alskipp · November 1, 2018 11:10 · Feb 27, 2015 · Feb 27, 2015 · Feb 27, 2015 · Oct 28, 2014
diff --git a/encrypt_xor1.swift b/encrypt_xor1.swift
@@ -9,7 +9,7 @@ extension Character {
 
 func encrypt(c:Character, key:Character) -> String {
     let byte = [c.utf8() ^ key.utf8()]
-    return String(bytes: byte, encoding: NSUTF8StringEncoding)!
+    return String(bytes: byte, encoding: NSUTF8StringEncoding)! // forced unwrapping alert!
 }
 
 func encrypt(message:String, #key:String) -> String {

diff --git a/encrypt_xor2.swift b/encrypt_xor2.swift
@@ -1,4 +1,4 @@
-/*
+/* (Requires Swift 1.2)
 In the version above you'll notice that there's use of forced Optional unwrapping. 
 This is potentially hazardous. Here's a version that deals with Optional values safely.
 Having to 'reduce' Optional Strings adds significant complexity.

diff --git a/gistfile1.swift → encrypt_xor1.swift b/gistfile1.swift → encrypt_xor1.swift
diff --git a/encrypt_xor2.swift b/encrypt_xor2.swift
@@ -0,0 +1,52 @@
+/*
+In the version above you'll notice that there's use of forced Optional unwrapping. 
+This is potentially hazardous. Here's a version that deals with Optional values safely.
+Having to 'reduce' Optional Strings adds significant complexity.
+Below, I've shown 2 ways of dealing with this (Monadic bind & 'if let' syntax).
+*/
+
+import Foundation
+
+// Monadic bind for Optionals
+infix operator >>= {associativity left}
+func >>= <A,B> (m: A?, f: A -> B?) -> B? {
+    if let x = m {return f(x)}
+    return .None
+}
+
+extension Character {
+    func utf8() -> UInt8 {
+        let utf8 = String(self).utf8
+        return utf8[utf8.startIndex]
+    }
+}
+
+func encrypt(key:Character, c:Character) -> String? {
+    let byte = [key.utf8() ^ c.utf8()]
+    return String(bytes: byte, encoding: NSUTF8StringEncoding)
+}
+
+// Curried func for convenient use with map
+func encryptKey(key:String)(message:String) -> String? {
+    return reduce(zip(key, message), Optional("")) { str, c in str >>= { s in encrypt(c).map {s + $0} }}
+}
+
+
+let message = "Hello world!"
+let secretKey = "(:.,?P!9@PAz" // really should be randomly generated!
+let encryptedMessage = encryptKey(secretKey)(message: message) // > .Some("`_B@PpVV2<%[")
+
+// As the encryptKey func is curried it can be passed directly to map
+let decryptedMessage = encryptedMessage.map(encryptKey(secretKey)) // > .Some("Hello world!")
+
+
+/* here's how the encrypt function would look like using 'if let' syntax
+
+func encryptKey_if_let(key:String)(message:String) -> String? {
+    return reduce(zip(key, message), Optional("")) { if let str = $0, c = encrypt($1) {
+        return str + c
+    } else {
+        return .None}
+    }
+}
+*/
diff --git a/gistfile1.swift b/gistfile1.swift
@@ -1,3 +1,5 @@
+import Foundation
+
 extension Character {
     func utf8() -> UInt8 {
         let utf8 = String(self).utf8

diff --git a/gistfile1.swift b/gistfile1.swift
@@ -5,8 +5,8 @@ extension Character {
     }
 }
 
-func encrypt(s:Character, key:Character) -> String {
-    let byte = [s.utf8() ^ key.utf8()]
+func encrypt(c:Character, key:Character) -> String {
+    let byte = [c.utf8() ^ key.utf8()]
     return String(bytes: byte, encoding: NSUTF8StringEncoding)!
 }
 

diff --git a/gistfile1.swift b/gistfile1.swift
@@ -0,0 +1,20 @@
+extension Character {
+    func utf8() -> UInt8 {
+        let utf8 = String(self).utf8
+        return utf8[utf8.startIndex]
+    }
+}
+
+func encrypt(s:Character, key:Character) -> String {
+    let byte = [s.utf8() ^ key.utf8()]
+    return String(bytes: byte, encoding: NSUTF8StringEncoding)!
+}
+
+func encrypt(message:String, #key:String) -> String {
+    return reduce(Zip2(message, key), "") { $0 + encrypt($1) }
+}
+
+let message = "Hello world!"
+let secretKey = "(:.,?P!9@PAz" // really should be randomly generated!
+let encryptedMessage = encrypt(message, key: secretKey) // > "`_B@PpVV2<%["
+let decryptedMessage = encrypt(encryptedMessage, key: secretKey) // > "Hello world!"