVector[A]): (A, Vector[A]) = (fa.head, fa.tail)
+
+      override def size[A](fa: NonEmptyVector[A]): Long = 1 + fa.tail.size.toLong
+
+      override def reduceLeft[A](fa: NonEmptyVector[A])(f: (A, A) => A): A =
+        fa.reduceLeft(f)
+
+      override def reduce[A](fa: NonEmptyVector[A])(implicit A: Semigroup[A]): A =
+        fa.reduce
+
+      override def map[A, B](fa: NonEmptyVector[A])(f: A => B): NonEmptyVector[B] =
+        fa map f
+
+      def pure[A](x: A): NonEmptyVector[A] =
+        NonEmptyVector(x, Vector.empty)
+
+      def flatMap[A, B](fa: NonEmptyVector[A])(f: A => NonEmptyVector[B]): NonEmptyVector[B] =
+        fa flatMap f
+
+      def coflatMap[A, B](fa: NonEmptyVector[A])(f: NonEmptyVector[A] => B): NonEmptyVector[B] = {
+        @tailrec def consume(as: Vector[A], buf: VectorBuilder[B]): Vector[B] =
+          as match {
+            case a +: as => consume(as, buf += f(NonEmptyVector(a, as)))
+            case _ => buf.result()
+          }
+        NonEmptyVector(f(fa), consume(fa.tail, new VectorBuilder[B]))
+      }
+
+      def extract[A](fa: NonEmptyVector[A]): A = fa.head
+
+      def traverse[G[_], A, B](fa: NonEmptyVector[A])(f: (A) => G[B])(implicit G: Applicative[G]): G[NonEmptyVector[B]] =
+      G.map2Eval(f(fa.head), Always(Traverse[Vector].traverse(fa.tail)(f)))(NonEmptyVector(_, _)).value
+
+
+      override def foldLeft[A, B](fa: NonEmptyVector[A], b: B)(f: (B, A) => B): B =
+        fa.foldLeft(b)(f)
+
+      override def foldRight[A, B](fa: NonEmptyVector[A], lb: Eval[B])(f: (A, Eval[B]) => Eval[B]): Eval[B] =
+        fa.foldRight(lb)(f)
+
+      def tailRecM[A, B](a: A)(f: A => NonEmptyVector[A Xor B]): NonEmptyVector[B] = {
+        val buf = new VectorBuilder[B]
+        @tailrec def go(v: NonEmptyVector[A Xor B]): Unit = v.head match {
+            case Xor.Right(b) =>
+            buf += b
+            NonEmptyVector.fromVector(v.tail) match {
+              case Some(t) => go(t)
+              case None => ()
+            }
+          case Xor.Left(a) => go(f(a).concat(v.tail))
+          }
+        go(f(a))
+        NonEmptyVector.fromVectorUnsafe(buf.result())
+      }
+    }
+
+  implicit def catsDataEqForNonEmptyVector[A](implicit A: Eq[A]): Eq[NonEmptyVector[A]] =
+    new Eq[NonEmptyVector[A]]{
+      def eqv(x: NonEmptyVector[A], y: NonEmptyVector[A]): Boolean = x === y
+    }
+
+  implicit def catsDataShowForNonEmptyVector[A](implicit A: Show[A]): Show[NonEmptyVector[A]] =
+    Show.show[NonEmptyVector[A]](_.show)
+
+  implicit def catsDataSemigroupForNonEmptyVector[A]: Semigroup[NonEmptyVector[A]] =
+    catsDataInstancesForNonEmptyVector.algebra
+
+}
+
+object NonEmptyVector extends NonEmptyVectorInstances {
+
+  def apply[A](head: A, tail: Vector[A]): NonEmptyVector[A] =
+    NonEmptyVector(head +: tail)
+
+  def apply[A](head: A, tail: A*): NonEmptyVector[A] = {
+    val buf = Vector.newBuilder[A]
+    buf += head
+    tail.foreach(buf += _)
+    NonEmptyVector(buf.result)
+  }
+
+  def fromVector[A](vector: Vector[A]): Option[NonEmptyVector[A]] =
+    if (vector.isEmpty) None else Some(new NonEmptyVector(vector))
+
+  def fromVectorUnsafe[A](vector: Vector[A]): NonEmptyVector[A] =
+    if (vector.nonEmpty) NonEmptyVector(vector)
+    else throw new IllegalArgumentException("Cannot create NonEmptyVector from empty vector")
+}

core/src/main/scala/cats/data/package.scala

@@ -2,7 +2,6 @@ package cats
 
 package object data {
   type NonEmptyList[A] = OneAnd[List, A]
-  type NonEmptyVector[A] = OneAnd[Vector, A]
   type NonEmptyStream[A] = OneAnd[Stream, A]
   type ValidatedNel[E, A] = Validated[NonEmptyList[E], A]
 
@@ -11,11 +10,6 @@ package object data {
   def NonEmptyList[A](head: A, tail: A*): NonEmptyList[A] =
     OneAnd[List, A](head, tail.toList)
 
-  def NonEmptyVector[A](head: A, tail: Vector[A] = Vector.empty): NonEmptyVector[A] =
-    OneAnd(head, tail)
-  def NonEmptyVector[A](head: A, tail: A*): NonEmptyVector[A] =
-    OneAnd(head, tail.toVector)
-
   def NonEmptyStream[A](head: A, tail: Stream[A] = Stream.empty): NonEmptyStream[A] =
     OneAnd(head, tail)
   def NonEmptyStream[A](head: A, tail: A*): NonEmptyStream[A] =

docs/src/main/tut/oneand.md

@@ -21,10 +21,10 @@ type NonEmptyList[A] = OneAnd[List, A]
 
 which is the actual implementation of non-empty lists in cats.  By
 having the higher kinded type parameter `F[_]`, `OneAnd` is also able
-to represent other "non-empty" data structures, e.g.
+to represent other "non-empty" data structures e.g.
 
 ```tut:silent
 import cats.data.OneAnd
 
-type NonEmptyVector[A] = OneAnd[Vector, A]
-```
+type NonEmptyStream[A] = OneAnd[Stream, A]
+```

laws/src/main/scala/cats/laws/discipline/Arbitrary.scala

@@ -23,6 +23,9 @@ object arbitrary extends ArbitraryInstances0 {
   implicit def catsLawsArbitraryForOneAnd[F[_], A](implicit A: Arbitrary[A], F: Arbitrary[F[A]]): Arbitrary[OneAnd[F, A]] =
     Arbitrary(F.arbitrary.flatMap(fa => A.arbitrary.map(a => OneAnd(a, fa))))
 
+  implicit def catsLawsArbitraryForNonEmptyVector[A](implicit A: Arbitrary[A]): Arbitrary[NonEmptyVector[A]] =
+    Arbitrary(implicitly[Arbitrary[Vector[A]]].arbitrary.flatMap(fa => A.arbitrary.map(a => NonEmptyVector(a, fa))))
+
   implicit def catsLawsArbitraryForXor[A, B](implicit A: Arbitrary[A], B: Arbitrary[B]): Arbitrary[A Xor B] =
     Arbitrary(Gen.oneOf(A.arbitrary.map(Xor.left), B.arbitrary.map(Xor.right)))