fix in Range

core/src/main/scala/cats/collections/Range.scala

@@ -21,12 +21,14 @@
 
 package cats.collections
 
-import cats.{Eq, Order, Show}
+import cats.Eq
+import cats.Order
+import cats.Show
 
 /**
  * Represent an inclusive range [x, y] that can be generated by using discrete operations
  */
-final case class Range[A](val start: A, val end: A) {
+final case class Range[A](start: A, end: A) {
 
   /**
    * Subtract a Range from this range. The result will be 0, 1 or 2 ranges
@@ -77,13 +79,12 @@ final case class Range[A](val start: A, val end: A) {
    * the start's successor.
    */
   def toIterator(implicit discrete: Discrete[A], order: Order[A]): Iterator[A] = {
-    val next: A => A = a => if (order.lteqv(a, end)) discrete.succ(a) else discrete.pred(a)
+    val next: A => A = if (order.lt(start, end)) discrete.succ(_) else discrete.pred(_)
 
-    Stream
+    Iterator
       .iterate(start)(next)
-      .takeWhile(concurrent => !order.eqv(concurrent, end))
-      .append(Seq(end))
-      .iterator
+      .takeWhile(order.neqv(_, end))
+      .++(Iterator.single(end))
   }
 
   /**
@@ -103,14 +104,18 @@ final case class Range[A](val start: A, val end: A) {
   def contains(x: A)(implicit A: Order[A]): Boolean = A.gteqv(x, start) && A.lteqv(x, end)
 
   /**
-   * Apply function f to each element in range [star, end]
+   * Apply function f to each element in range `[star, end]`. Does nothing if `end` precedes `start`.
    */
   def foreach(f: A => Unit)(implicit discrete: Discrete[A], order: Order[A]): Unit = {
     var i = start
-    while (order.lteqv(i, end)) {
+    // Visit values in range [start, end), i.e. excluding `end`.
+    while (order.lt(i, end)) {
       f(i)
       i = discrete.succ(i)
     }
+    // Visit the last (or the only) value, if any.
+    if (order.eqv(i, end))
+      f(i)
   }
 
   def map[B](f: A => B): Range[B] = Range[B](f(start), f(end))