dpwright · September 6, 2013 15:35 · Sep 6, 2013
diff --git a/maybem.cpp b/maybem.cpp
@@ -0,0 +1,49 @@
+#include <iostream>
+#include <cassert>
+#include <cmath>
+
+using namespace std;
+
+template<typename a> class Maybe
+{
+        public:
+                static Maybe<a> Just(a value) { return Maybe(value); }
+                static Maybe<a> Nothing()     { return Maybe(); }
+
+                bool isJust() { return m_valid; }
+                a getJust() { assert(isJust()); return m_value; }
+
+                template<typename b> Maybe<b> operator>>=(Maybe<b> (*f)(int)) {
+                        return isJust() ? f(getJust()) : Maybe<b>::Nothing();
+                }
+
+                Maybe<a> unit(a value) { return Maybe(value); }
+
+                void show() {
+                        if(isJust())
+                                cout << "Just " << getJust() << endl;
+                        else
+                                cout << "Nothing" << endl;
+                }
+
+        private:
+                Maybe() : m_value(0), m_valid(false) {}
+                Maybe(a value) : m_value(value), m_valid(true) {}
+                a m_value;
+                bool m_valid;
+};
+
+Maybe<int> IM_Square(int a) { return (abs(a) >= 0x8000) ? Maybe<int>::Nothing() : Maybe<int>::Just(a * a); }
+
+int main(int argc, char** argv)
+{
+        Maybe<int> result = Maybe<int>::Nothing();
+
+        result = Maybe<int>::Just(0x4000) >>= IM_Square;
+        result.show();
+
+        result = (Maybe<int>::Just(0x4000) >>= IM_Square) >>= IM_Square;
+        result.show();
+
+        return 0;
+}