Data commit

Task/Caesar-cipher/Dart/caesar-cipher.dart

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+class Caesar {
+  int _key;
+
+  Caesar(this._key);
+
+  int _toCharCode(String s) {
+    return s.charCodeAt(0);
+  }
+
+  String _fromCharCode(int ch) {
+    return new String.fromCharCodes([ch]);
+  }
+
+  String _process(String msg, int offset) {
+    StringBuffer sb=new StringBuffer();
+    for(int i=0;i<msg.length;i++) {
+      int ch=msg.charCodeAt(i);
+      if(ch>=_toCharCode('A')&&ch<=_toCharCode('Z')) {
+        sb.add(_fromCharCode(_toCharCode("A")+(ch-_toCharCode("A")+offset)%26));
+      }
+      else if(ch>=_toCharCode('a')&&ch<=_toCharCode('z')) {
+        sb.add(_fromCharCode(_toCharCode("a")+(ch-_toCharCode("a")+offset)%26));
+      } else {
+        sb.add(msg[i]);
+      }
+    }
+    return sb.toString();
+  }
+
+  String encrypt(String msg) {
+    return _process(msg, _key);
+  }
+
+  String decrypt(String msg) {
+    return _process(msg, 26-_key);
+   }
+}
+
+void trip(String msg) {
+  Caesar cipher=new Caesar(10);
+
+  String enc=cipher.encrypt(msg);
+  String dec=cipher.decrypt(enc);
+  print("\"$msg\" encrypts to:");
+  print("\"$enc\" decrypts to:");
+  print("\"$dec\"");
+  Expect.equals(msg,dec);
+}
+
+main() {
+  Caesar c2=new Caesar(2);
+  print(c2.encrypt("HI"));
+  Caesar c20=new Caesar(20);
+  print(c20.encrypt("HI"));
+
+  // try a few roundtrips
+
+  trip("");
+  trip("A");
+  trip("z");
+  trip("Caesar cipher");
+  trip(".-:/\"\\!");
+  trip("The Quick Brown Fox Jumps Over The Lazy Dog.");
+}