Move range.h to persistent-data

persistent-data/range.h

@@ -0,0 +1,49 @@
+#ifndef PERSISTENT_DATA_RANGE_H
+#define PERSISTENT_DATA_RANGE_H
+
+#include <boost/optional.hpp>
+#include <ostream>
+
+//----------------------------------------------------------------
+
+namespace base {
+	template <typename T>
+	class range {
+	public:
+		typedef boost::optional<T> maybe;
+
+		range(maybe begin = maybe(), maybe end = maybe())
+			: begin_(begin),
+			  end_(end) {
+		}
+
+		bool operator ==(range<T> const &r) const {
+			return (begin_ == r.begin_ && end_ == r.end_);
+		}
+
+		maybe begin_;
+		maybe end_;
+	};
+
+	template <typename T>
+	std::ostream &
+	operator <<(std::ostream &out, range<T> const &r) {
+		if (r.begin_)
+			out << "[" << *r.begin_;
+		else
+			out << "[-";
+
+		out << ", ";
+
+		if (r.end_)
+			out << *r.end_ << "]";
+		else
+			out << "-]";
+
+		return out;
+	}
+}
+
+//----------------------------------------------------------------
+
+#endif