Merge pull request #592 from remlostime/lru-swift

[Swift 4] Update LRU Cache

Author: kelvinlauKL

LRU Cache/LRUCache.playground/Contents.swift

@@ -1,3 +1,8 @@
+// last checked with Xcode 9.0b4
+#if swift(>=4.0)
+print("Hello, Swift 4!")
+#endif
+
 let cache = LRUCache<String>(2)
 cache.set("a", val: 1)
 cache.set("b", val: 2)