diff --git a/include/type_graph.hpp b/include/type_graph.hpp
index 19cfe23..aa67388 100644
--- a/include/type_graph.hpp
+++ b/include/type_graph.hpp
@@ -93,6 +93,12 @@ public:
     back_edges_[to].push_back(from);
   }
 
+  void SetEqual(size_t u, size_t v) {
+    AddEdge(u, v);
+    AddEdge(v, u);
+    // TODO: set equality
+  }
+
   void Calculate() {
     if (is_calculated_) {
       return;
diff --git a/include/typeclass_graph.hpp b/include/typeclass_graph.hpp
index 86093c3..dc50233 100644
--- a/include/typeclass_graph.hpp
+++ b/include/typeclass_graph.hpp
@@ -1,6 +1,60 @@
 #pragma once
 
+#include <string>
+#include <unordered_map>
+
+// for calngd
+#include "utils.hpp"
+#include "interpreter_tree.hpp"
+#include "error_handling.hpp"
+
+namespace info {
+
 class TypeclassGraph {
 public:
+  struct TypeclassMethod {
+    std::string name;
+    interpreter::tokens::FunctionDeclaration* definition = nullptr;
+  };
+
+  struct ParametrizedTypeclass {
+    utils::IdType typeclass;
+    std::vector<utils::IdType> parameter_ids; // ??
+  };
+
+  struct TypeclassVertex {
+    std::vector<std::pair<std::string, std::vector<ParametrizedTypeclass>>> parameters;
+    std::vector<TypeclassMethod> methods;
+    std::vector<ParametrizedTypeclass> dependencies;
+    interpreter::tokens::TypeclassDefinitionStatement* definition = nullptr;
+  };
+
+  utils::IdType AddTypeclass(const TypeclassVertex& typeclass) { // TODO: universal reference
+    for (auto& method : typeclass.methods) {
+      if (method_to_typeclass_.count(method.name) != 0) {
+        error_handling::HandleTypecheckError("");
+      }
+    }
+    for (auto& method : typeclass.methods) {
+      method_to_typeclass_[method.name] = typeclasses_.size();
+    }
+    typeclasses_.push_back(typeclass);
+    return typeclasses_.size() - 1;
+  }
+  std::optional<utils::IdType> FindMethodTypeclass(const std::string& name) {
+    auto method_iter = method_to_typeclass_.find(name);
+    if (method_iter == method_to_typeclass_.end()) {
+      return std::nullopt;
+    }
+    return method_iter->second;
+  }
+
+  const TypeclassVertex& GetTypeclass(utils::IdType id) {
+    return typeclasses_.at(id);
+  }
 private:
+  std::unordered_map<std::string, utils::IdType> method_to_typeclass_;
+  std::vector<TypeclassVertex> typeclasses_;
 };
+
+} // namespace info
diff --git a/include/utils.hpp b/include/utils.hpp
index 4ebcef7..2fb62ae 100644
--- a/include/utils.hpp
+++ b/include/utils.hpp
@@ -1,12 +1,13 @@
 #pragma once
 
-#include <endian.h>
 #include <vector>
 #include <unordered_map>
 
 namespace utils {
 
-using IdType = std::size_t;
+using std::size_t;
+
+using IdType = size_t;
 
 enum class ReferenceType { Reference, UniqueReference };
 
@@ -39,4 +40,42 @@ private:
   std::unordered_map<T, IdType> value_to_id_;
 };
 
+class Union { // TODO: recall right algorithm name
+public:
+  Union(size_t n) {
+    edges_.resize(n);
+    ranks_.resize(n);
+
+    for (size_t i = 0; i < n; ++i) {
+      edges_[i] = i;
+      ranks_[i] = 1;
+    }
+  }
+
+  void Connect(size_t u, size_t v) { // TODO: recall choice algorithm
+    u = GetRoot(u);
+    v = GetRoot(v);
+    if (ranks_[v] >= ranks_[u]) {
+      edges_[u] = v;
+      ranks_[v] = std::max(ranks_[u] + 1, ranks_[v]);
+    } else {
+      edges_[v] = u;
+    }
+  }
+
+  bool IsConnected(size_t u, size_t v) {
+    return GetRoot(u) == GetRoot(v);
+  }
+
+  size_t GetRoot(size_t v) {
+    if (edges_[v] == v) {
+      return v;
+    }
+    return edges_[v] = GetRoot(edges_[v]);
+  }
+private:
+  std::vector<size_t> edges_;
+  std::vector<size_t> ranks_;
+};
+
 } // namespace utils