Add Swift Playground for chmod calculator

ChmodHelper.playground/Contents.swift

@@ -0,0 +1,65 @@
+import SwiftUI
+import PlaygroundSupport
+
+struct PermissionGroup {
+    var read: Bool = false
+    var write: Bool = false
+    var execute: Bool = false
+
+    var value: Int {
+        (read ? 4 : 0) + (write ? 2 : 0) + (execute ? 1 : 0)
+    }
+}
+
+extension Binding where Value == PermissionGroup {
+    var read: Binding<Bool> {
+        Binding<Bool>(
+            get: { self.wrappedValue.read },
+            set: { self.wrappedValue.read = $0 }
+        )
+    }
+    var write: Binding<Bool> {
+        Binding<Bool>(
+            get: { self.wrappedValue.write },
+            set: { self.wrappedValue.write = $0 }
+        )
+    }
+    var execute: Binding<Bool> {
+        Binding<Bool>(
+            get: { self.wrappedValue.execute },
+            set: { self.wrappedValue.execute = $0 }
+        )
+    }
+}
+
+struct ContentView: View {
+    @State private var owner = PermissionGroup()
+    @State private var group = PermissionGroup()
+    @State private var others = PermissionGroup()
+
+    var body: some View {
+        NavigationView {
+            Form {
+                Section(header: Text("Owner")) { toggles(for: $owner) }
+                Section(header: Text("Group")) { toggles(for: $group) }
+                Section(header: Text("Others")) { toggles(for: $others) }
+                Section(header: Text("Octal")) {
+                    Text("\(owner.value)\(group.value)\(others.value)")
+                        .font(.largeTitle)
+                        .frame(maxWidth: .infinity, alignment: .center)
+                }
+            }
+            .navigationBarTitle("Chmod Helper")
+        }
+    }
+
+    func toggles(for group: Binding<PermissionGroup>) -> some View {
+        VStack(alignment: .leading) {
+            Toggle("Read", isOn: group.read)
+            Toggle("Write", isOn: group.write)
+            Toggle("Execute", isOn: group.execute)
+        }
+    }
+}
+
+PlaygroundPage.current.setLiveView(ContentView())

ChmodHelper.playground/contents.xcplayground

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

ChmodHelper.playground/timeline.xctimeline

@@ -0,0 +1,3 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Timeline version="1.0">
+</Timeline>

README.md

@@ -103,3 +103,7 @@ I'd love to see the sites you create using this little tool.
 
 ## License
 [MIT License](LICENSE)
+
+## Swift Playground
+A Swift playground implementation of the permission calculator is provided in `ChmodHelper.playground`. Open this folder with the Swift Playgrounds app on iPad to interactively select permission bits and see the resulting octal value.
+