From a509a61bfbecefb09765af9e40fef9ea8c064537 Mon Sep 17 00:00:00 2001
From: Stefano Sanfilippo <a.little.coder@gmail.com>
Date: Thu, 5 Mar 2015 22:30:08 +0100
Subject: [PATCH] Adding Scope lookup utility class.

---
 Scope.hpp | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)
 create mode 100644 Scope.hpp

diff --git a/Scope.hpp b/Scope.hpp
new file mode 100644
index 0000000..a5a657f
--- /dev/null
+++ b/Scope.hpp
@@ -0,0 +1,47 @@
+#ifndef SCOPE_HPP
+#define SCOPE_HPP
+
+#include <boost/optional.hpp>
+#include <boost/range/adaptor/reversed.hpp>
+
+#include <vector>
+#include <unordered_map>
+
+
+namespace monicelli {
+
+template<class Key, class Value>
+class Scope {
+public:
+    boost::optional<Value> lookup(Key name) {
+        for (auto const& table: boost::adaptors::reverse(tables)) {
+            auto result = table.find(name);
+            if (result != table.end()) {
+                return result->second;
+            }
+        }
+
+        return boost::none;
+    }
+
+    void push(Key const& key, Value const& value) {
+        tables.back().insert({key, value});
+    }
+
+    void enter() {
+        tables.emplace_back();
+    }
+
+    void leave() {
+        if (!tables.empty()) {
+            tables.pop_back();
+        }
+    }
+
+private:
+    std::vector<std::unordered_map<Key, Value>> tables;
+};
+
+}
+
+#endif