--- ./MyPlayground.playground/Contents.swift.org	2018-08-26 17:50:44.000000000 +0900
+++ ./MyPlayground.playground/Contents.swift	2021-09-22 13:06:59.937955100 +0900
@@ -1,6 +1,8 @@
 //: Playground - noun: a place where people can play
 
+#if canImport(UIKit)
 import UIKit
+#endif
 
 var str = "Hello, playground"
 
--- ./MyPlayground11.playground/Contents.swift.org	2018-08-28 17:41:20.000000000 +0900
+++ ./MyPlayground11.playground/Contents.swift	2021-09-22 13:24:51.064907200 +0900
@@ -1,6 +1,8 @@
 //: Playground - noun: a place where people can play
 
+#if !os(Linux)
 import Cocoa
+#endif
 
 var str = "Hello, playground"
 
--- ./MyPlayground5.playground/Contents.swift.org	2018-08-28 17:24:22.000000000 +0900
+++ ./MyPlayground5.playground/Contents.swift	2021-09-22 13:21:58.487186900 +0900
@@ -1,6 +1,8 @@
 //: Playground - noun: a place where people can play
 
+#if !os(Linux)
 import Cocoa
+#endif
 
 var str = "Hello, playground"
 
--- ./MyPlayground8.playground/Contents.swift.org	2018-08-28 17:37:30.000000000 +0900
+++ ./MyPlayground8.playground/Contents.swift	2021-09-22 13:16:27.876465300 +0900
@@ -1,6 +1,8 @@
 //: Playground - noun: a place where people can play
 
+#if !os(Linux)
 import Cocoa
+#endif
 
 var str = "Hello, playground"
 
@@ -170,6 +172,7 @@
 let efficiency: FuelEfficiency = car2
 efficiency.fuelEfficiency // 200 / 10
 
+#if !os(Linux)
 /*
  プロトコル拡張(荻原P.251,荻原第３版P.250)
  
@@ -328,3 +331,4 @@
     julianOneDay.lastDayOfMonth     // 29
     julianOneDay.modifiedJulianDay  // 58899
 }
+#endif