[Swift 4 Update]add parentheses

Single argument function types require parentheses

Author: iWeslie

Binary Tree/BinaryTree.swift

@@ -29,23 +29,23 @@ extension BinaryTree: CustomStringConvertible {
 }
 
 extension BinaryTree {
-  public func traverseInOrder(process: T -> Void) {
+  public func traverseInOrder(process: (T) -> Void) {
     if case let .node(left, value, right) = self {
       left.traverseInOrder(process: process)
       process(value)
       right.traverseInOrder(process: process)
     }
   }
 
-  public func traversePreOrder(process: T -> Void) {
+  public func traversePreOrder(process: (T) -> Void) {
     if case let .node(left, value, right) = self {
       process(value)
       left.traversePreOrder(process: process)
       right.traversePreOrder(process: process)
     }
   }
 
-  public func traversePostOrder(process: T -> Void) {
+  public func traversePostOrder(process: (T) -> Void) {
     if case let .node(left, value, right) = self {
       left.traversePostOrder(process: process)
       right.traversePostOrder(process: process)