initial commit

src/util/Nullable.h

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+// Copyright 2017, University of Freiburg,
+// Chair of Algorithms and Data Structures.
+// Authors: Patrick Brosi <brosi@informatik.uni-freiburg.de>
+
+#ifndef UTIL_NULLABLE_H_
+#define UTIL_NULLABLE_H_
+
+namespace util {
+
+template<typename T>
+class Nullable {
+ public:
+  Nullable()
+   : val(), null(true) {}
+  Nullable(T* valPointer)
+   : val(), null(true) {
+   if (valPointer) {
+     assign(*valPointer);
+   }
+  }
+  Nullable(const T& value)
+   : val(value), null(false) {}
+  Nullable(const Nullable& other)
+   : val(other.val), null(other.isNull()) {}
+
+  Nullable& operator=(const Nullable& other) {
+    val = other.get();
+    null = other.isNull();
+    return *this;
+  }
+
+  T operator=(const T& other) {
+    assign(other);
+    return val;
+  }
+
+  /**
+   * Passing through comparision operators
+   */
+
+  bool operator==(const Nullable& other) const {
+    return (other.isNull() && isNull()) || other.get() == get();
+  }
+
+  bool operator!=(const Nullable& other) const {
+    return !(*this == other);
+  }
+
+  bool operator<(const Nullable& other) const {
+    return !other.isNull() && !isNull() && get() < other.get();
+  }
+
+  bool operator>(const Nullable& other) const {
+    return !(*this < other || *this == other);
+  }
+
+  bool operator<=(const Nullable& other) const {
+    return *this < other || *this == other;
+  }
+
+  bool operator>=(const Nullable& other) const {
+    return *this > other || *this == other;
+  }
+
+  bool operator==(const T& other) const {
+    return !isNull() && other == get();
+  }
+
+  bool operator!=(const T& other) const {
+    return !(*this == other);
+  }
+
+  bool operator<(const T& other) const {
+    return !isNull() && get() < other;
+  }
+
+  bool operator>(const T& other) const {
+    return !(*this < other || *this == other);
+  }
+
+  bool operator<=(const T& other) const {
+    return *this < other || *this == other;
+  }
+
+  bool operator>=(const T& other) const {
+    return *this > other || *this == other;
+  }
+
+  operator T() const {
+    return get();
+  }
+
+  bool isNull() const {
+    return null;
+  }
+
+  T get() const {
+    if (!isNull()) return val;
+    else throw std::runtime_error("Trying to retrieve value of NULL object.");
+  }
+
+private:
+  void assign(T v) {
+    val = v;
+    null = false;
+  }
+
+  T val;
+  bool null;
+};
+
+}
+
+#endif  // UTIL_NULLABLE_H_