added Chain#takeWhile and Chain#dropWhile

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

@@ -160,6 +160,40 @@ sealed abstract class Chain[+A] {
     result
   }
 
+  /**
+   * Takes longest prefix of elements that satisfy a predicate.
+   * @param p The predicate used to test elements.
+   * @return the longest prefix of this chain whose elements all satisfy the predicate p.
+   */
+  final def takeWhile(p: A => Boolean): Chain[A] = {
+    var result = Chain.empty[A]
+    foreachUntil { a =>
+      val pr = p(a)
+      if (pr) result = result :+ a
+      !pr
+    }
+    result
+  }
+
+  /**
+   * Drops longest prefix of elements that satisfy a predicate.
+   *
+   * @param p The predicate used to test elements.
+   * @return the longest suffix of this sequence whose first element does not satisfy the predicate p.
+   */
+  final def dropWhile(p: A => Boolean): Chain[A] = {
+    @tailrec
+    def go(rem: Chain[A]): Chain[A] =
+      rem.uncons match {
+        case Some((a, tail)) =>
+          if (p(a)) go(tail)
+          else rem
+
+        case None => nil
+      }
+    go(this)
+  }
+
   /**
    * Folds over the elements from right to left using the supplied initial value and function.
    */

tests/src/test/scala/cats/tests/ChainSuite.scala

@@ -224,4 +224,17 @@ class ChainSuite extends CatsSuite {
       x.hashCode should ===(x.toList.hashCode)
     }
   }
+
+  test("Chain#takeWhile is consistent with List#takeWhile") {
+    forAll { (x: Chain[Int], p: Int => Boolean) =>
+      x.takeWhile(p).toList should ===(x.toList.takeWhile(p))
+    }
+  }
+
+  test("Chain#dropWhile is consistent with List#dropWhile") {
+    forAll { (x: Chain[Int], p: Int => Boolean) =>
+      x.dropWhile(p).toList should ===(x.toList.dropWhile(p))
+    }
+  }
+
 }