diff --git a/src/common.cpp b/src/common.cpp
index f71318a..8b8f52e 100644
--- a/src/common.cpp
+++ b/src/common.cpp
@@ -187,11 +187,71 @@ short cmp_tag(Tag lhs, Tag rhs) {
 }
 
 Result<Value> Dict::get(Arena& arena, Value& key) {
-  return ErrorCode::TypeMismatch;
+  auto pos = TRY(find(arena, key));
+  if (pos > size()) return ErrorCode::KeyError;
+  auto k = TRY(Value::create(arena, _value->data[pos * 2].get(_value.get())));
+
+  if (TRY(k != key)) {
+    return ErrorCode::KeyError;
+  }
+
+  return TRY(Value::create(arena, _value->data[pos * 2 + 1].get(_value.get())));
 }
 
 Result<Dict> Dict::insert(Arena& arena, Value& key, Value& value) {
-  return ErrorCode::TypeMismatch;
+  auto pos = TRY(find(arena, key));
+  auto s = size();
+  if (pos >= s) {
+    s += 1;
+  } else {
+    auto k = TRY(Value::create(arena, _value->data[pos * 2].get(_value.get())));
+    if (TRY(k != key)) s += 1;
+  }
+
+  auto pod = TRY(arena.alloc<PodDict>(2 * s * sizeof(OffPtr<PodObject>)));
+  pod->size = s;
+
+  auto vpod = _value.get();
+  for (uint64_t i = 0, j = 0; i < s; i++, j++) {
+    if (i == pos) {
+      pod->data[i * 2] = OffPtr<PodObject>(pod, key.pod());
+      pod->data[i * 2 + 1] = OffPtr<PodObject>(pod, value.pod());
+      if (s > size() && i < s - 1) {
+        i++;
+        pod->data[i * 2] =
+            OffPtr<PodObject>(pod, _value->data[j * 2].get(vpod));
+        pod->data[i * 2 + 1] =
+            OffPtr<PodObject>(pod, _value->data[j * 2 + 1].get(vpod));
+      }
+    } else {
+      pod->data[i * 2] = OffPtr<PodObject>(pod, _value->data[j * 2].get(vpod));
+      pod->data[i * 2 + 1] =
+          OffPtr<PodObject>(pod, _value->data[j * 2 + 1].get(vpod));
+    }
+  }
+
+  return Dict(TRY(MkGcRoot(pod, arena)));
+}
+
+Result<uint64_t> Dict::find(Arena& arena, Value& key) {
+  uint64_t left = 0;
+  uint64_t right = size();
+  uint64_t pos = (left + right) / 2;
+  while (left < right) {
+    auto v = TRY(Value::create(arena, _value->data[pos * 2].get(_value.get())));
+    auto c = TRY(v.cmp(key));
+    if (c == 0) {
+      return pos;
+    }
+    if (c < 0) {
+      left = pos + 1;
+    }
+    if (c > 0) {
+      right = pos;
+    }
+    pos = (left + right) / 2;
+  }
+  return left;
 }
 
 Result<short> Int64::cmp(Float& rhs) {
diff --git a/src/common.hpp b/src/common.hpp
index 7151e3e..4b49e99 100644
--- a/src/common.hpp
+++ b/src/common.hpp
@@ -23,6 +23,7 @@ class Syntax;
 class Pair;
 class Array;
 class ByteArray;
+class Writer;
 
 short cmp_tag(Tag lhs, Tag rhs);
 
@@ -256,6 +257,7 @@ class ByteArray : public Object {
 
 class Dict : public Object {
  public:
+  friend class Writer;
   Dict() {}
   Dict(Dict&& rhs) : _value(std::move(rhs._value)) {}
   Dict(GcRoot<PodDict>&& val) : _value(std::move(val)) {}
@@ -291,6 +293,9 @@ class Dict : public Object {
 
   Result<Dict> insert(Arena& arena, Value& key, Value& value);
 
+  template <class K, class V>
+  Result<Dict> insert(Arena& arena, const K& key, const V& value);
+
   Result<Dict> concat(Arena& arena, Dict& rhs) {
     uint64_t rhs_size = rhs.size();
     uint64_t lhs_size = size();
@@ -305,6 +310,8 @@ class Dict : public Object {
   }
 
  private:
+  Result<uint64_t> find(Arena& arena, Value& key);
+
   uint64_t size() { return _value->size; }
   GcRoot<PodDict> _value;
 };
@@ -643,6 +650,10 @@ class Value {
 
   static Result<Value> create(Arena& arena, PodObject* obj);
 
+  static Result<Value> create(Arena& arena, const int64_t& value) {
+    return Value(TRY(Int64::create(arena, value)));
+  }
+
   template <class T>
   bool is() {
     return dynamic_cast<T*>((Object*)buf) != nullptr;
@@ -664,6 +675,7 @@ class Value {
   }
 
   Result<bool> operator==(Value& rhs) { return TRY(cmp(rhs)) == 0; }
+  Result<bool> operator!=(Value& rhs) { return TRY(cmp(rhs)) != 0; }
 
   Result<Value> copy(Arena& arena) { return ((Object*)buf)->copy(arena); }
 
@@ -676,3 +688,11 @@ Result<Value> syntax_unwrap(Value& val);
 Result<Value> reverse(Arena& arena, Value& val);
 
 Result<void> debug_print(Arena& arena, String& val);
+
+template <class K, class V>
+Result<Dict> Dict::insert(Arena& arena, const K& key, const V& value) {
+  Value k = TRY(Value::create(arena, key));
+  Value v = TRY(Value::create(arena, value));
+
+  return insert(arena, k, v);
+}
diff --git a/src/error.hpp b/src/error.hpp
index 88e7d2c..ca1a07a 100644
--- a/src/error.hpp
+++ b/src/error.hpp
@@ -11,4 +11,5 @@ enum class ErrorCode {
   NotImplemented,
   InvalidSymbol,
   MalformedList,
+  KeyError,
 };
diff --git a/src/writer.cpp b/src/writer.cpp
index f595a74..35026c8 100644
--- a/src/writer.cpp
+++ b/src/writer.cpp
@@ -190,5 +190,29 @@ Result<String> Writer::write_array(Array& val) {
 }
 
 Result<String> Writer::write_dict(Dict& val) {
-  return ErrorCode::NotImplemented;
+  String res = TRY(String::create(_arena, "{"));
+
+  bool is_first = true;
+  for (uint64_t i = 0; i < val.size(); i++) {
+    Value k = TRY(
+        Value::create(_arena, val._value->data[i * 2].get(val._value.get())));
+
+    Value v = TRY(Value::create(
+        _arena, val._value->data[i * 2 + 1].get(val._value.get())));
+
+    if (!is_first) res = TRY(res.concat(_arena, " "));
+
+    String first_str = TRY(write_one(k));
+    res = TRY(res.concat(_arena, first_str));
+
+    res = TRY(res.concat(_arena, " "));
+
+    String second_str = TRY(write_one(v));
+    res = TRY(res.concat(_arena, second_str));
+
+    is_first = false;
+  }
+
+  res = TRY(res.concat(_arena, "}"));
+  return res;
 }
diff --git a/test/dict.cpp b/test/dict.cpp
index d92f128..38a410f 100644
--- a/test/dict.cpp
+++ b/test/dict.cpp
@@ -1,4 +1,24 @@
+#include "common.hpp"
 #include "die.hpp"
 #include "test.hpp"
+#include "writer.hpp"
 
-TEST_CASE(dict_insert) { die("test"); }
+StaticArena<64 * 1024 * 1024> arena;
+
+TEST_CASE(dict_insert) {
+  auto d = DIEX(Dict::create(arena));
+
+  d = DIEX(d.insert(arena, 1, 2));
+  d = DIEX(d.insert(arena, 1, 3));
+  d = DIEX(d.insert(arena, 3, 3));
+  d = DIEX(d.insert(arena, 0, 4));
+  d = DIEX(d.insert(arena, 0, 5));
+  d = DIEX(d.insert(arena, 2, 6));
+
+  auto w = Writer(arena);
+
+  auto dd = DIEX(d.copy(arena));
+  auto s = DIEX(w.write_one(dd));
+
+  DIEX(debug_print(arena, s));
+}