From 131102ad6622f41719f7fc609ed1f3cf222d54d4 Mon Sep 17 00:00:00 2001
From: Danila Fedorin <danila.fedorin@gmail.com>
Date: Mon, 26 Aug 2019 00:11:38 -0700
Subject: [PATCH] Add environment code

---
 03/env.cpp | 16 ++++++++++++++++
 03/env.hpp | 16 ++++++++++++++++
 2 files changed, 32 insertions(+)
 create mode 100644 03/env.cpp
 create mode 100644 03/env.hpp

diff --git a/03/env.cpp b/03/env.cpp
new file mode 100644
index 0000000..74059a8
--- /dev/null
+++ b/03/env.cpp
@@ -0,0 +1,16 @@
+#include "env.hpp"
+
+type_ptr type_env::lookup(const std::string& name) const {
+    auto it = names.find(name);
+    if(it != names.end()) return it->second;
+    if(parent) return parent->lookup(name);
+    return nullptr;
+}
+
+void type_env::bind(const std::string& name, type_ptr t) {
+    names[name] = t;
+}
+
+type_env type_env::scope() const {
+    return type_env(this);
+}
diff --git a/03/env.hpp b/03/env.hpp
new file mode 100644
index 0000000..6470bdd
--- /dev/null
+++ b/03/env.hpp
@@ -0,0 +1,16 @@
+#pragma once
+#include <map>
+#include "type.hpp"
+
+struct type_env {
+    std::map<std::string, type_ptr> names;
+    type_env const* parent = nullptr;
+
+    type_env(type_env const* p)
+        : parent(p) {}
+    type_env() : type_env(nullptr) {}
+
+    type_ptr lookup(const std::string& name) const;
+    void bind(const std::string& name, type_ptr t);
+    type_env scope() const;
+};