Implementing Xor operation

main/src/com/google/refine/expr/functions/booleans/Xor.java

@@ -0,0 +1,42 @@
+/*
+  Implementing a naive XOR operation
+  Copyright 2013, Jesus M. Castagnetto
+  License: BSD 2-Clause License (http://opensource.org/licenses/BSD-2-Clause)
+*/
+
+package com.google.refine.expr.functions.booleans;
+
+import java.util.Properties;
+
+import org.json.JSONException;
+import org.json.JSONWriter;
+
+import com.google.refine.expr.EvalError;
+import com.google.refine.grel.ControlFunctionRegistry;
+import com.google.refine.grel.Function;
+
+public class Xor implements Function {
+
+    @Override
+    public Object call(Properties bindings, Object[] args) {
+        if (args.length == 2 &&
+            args[0] != null && args[0] instanceof Boolean &&
+            args[1] != null && args[0] instanceof Boolean) {
+            boolean o1 = ((Boolean) args[0]).booleanValue();
+            boolean o2 = ((Boolean) args[1]).booleanValue();
+            return o1 != o2;
+        }
+        return new EvalError(ControlFunctionRegistry.getFunctionName(this) + " expects 2 booleans");
+    }
+    
+    @Override
+    public void write(JSONWriter writer, Properties options)
+            throws JSONException {
+        
+        writer.object();
+        writer.key("description"); writer.value("XORs two boolean values");
+        writer.key("params"); writer.value("boolean a, boolean b");
+        writer.key("returns"); writer.value("boolean");
+        writer.endObject();
+    }
+}