From 568e48961e423a1dd1425c2c65bc129edba3f700 Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Wed, 27 Jul 2016 10:06:35 +0200
Subject: Improve drop

By making LinearSeq an IterableLike, we can use tail-recursion
on drop.
---
 tests/run/colltest6/CollectionStrawMan6_1.scala | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

(limited to 'tests')

diff --git a/tests/run/colltest6/CollectionStrawMan6_1.scala b/tests/run/colltest6/CollectionStrawMan6_1.scala
index b5776433e..1cd841336 100644
--- a/tests/run/colltest6/CollectionStrawMan6_1.scala
+++ b/tests/run/colltest6/CollectionStrawMan6_1.scala
@@ -138,7 +138,7 @@ object CollectionStrawMan6 extends LowPriority {
   }
 
   /** Base trait for linearly accessed sequences */
-  trait LinearSeq[+A] extends Seq[A] { self =>
+  trait LinearSeq[+A] extends Seq[A] with SeqLike[A, LinearSeq] { self =>
 
     def iterator = new Iterator[A] {
       private[this] var current: Seq[A] = self
@@ -154,15 +154,8 @@ object CollectionStrawMan6 extends LowPriority {
     def length: Int = if (isEmpty) 0 else 1 + tail.length
 
     /** Optimized version of `drop` that avoids copying */
-    final override def drop(n: Int) = {
-      var current: Seq[A] = this
-      var i = n
-      while (i > 0) {
-        current = current.tail
-        i -= 1
-      }
-      current
-    }
+    @tailrec final override def drop(n: Int) =
+      if (n <= 0) this else tail.drop(n - 1)
   }
 
   /** Base trait for strict collections that can be built using a builder.
-- 
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