diff --git a/doc/Literals.md b/doc/Literals.md
index 4ba32589..a7ee42b4 100644
--- a/doc/Literals.md
+++ b/doc/Literals.md
@@ -16,7 +16,9 @@ This page explains literals.
 
     boolean: 'true' | 'false' ;
 
-`null` and `false` are falsy. The other values are all truthy.
+`false` is an alias for `null`.
+The only falsy value is `null`. The other values are all truthy.
+`true` is the value that is just truthy.
 
 ## Integer Literals
 
diff --git a/doc/StackUsage.md b/doc/StackUsage.md
index cb5a4955..ba66b8d4 100644
--- a/doc/StackUsage.md
+++ b/doc/StackUsage.md
@@ -104,7 +104,7 @@
     NUL
         |
         |N
-    BOOLEAN
+    TRUE
         |
         |B
     INTEGER
diff --git a/doc/TermExpressions.md b/doc/TermExpressions.md
index f2396eea..87e3ca35 100644
--- a/doc/TermExpressions.md
+++ b/doc/TermExpressions.md
@@ -10,7 +10,7 @@ See [PrimaryExpressions](PrimaryExpressions.md).
 
     unary: ('+' | '-' | '!' | '~')* primary ;
 
-Negate operator (`!`) returns `true` if the operand is falsy, returns `false` otherwise.
+Negate operator (`!`) returns `true` if the operand is `false` (`null`), returns `false` (`null`) otherwise.
 
 ## Multiplicative Expressions
 
@@ -28,7 +28,7 @@ Negate operator (`!`) returns `true` if the operand is falsy, returns `false` ot
 
     relational: shift (('<' | '>' | '<=' | '>=') shift)* ;
 
-Relational, equality, and identity operators return either `true` or `false`.
+Relational, equality, and identity operators return either `true` or `false` (`null`).
 
 ## Equality Expressions
 
@@ -42,7 +42,7 @@ Relational, equality, and identity operators return either `true` or `false`.
 
     and: identity ('&' identity)* ;
 
-Bitwise operators (`&`, `^`, and `|`) do bitwise operations if both the operands are integers, do boolean operations if both the operands are booleans, throws an exception otherwise.
+Bitwise operators (`&`, `^`, and `|`) do bitwise operations if both the operands are integers, do boolean operations if the left operand is boolean (`true`, `false`, or `null`), throws an exception otherwise.
 
 ## Xor Expressions
 
@@ -56,13 +56,13 @@ Bitwise operators (`&`, `^`, and `|`) do bitwise operations if both the operands
 
     and_also: or ('&&' or)* ;
 
-Evaluates the left operand, returns it if it is falsy, evaluates the right operand and returns it otherwise.
+Evaluates the left operand, returns it if it is `false` (`null`), evaluates the right operand and returns it otherwise.
 
 ## Or Else Expressions
 
     or_else: and_also ('||' and_also)* ;
 
-Evaluates the left operand, returns it if it is truthy, evaluates the right operand and returns it otherwise.
+Evaluates the left operand, returns it if it is not `false` (`null`), evaluates the right operand and returns it otherwise.
 
 ## Conditional Expressions
 
diff --git a/doc/WalkThrough.md b/doc/WalkThrough.md
index 6aebfdac..3c965b58 100644
--- a/doc/WalkThrough.md
+++ b/doc/WalkThrough.md
@@ -13,7 +13,7 @@ This document walks through xemmai language.
     "This is a string."
     null
     true
-    false
+    false # => null
 
 ## Variables
 
diff --git a/include/xemmai/ast.h b/include/xemmai/ast.h
index 2a536ad3..9d0d6a60 100644
--- a/include/xemmai/ast.h
+++ b/include/xemmai/ast.h
@@ -72,32 +72,22 @@ struct t_operand
 		e_tag__TEMPORARY
 	};
 
-	static inline const t_pvalue v_null{};
-	static inline const t_pvalue v_true{true};
-	static inline const t_pvalue v_false{false};
-
 	t_tag v_tag;
 	union
 	{
 		intptr_t v_integer;
 		double v_float;
-		const t_pvalue* v_value;
+		t_object* v_value;
 		size_t v_index;
 	};
 
-	t_operand(nullptr_t) : v_tag(e_tag__LITERAL), v_value(&v_null)
-	{
-	}
-	t_operand(bool a_value) : v_tag(e_tag__LITERAL), v_value(a_value ? &v_true : &v_false)
-	{
-	}
 	t_operand(intptr_t a_value) : v_tag(e_tag__INTEGER), v_integer(a_value)
 	{
 	}
 	t_operand(double a_value) : v_tag(e_tag__FLOAT), v_float(a_value)
 	{
 	}
-	t_operand(t_svalue& a_value) : v_tag(e_tag__LITERAL), v_value(reinterpret_cast<const t_pvalue*>(&a_value))
+	t_operand(t_object* a_value) : v_tag(e_tag__LITERAL), v_value(a_value)
 	{
 	}
 	t_operand() : v_tag(e_tag__TEMPORARY)
@@ -418,11 +408,16 @@ struct t_super : t_node
 	virtual t_operand f_emit(t_emit& a_emit, bool a_tail, bool a_operand, bool a_clear);
 };
 
-struct t_null : t_node
+struct t_boolean : t_node
 {
-	using t_node::t_node;
+	bool v_value;
+
+	t_boolean(const t_at& a_at, bool a_value = false) : t_node(a_at), v_value(a_value)
+	{
+	}
 	virtual t_operand f_emit(t_emit& a_emit, bool a_tail, bool a_operand, bool a_clear);
 };
+using t_null = t_boolean;
 
 template<typename T>
 struct t_literal : t_node
@@ -569,11 +564,6 @@ struct XEMMAI__LOCAL t_emit
 		v_code->v_instructions.push_back(reinterpret_cast<void*>(a_operand));
 		return *this;
 	}
-	t_emit& operator<<(bool a_operand)
-	{
-		v_code->v_instructions.push_back(reinterpret_cast<void*>(a_operand ? 1 : 0));
-		return *this;
-	}
 	t_emit& operator<<(double a_operand)
 	{
 		union
@@ -585,14 +575,9 @@ struct XEMMAI__LOCAL t_emit
 		for (size_t i = 0; i < sizeof(double) / sizeof(void*); ++i) v_code->v_instructions.push_back(v1[i]);
 		return *this;
 	}
-	t_emit& operator<<(const t_pvalue& a_operand)
+	t_emit& operator<<(t_object* a_operand)
 	{
-		v_code->v_instructions.push_back(const_cast<t_pvalue*>(&a_operand));
-		return *this;
-	}
-	t_emit& operator<<(t_svalue& a_operand)
-	{
-		v_code->v_instructions.push_back(&a_operand);
+		v_code->v_instructions.push_back(a_operand);
 		return *this;
 	}
 	t_emit& operator<<(t_label& a_label)
@@ -637,11 +622,6 @@ struct XEMMAI__LOCAL t_emit
 	}
 };
 
-template<>
-constexpr t_instruction t_emit::f_instruction_of<bool>()
-{
-	return e_instruction__BOOLEAN;
-}
 template<>
 constexpr t_instruction t_emit::f_instruction_of<intptr_t>()
 {
@@ -663,7 +643,7 @@ t_operand t_literal<T>::f_emit(t_emit& a_emit, bool a_tail, bool a_operand, bool
 	if (a_clear) return {};
 	if (a_tail) {
 		a_emit.f_emit_safe_point(this);
-		a_emit << static_cast<t_instruction>(t_emit::f_instruction_of<T>() + e_instruction__RETURN_BOOLEAN - e_instruction__BOOLEAN) << v_value;
+		a_emit << static_cast<t_instruction>(t_emit::f_instruction_of<T>() + e_instruction__RETURN_NUL - e_instruction__NUL) << v_value;
 	} else {
 		a_emit << t_emit::f_instruction_of<T>() << a_emit.v_stack << v_value;
 	}
diff --git a/include/xemmai/boolean.h b/include/xemmai/boolean.h
index 4b264837..a2cf5b6d 100644
--- a/include/xemmai/boolean.h
+++ b/include/xemmai/boolean.h
@@ -14,7 +14,7 @@ struct t_type_of<bool> : t_uninstantiatable<t_bears<bool>>
 	{
 		static bool f_as(auto&& a_object)
 		{
-			return a_object && (a_object.f_tag() != e_tag__BOOLEAN || a_object.f_boolean());
+			return a_object;
 		}
 		static bool f_is(t_object* a_object)
 		{
@@ -24,11 +24,7 @@ struct t_type_of<bool> : t_uninstantiatable<t_bears<bool>>
 
 	static t_object* f__string(bool a_self)
 	{
-		return t_string::f_instantiate(a_self ? L"true"sv : L"false"sv);
-	}
-	static intptr_t f__hash(bool a_self)
-	{
-		return a_self ? 1 : 0;
+		return t_string::f_instantiate(a_self ? L"true"sv : L"null"sv);
 	}
 	XEMMAI__LOCAL static void f_define();
 
diff --git a/include/xemmai/code.h b/include/xemmai/code.h
index 1024d137..e877f7e4 100644
--- a/include/xemmai/code.h
+++ b/include/xemmai/code.h
@@ -40,12 +40,12 @@ enum t_instruction
 	e_instruction__CLASS,
 	e_instruction__SUPER,
 	e_instruction__NUL,
-	e_instruction__BOOLEAN,
+	e_instruction__TRU,
 	e_instruction__INTEGER,
 	e_instruction__FLOAT,
 	e_instruction__INSTANCE,
 	e_instruction__RETURN_NUL,
-	e_instruction__RETURN_BOOLEAN,
+	e_instruction__RETURN_TRU,
 	e_instruction__RETURN_INTEGER,
 	e_instruction__RETURN_FLOAT,
 	e_instruction__RETURN_INSTANCE,
diff --git a/include/xemmai/fiber.h b/include/xemmai/fiber.h
index b3915da5..6206a3d7 100644
--- a/include/xemmai/fiber.h
+++ b/include/xemmai/fiber.h
@@ -265,7 +265,7 @@ inline t_pvalue t_value<T_tag>::f_##a_name() const\
 	auto p = static_cast<t_object*>(*this);\
 	switch (reinterpret_cast<uintptr_t>(p)) {\
 	case e_tag__NULL:\
-	case e_tag__BOOLEAN:\
+	case e_tag__TRUE:\
 		f_throw(L"not supported."sv);\
 	case e_tag__INTEGER:\
 		return a_operator(v_integer);\
@@ -287,7 +287,7 @@ inline t_pvalue t_value<T_tag>::f_complement() const
 	case e_tag__INTEGER:
 		return ~v_integer;
 	case e_tag__NULL:
-	case e_tag__BOOLEAN:
+	case e_tag__TRUE:
 	case e_tag__FLOAT:
 		f_throw(L"not supported."sv);
 	default:
diff --git a/include/xemmai/float.h b/include/xemmai/float.h
index 7c05867e..35d2ee0a 100644
--- a/include/xemmai/float.h
+++ b/include/xemmai/float.h
@@ -42,7 +42,7 @@ struct t_type_of<double> : t_derivable<t_bears<double>, t_derived_primitive<doub
 			if (!std::is_same_v<typename t_fundamental<T>::t_type, double>) return reinterpret_cast<uintptr_t>(a_object) >= e_tag__OBJECT && a_object->f_type()->f_derives<typename t_fundamental<T>::t_type>();
 			switch (reinterpret_cast<uintptr_t>(a_object)) {
 			case e_tag__NULL:
-			case e_tag__BOOLEAN:
+			case e_tag__TRUE:
 				return false;
 			case e_tag__INTEGER:
 			case e_tag__FLOAT:
diff --git a/include/xemmai/global.h b/include/xemmai/global.h
index 026d5011..bb6a2940 100644
--- a/include/xemmai/global.h
+++ b/include/xemmai/global.h
@@ -4,7 +4,6 @@
 #include "engine.h"
 #include "native.h"
 #include "method.h"
-#include "null.h"
 #include "list.h"
 #include "map.h"
 #include "bytes.h"
@@ -39,7 +38,6 @@ class t_global : public t_library
 	t_slot_of<t_type> v_type_advanced_lambda_shared;
 	t_slot_of<t_type> v_type_method;
 	t_slot_of<t_type> v_type_throwable;
-	t_slot_of<t_type> v_type_null;
 	t_slot_of<t_type> v_type_boolean;
 	t_slot_of<t_type> v_type_integer;
 	t_slot_of<t_type> v_type_float;
@@ -216,7 +214,6 @@ XEMMAI__LIBRARY__TYPE_AS(t_global, t_advanced_lambda<t_lambda>, advanced_lambda)
 XEMMAI__LIBRARY__TYPE_AS(t_global, t_advanced_lambda<t_lambda_shared>, advanced_lambda_shared)
 XEMMAI__LIBRARY__TYPE(t_global, method)
 XEMMAI__LIBRARY__TYPE(t_global, throwable)
-XEMMAI__LIBRARY__TYPE_AS(t_global, std::nullptr_t, null)
 XEMMAI__LIBRARY__TYPE_AS(t_global, bool, boolean)
 XEMMAI__LIBRARY__TYPE_AS(t_global, intptr_t, integer)
 XEMMAI__LIBRARY__TYPE_AS(t_global, double, float)
@@ -244,8 +241,7 @@ XEMMAI__PORTABLE__ALWAYS_INLINE inline t_type* t_value<T_tag>::f_type() const
 	auto p = static_cast<t_object*>(*this);
 	switch (reinterpret_cast<uintptr_t>(p)) {
 	case e_tag__NULL:
-		return f_global()->f_type<std::nullptr_t>();
-	case e_tag__BOOLEAN:
+	case e_tag__TRUE:
 		return f_global()->f_type<bool>();
 	case e_tag__INTEGER:
 		return f_global()->f_type<intptr_t>();
@@ -281,9 +277,8 @@ inline t_pvalue t_value<T_tag>::f_##a_name() const\
 	auto p = static_cast<t_object*>(*this);\
 	switch (reinterpret_cast<uintptr_t>(p)) {\
 	case e_tag__NULL:\
-		return t_type_of<std::nullptr_t>::f__##a_name(*this);\
-	case e_tag__BOOLEAN:\
-		return t_type_of<bool>::f__##a_name(v_boolean);\
+	case e_tag__TRUE:\
+		return t_type_of<bool>::f__##a_name(*this);\
 	case e_tag__INTEGER:\
 		return t_type_of<intptr_t>::f__##a_name(v_integer);\
 	case e_tag__FLOAT:\
@@ -315,7 +310,7 @@ inline t_pvalue t_value<T_tag>::f_##a_name(const t_pvalue& a_value) const\
 	auto p = static_cast<t_object*>(*this);\
 	switch (reinterpret_cast<uintptr_t>(p)) {\
 	case e_tag__NULL:\
-	case e_tag__BOOLEAN:\
+	case e_tag__TRUE:\
 		f_throw(L"not supported."sv);\
 	case e_tag__INTEGER:\
 		return t_type_of<intptr_t>::f__##a_name(v_integer, a_value);\
@@ -336,7 +331,7 @@ inline t_pvalue t_value<T_tag>::f_##a_name(const t_pvalue& a_value) const\
 		f_check<intptr_t>(a_value, L"argument0");\
 		return static_cast<uintptr_t>(v_integer) a_operator f_as<intptr_t>(a_value);\
 	case e_tag__NULL:\
-	case e_tag__BOOLEAN:\
+	case e_tag__TRUE:\
 	case e_tag__FLOAT:\
 		f_throw(L"not supported."sv);\
 	default:\
@@ -350,9 +345,8 @@ inline t_pvalue t_value<T_tag>::f_##a_name(const t_pvalue& a_value) const\
 	auto p = static_cast<t_object*>(*this);\
 	switch (reinterpret_cast<uintptr_t>(p)) {\
 	case e_tag__NULL:\
+	case e_tag__TRUE:\
 		return a_operator(p == a_value.v_p);\
-	case e_tag__BOOLEAN:\
-		return a_operator(p == a_value.v_p && v_boolean == a_value.v_boolean);\
 	case e_tag__INTEGER:\
 		return t_type_of<intptr_t>::f__##a_name(v_integer, a_value);\
 	case e_tag__FLOAT:\
@@ -367,13 +361,12 @@ inline t_pvalue t_value<T_tag>::f_##a_name(const t_pvalue& a_value) const\
 {\
 	auto p = static_cast<t_object*>(*this);\
 	switch (reinterpret_cast<uintptr_t>(p)) {\
-	case e_tag__BOOLEAN:\
-		if (a_value.f_tag() != e_tag__BOOLEAN) [[unlikely]] f_throw_type_error<bool>(L"argument0");\
-		return v_boolean a_operator a_value.v_boolean;\
+	case e_tag__NULL:\
+	case e_tag__TRUE:\
+		return static_cast<bool>(static_cast<bool>(p) a_operator f_as<bool>(a_value));\
 	case e_tag__INTEGER:\
 		f_check<intptr_t>(a_value, L"argument0");\
 		return v_integer a_operator f_as<intptr_t>(a_value);\
-	case e_tag__NULL:\
 	case e_tag__FLOAT:\
 		f_throw(L"not supported."sv);\
 	default:\
diff --git a/include/xemmai/integer.h b/include/xemmai/integer.h
index 6ab095b7..9ce7a399 100644
--- a/include/xemmai/integer.h
+++ b/include/xemmai/integer.h
@@ -38,7 +38,7 @@ struct t_type_of<intptr_t> : t_derivable<t_bears<intptr_t>, t_derived_primitive<
 			case e_tag__INTEGER:
 				return true;
 			case e_tag__NULL:
-			case e_tag__BOOLEAN:
+			case e_tag__TRUE:
 			case e_tag__FLOAT:
 				return false;
 			default:
diff --git a/include/xemmai/module.h b/include/xemmai/module.h
index 5bdaca8f..39fe3285 100644
--- a/include/xemmai/module.h
+++ b/include/xemmai/module.h
@@ -42,20 +42,19 @@ struct t_module
 struct t_script : t_module::t_body
 {
 	std::wstring v_path;
-	std::deque<t_svalue> v_slots;
+	std::deque<t_slot> v_slots;
 	std::mutex v_mutex;
 
 	t_script(std::wstring_view a_path) : v_path(a_path)
 	{
 	}
 	virtual void f_scan(t_scan a_scan);
-	t_svalue& f_slot(t_object* a_p)
+	t_object* f_slot(t_object* a_p)
 	{
 		v_mutex.lock();
 		auto& p = v_slots.emplace_back();
 		v_mutex.unlock();
-		p = a_p;
-		return p;
+		return p = a_p;
 	}
 };
 
diff --git a/include/xemmai/null.h b/include/xemmai/null.h
deleted file mode 100644
index 3a64e2b0..00000000
--- a/include/xemmai/null.h
+++ /dev/null
@@ -1,23 +0,0 @@
-#ifndef XEMMAI__NULL_H
-#define XEMMAI__NULL_H
-
-#include "string.h"
-
-namespace xemmai
-{
-
-template<>
-struct t_type_of<std::nullptr_t> : t_uninstantiatable<t_bears<std::nullptr_t>>
-{
-	static t_object* f__string(const t_pvalue&)
-	{
-		return t_string::f_instantiate(L"null"sv);
-	}
-	XEMMAI__LOCAL static void f_define();
-
-	using t_base::t_base;
-};
-
-}
-
-#endif
diff --git a/include/xemmai/object.h b/include/xemmai/object.h
index d440c1dc..9aa50865 100644
--- a/include/xemmai/object.h
+++ b/include/xemmai/object.h
@@ -356,7 +356,7 @@ struct t_type::t_cast<T*>
 		switch (reinterpret_cast<uintptr_t>(a_object)) {
 		case e_tag__NULL:
 			return true;
-		case e_tag__BOOLEAN:
+		case e_tag__TRUE:
 		case e_tag__INTEGER:
 		case e_tag__FLOAT:
 			return false;
diff --git a/include/xemmai/parser.h b/include/xemmai/parser.h
index eb0ce1b6..c364f727 100644
--- a/include/xemmai/parser.h
+++ b/include/xemmai/parser.h
@@ -30,7 +30,7 @@ class XEMMAI__LOCAL t_parser
 	{
 		f_throw(a_message, v_lexer.f_at());
 	}
-	t_svalue& f_symbol() const
+	t_object* f_symbol() const
 	{
 		return v_module.f_slot(t_symbol::f_instantiate(v_lexer.f_value()));
 	}
diff --git a/include/xemmai/value.h b/include/xemmai/value.h
index ba087d73..5a963e49 100644
--- a/include/xemmai/value.h
+++ b/include/xemmai/value.h
@@ -21,7 +21,7 @@ using t_type = t_type_of<t_object>;
 enum t_tag
 {
 	e_tag__NULL,
-	e_tag__BOOLEAN,
+	e_tag__TRUE,
 	e_tag__INTEGER,
 	e_tag__FLOAT,
 	e_tag__OBJECT
@@ -236,7 +236,6 @@ class t_value : public T_tag
 
 	union
 	{
-		bool v_boolean;
 		intptr_t v_integer;
 		double v_float;
 	};
@@ -251,7 +250,7 @@ class t_value : public T_tag
 
 public:
 	using T_tag::T_tag;
-	t_value(bool a_value) : T_tag(reinterpret_cast<t_object*>(e_tag__BOOLEAN)), v_boolean(a_value)
+	t_value(bool a_value) : T_tag(reinterpret_cast<t_object*>(a_value ? e_tag__TRUE : e_tag__NULL))
 	{
 	}
 	template<typename T, std::enable_if_t<std::is_integral_v<T>, bool> = true>
@@ -289,8 +288,6 @@ class t_value : public T_tag
 		auto p = f_tag();
 		if (p != a_value.f_tag()) return false;
 		switch (p) {
-		case e_tag__BOOLEAN:
-			return v_boolean == a_value.v_boolean;
 		case e_tag__INTEGER:
 			return v_integer == a_value.v_integer;
 		case e_tag__FLOAT:
@@ -303,10 +300,6 @@ class t_value : public T_tag
 	{
 		return reinterpret_cast<uintptr_t>(static_cast<t_object*>(*this));
 	}
-	bool f_boolean() const
-	{
-		return v_boolean;
-	}
 	intptr_t f_integer() const;
 	double f_float() const;
 	t_type_of<t_object>* f_type() const;
@@ -342,17 +335,6 @@ class t_value : public T_tag
 	t_value<t_pointer> f_set_at(const t_value<t_pointer>& a_index, const t_value<t_pointer>& a_value) const;
 	t_value<t_pointer> f_plus() const;
 	t_value<t_pointer> f_minus() const;
-	t_value<t_pointer> f_not() const
-	{
-		switch (reinterpret_cast<uintptr_t>(f_tag())) {
-		case e_tag__NULL:
-			return true;
-		case e_tag__BOOLEAN:
-			return !v_boolean;
-		default:
-			return false;
-		}
-	}
 	t_value<t_pointer> f_complement() const;
 	t_value<t_pointer> f_multiply(const t_value<t_pointer>& a_value) const;
 	t_value<t_pointer> f_divide(const t_value<t_pointer>& a_value) const;
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index d0c2fea2..f4277c0e 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -12,7 +12,6 @@ add_executable(xemmai
 	code.cc
 	lambda.cc
 	throwable.cc
-	null.cc
 	boolean.cc
 	integer.cc
 	float.cc
diff --git a/src/ast.cc b/src/ast.cc
index eb4110ad..3bb24268 100644
--- a/src/ast.cc
+++ b/src/ast.cc
@@ -717,15 +717,15 @@ t_operand t_scope_put::f_emit(t_emit& a_emit, bool a_tail, bool a_operand, bool
 			a_emit << e_instruction__FLOAT << v_variable.v_index << operand.v_float;
 			break;
 		case t_operand::e_tag__LITERAL:
-			switch (operand.v_value->f_tag()) {
+			switch (reinterpret_cast<uintptr_t>(operand.v_value)) {
 			case e_tag__NULL:
 				a_emit << e_instruction__NUL << v_variable.v_index;
 				break;
-			case e_tag__BOOLEAN:
-				a_emit << e_instruction__BOOLEAN << v_variable.v_index << operand.v_value->f_boolean();
+			case e_tag__TRUE:
+				a_emit << e_instruction__TRU << v_variable.v_index;
 				break;
 			default:
-				a_emit << e_instruction__INSTANCE << v_variable.v_index << *operand.v_value;
+				a_emit << e_instruction__INSTANCE << v_variable.v_index << operand.v_value;
 			}
 			break;
 		case t_operand::e_tag__VARIABLE:
@@ -802,15 +802,15 @@ t_operand t_super::f_emit(t_emit& a_emit, bool a_tail, bool a_operand, bool a_cl
 	return {};
 }
 
-t_operand t_null::f_emit(t_emit& a_emit, bool a_tail, bool a_operand, bool a_clear)
+t_operand t_boolean::f_emit(t_emit& a_emit, bool a_tail, bool a_operand, bool a_clear)
 {
-	if (a_operand) return nullptr;
+	if (a_operand) return reinterpret_cast<t_object*>(static_cast<uintptr_t>(v_value));
 	if (a_clear) return {};
 	if (a_tail) {
 		a_emit.f_emit_safe_point(this);
-		(a_emit << e_instruction__RETURN_NUL).f_push();
+		(a_emit << static_cast<t_instruction>(e_instruction__RETURN_NUL + v_value)).f_push();
 	} else {
-		a_emit.f_emit_null();
+		(a_emit << static_cast<t_instruction>(e_instruction__NUL + v_value) << a_emit.v_stack).f_push();
 	}
 	a_emit.f_at(this);
 	return {};
@@ -833,7 +833,7 @@ t_operand t_unary::f_emit(t_emit& a_emit, bool a_tail, bool a_operand, bool a_cl
 		case e_instruction__MINUS_T:
 			return t_literal<intptr_t>(v_at, -operand.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
 		case e_instruction__NOT_T:
-			return t_literal<bool>(v_at, false).f_emit(a_emit, a_tail, a_operand, a_clear);
+			return t_null(v_at).f_emit(a_emit, a_tail, a_operand, a_clear);
 		case e_instruction__COMPLEMENT_T:
 			return t_literal<intptr_t>(v_at, ~operand.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
 		default:
@@ -847,7 +847,7 @@ t_operand t_unary::f_emit(t_emit& a_emit, bool a_tail, bool a_operand, bool a_cl
 		case e_instruction__MINUS_T:
 			return t_literal<double>(v_at, -operand.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
 		case e_instruction__NOT_T:
-			return t_literal<bool>(v_at, false).f_emit(a_emit, a_tail, a_operand, a_clear);
+			return t_null(v_at).f_emit(a_emit, a_tail, a_operand, a_clear);
 		default:
 			f_throw(L"not supported."sv);
 		}
@@ -870,7 +870,7 @@ t_operand t_unary::f_emit(t_emit& a_emit, bool a_tail, bool a_operand, bool a_cl
 	if (!a_tail) a_emit << a_emit.v_stack;
 	switch (operand.v_tag) {
 	case t_operand::e_tag__LITERAL:
-		a_emit << *operand.v_value;
+		a_emit << operand.v_value;
 		break;
 	case t_operand::e_tag__VARIABLE:
 		a_emit << operand.v_index;
@@ -912,19 +912,19 @@ t_operand t_binary::f_emit(t_emit& a_emit, bool a_tail, bool a_operand, bool a_c
 			case e_instruction__RIGHT_SHIFT_TT:
 				return t_literal<intptr_t>(v_at, static_cast<uintptr_t>(left.v_integer) >> right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__LESS_TT:
-				return t_literal<bool>(v_at, left.v_integer < right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, left.v_integer < right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__LESS_EQUAL_TT:
-				return t_literal<bool>(v_at, left.v_integer <= right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, left.v_integer <= right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__GREATER_TT:
-				return t_literal<bool>(v_at, left.v_integer > right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, left.v_integer > right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__GREATER_EQUAL_TT:
-				return t_literal<bool>(v_at, left.v_integer >= right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, left.v_integer >= right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__EQUALS_TT:
 			case e_instruction__IDENTICAL_TT:
-				return t_literal<bool>(v_at, left.v_integer == right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, left.v_integer == right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__NOT_EQUALS_TT:
 			case e_instruction__NOT_IDENTICAL_TT:
-				return t_literal<bool>(v_at, left.v_integer != right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, left.v_integer != right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__AND_TT:
 				return t_literal<intptr_t>(v_at, left.v_integer & right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__XOR_TT:
@@ -946,21 +946,21 @@ t_operand t_binary::f_emit(t_emit& a_emit, bool a_tail, bool a_operand, bool a_c
 			case e_instruction__SUBTRACT_TT:
 				return t_literal<double>(v_at, left.v_integer - right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__LESS_TT:
-				return t_literal<bool>(v_at, left.v_integer < right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, left.v_integer < right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__LESS_EQUAL_TT:
-				return t_literal<bool>(v_at, left.v_integer <= right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, left.v_integer <= right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__GREATER_TT:
-				return t_literal<bool>(v_at, left.v_integer > right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, left.v_integer > right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__GREATER_EQUAL_TT:
-				return t_literal<bool>(v_at, left.v_integer >= right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, left.v_integer >= right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__EQUALS_TT:
-				return t_literal<bool>(v_at, left.v_integer == right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, left.v_integer == right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__NOT_EQUALS_TT:
-				return t_literal<bool>(v_at, left.v_integer != right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, left.v_integer != right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__IDENTICAL_TT:
-				return t_literal<bool>(v_at, false).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, false).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__NOT_IDENTICAL_TT:
-				return t_literal<bool>(v_at, true).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, true).f_emit(a_emit, a_tail, a_operand, a_clear);
 			default:
 				f_throw(L"not supported."sv);
 			}
@@ -978,21 +978,21 @@ t_operand t_binary::f_emit(t_emit& a_emit, bool a_tail, bool a_operand, bool a_c
 			case e_instruction__SUBTRACT_TT:
 				return t_literal<double>(v_at, left.v_float - right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__LESS_TT:
-				return t_literal<bool>(v_at, left.v_float < right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, left.v_float < right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__LESS_EQUAL_TT:
-				return t_literal<bool>(v_at, left.v_float <= right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, left.v_float <= right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__GREATER_TT:
-				return t_literal<bool>(v_at, left.v_float > right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, left.v_float > right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__GREATER_EQUAL_TT:
-				return t_literal<bool>(v_at, left.v_float >= right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, left.v_float >= right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__EQUALS_TT:
-				return t_literal<bool>(v_at, left.v_float == right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, left.v_float == right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__NOT_EQUALS_TT:
-				return t_literal<bool>(v_at, left.v_float != right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, left.v_float != right.v_integer).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__IDENTICAL_TT:
-				return t_literal<bool>(v_at, false).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, false).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__NOT_IDENTICAL_TT:
-				return t_literal<bool>(v_at, true).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, true).f_emit(a_emit, a_tail, a_operand, a_clear);
 			default:
 				f_throw(L"not supported."sv);
 			}
@@ -1008,19 +1008,19 @@ t_operand t_binary::f_emit(t_emit& a_emit, bool a_tail, bool a_operand, bool a_c
 			case e_instruction__SUBTRACT_TT:
 				return t_literal<double>(v_at, left.v_float - right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__LESS_TT:
-				return t_literal<bool>(v_at, left.v_float < right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, left.v_float < right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__LESS_EQUAL_TT:
-				return t_literal<bool>(v_at, left.v_float <= right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, left.v_float <= right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__GREATER_TT:
-				return t_literal<bool>(v_at, left.v_float > right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, left.v_float > right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__GREATER_EQUAL_TT:
-				return t_literal<bool>(v_at, left.v_float >= right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, left.v_float >= right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__EQUALS_TT:
 			case e_instruction__IDENTICAL_TT:
-				return t_literal<bool>(v_at, left.v_float == right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, left.v_float == right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
 			case e_instruction__NOT_EQUALS_TT:
 			case e_instruction__NOT_IDENTICAL_TT:
-				return t_literal<bool>(v_at, left.v_float != right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
+				return t_boolean(v_at, left.v_float != right.v_float).f_emit(a_emit, a_tail, a_operand, a_clear);
 			default:
 				f_throw(L"not supported."sv);
 			}
@@ -1071,7 +1071,7 @@ t_operand t_binary::f_emit(t_emit& a_emit, bool a_tail, bool a_operand, bool a_c
 		a_emit << left.v_float;
 		break;
 	case t_operand::e_tag__LITERAL:
-		a_emit << *left.v_value;
+		a_emit << left.v_value;
 		break;
 	case t_operand::e_tag__VARIABLE:
 		a_emit << left.v_index;
@@ -1085,7 +1085,7 @@ t_operand t_binary::f_emit(t_emit& a_emit, bool a_tail, bool a_operand, bool a_c
 		a_emit << right.v_float;
 		break;
 	case t_operand::e_tag__LITERAL:
-		a_emit << *right.v_value;
+		a_emit << right.v_value;
 		break;
 	case t_operand::e_tag__VARIABLE:
 		a_emit << right.v_index;
diff --git a/src/code.cc b/src/code.cc
index fb58a803..7bef267e 100644
--- a/src/code.cc
+++ b/src/code.cc
@@ -88,12 +88,12 @@ size_t t_code::f_loop(t_context* a_context, const void*** a_labels)
 			&&label__CLASS,
 			&&label__SUPER,
 			&&label__NUL,
-			&&label__BOOLEAN,
+			&&label__TRU,
 			&&label__INTEGER,
 			&&label__FLOAT,
 			&&label__INSTANCE,
 			&&label__RETURN_NUL,
-			&&label__RETURN_BOOLEAN,
+			&&label__RETURN_TRU,
 			&&label__RETURN_INTEGER,
 			&&label__RETURN_FLOAT,
 			&&label__RETURN_INSTANCE,
@@ -451,12 +451,11 @@ size_t t_code::f_loop(t_context* a_context)
 				stack[0] = nullptr;
 			}
 			XEMMAI__CODE__BREAK
-		XEMMAI__CODE__CASE(BOOLEAN)
+		XEMMAI__CODE__CASE(TRU)
 			{
 				auto stack = base + reinterpret_cast<size_t>(*++pc);
-				auto value = reinterpret_cast<intptr_t>(*++pc) != 0;
 				++pc;
-				stack[0] = value;
+				stack[0] = true;
 			}
 			XEMMAI__CODE__BREAK
 		XEMMAI__CODE__CASE(INTEGER)
@@ -485,7 +484,7 @@ size_t t_code::f_loop(t_context* a_context)
 		XEMMAI__CODE__CASE(INSTANCE)
 			{
 				auto stack = base + reinterpret_cast<size_t>(*++pc);
-				auto& value = *static_cast<const t_pvalue*>(*++pc);
+				auto value = static_cast<t_object*>(*++pc);
 				++pc;
 				stack[0] = value;
 			}
@@ -493,8 +492,8 @@ size_t t_code::f_loop(t_context* a_context)
 		XEMMAI__CODE__CASE(RETURN_NUL)
 			a_context->f_return(nullptr);
 			return -1;
-		XEMMAI__CODE__CASE(RETURN_BOOLEAN)
-			a_context->f_return(reinterpret_cast<intptr_t>(*++pc) != 0);
+		XEMMAI__CODE__CASE(RETURN_TRU)
+			a_context->f_return(true);
 			return -1;
 		XEMMAI__CODE__CASE(RETURN_INTEGER)
 			a_context->f_return(reinterpret_cast<intptr_t>(*++pc));
@@ -506,7 +505,7 @@ size_t t_code::f_loop(t_context* a_context)
 			}
 			return -1;
 		XEMMAI__CODE__CASE(RETURN_INSTANCE)
-			a_context->f_return(*static_cast<const t_pvalue*>(*++pc));
+			a_context->f_return(static_cast<t_object*>(*++pc));
 			return -1;
 		XEMMAI__CODE__CASE(RETURN_V)
 			a_context->f_return(base[reinterpret_cast<size_t>(*++pc)]);
@@ -579,7 +578,7 @@ size_t t_code::f_loop(t_context* a_context)
 				auto& a0 = stack[1];
 #define XEMMAI__CODE__PREPARE()
 #define XEMMAI__CODE__FETCH_L()\
-				auto& a0 = *static_cast<const t_pvalue*>(*++pc);
+				t_pvalue a0 = static_cast<t_object*>(*++pc);
 #define XEMMAI__CODE__PREPARE_L()
 #define XEMMAI__CODE__FETCH_V()\
 				auto& a0 = base[reinterpret_cast<size_t>(*++pc)];
@@ -589,7 +588,7 @@ size_t t_code::f_loop(t_context* a_context)
 #define XEMMAI__CODE__PREPARE_A1()\
 						stack[2] = a1;
 #define XEMMAI__CODE__FETCH_LI()\
-				auto& a0 = *static_cast<const t_pvalue*>(*++pc);\
+				t_pvalue a0 = static_cast<t_object*>(*++pc);\
 				auto a1 = reinterpret_cast<intptr_t>(*++pc);
 #define XEMMAI__CODE__PREPARE_LI() XEMMAI__CODE__PREPARE_A1()
 #define XEMMAI__CODE__FETCH_VI()\
@@ -601,7 +600,7 @@ size_t t_code::f_loop(t_context* a_context)
 				auto a1 = reinterpret_cast<intptr_t>(*++pc);
 #define XEMMAI__CODE__PREPARE_TI() XEMMAI__CODE__PREPARE_A1()
 #define XEMMAI__CODE__FETCH_LF()\
-				auto& a0 = *static_cast<const t_pvalue*>(*++pc);\
+				t_pvalue a0 = static_cast<t_object*>(*++pc);\
 				XEMMAI__CODE__FLOAT(a1, v1)
 #define XEMMAI__CODE__PREPARE_LF() XEMMAI__CODE__PREPARE_A1()
 #define XEMMAI__CODE__FETCH_VF()\
@@ -614,21 +613,21 @@ size_t t_code::f_loop(t_context* a_context)
 #define XEMMAI__CODE__PREPARE_TF() XEMMAI__CODE__PREPARE_A1()
 #define XEMMAI__CODE__FETCH_IL()\
 				auto a0 = reinterpret_cast<intptr_t>(*++pc);\
-				auto& a1 = *static_cast<const t_pvalue*>(*++pc);
+				t_pvalue a1 = static_cast<t_object*>(*++pc);
 #define XEMMAI__CODE__FETCH_FL()\
 				XEMMAI__CODE__FLOAT(a0, v0)\
-				auto& a1 = *static_cast<const t_pvalue*>(*++pc);
+				t_pvalue a1 = static_cast<t_object*>(*++pc);
 #define XEMMAI__CODE__FETCH_LL()\
-				auto& a0 = *static_cast<const t_pvalue*>(*++pc);\
-				auto& a1 = *static_cast<const t_pvalue*>(*++pc);
+				t_pvalue a0 = static_cast<t_object*>(*++pc);\
+				t_pvalue a1 = static_cast<t_object*>(*++pc);
 #define XEMMAI__CODE__PREPARE_LL() XEMMAI__CODE__PREPARE_A1()
 #define XEMMAI__CODE__FETCH_VL()\
 				auto& a0 = base[reinterpret_cast<size_t>(*++pc)];\
-				auto& a1 = *static_cast<const t_pvalue*>(*++pc);
+				t_pvalue a1 = static_cast<t_object*>(*++pc);
 #define XEMMAI__CODE__PREPARE_VL() XEMMAI__CODE__PREPARE_A1()
 #define XEMMAI__CODE__FETCH_TL()\
 				auto& a0 = stack[1];\
-				auto& a1 = *static_cast<const t_pvalue*>(*++pc);
+				t_pvalue a1 = static_cast<t_object*>(*++pc);
 #define XEMMAI__CODE__PREPARE_TL() XEMMAI__CODE__PREPARE_A1()
 #define XEMMAI__CODE__FETCH_IV()\
 				auto a0 = reinterpret_cast<intptr_t>(*++pc);\
@@ -637,7 +636,7 @@ size_t t_code::f_loop(t_context* a_context)
 				XEMMAI__CODE__FLOAT(a0, v0)\
 				auto& a1 = base[reinterpret_cast<size_t>(*++pc)];
 #define XEMMAI__CODE__FETCH_LV()\
-				auto& a0 = *static_cast<const t_pvalue*>(*++pc);\
+				t_pvalue a0 = static_cast<t_object*>(*++pc);\
 				auto& a1 = base[reinterpret_cast<size_t>(*++pc)];
 #define XEMMAI__CODE__PREPARE_LV() XEMMAI__CODE__PREPARE_A1()
 #define XEMMAI__CODE__FETCH_VV()\
@@ -655,7 +654,7 @@ size_t t_code::f_loop(t_context* a_context)
 				XEMMAI__CODE__FLOAT(a0, v0)\
 				auto& a1 = stack[1];
 #define XEMMAI__CODE__FETCH_LT()\
-				auto& a0 = *static_cast<const t_pvalue*>(*++pc);\
+				t_pvalue a0 = static_cast<t_object*>(*++pc);\
 				auto& a1 = stack[1];
 #define XEMMAI__CODE__PREPARE_LT() XEMMAI__CODE__PREPARE_A1()
 #define XEMMAI__CODE__FETCH_VT()\
diff --git a/src/code_operator.h b/src/code_operator.h
index 597909dc..2f1c9eb7 100644
--- a/src/code_operator.h
+++ b/src/code_operator.h
@@ -13,12 +13,6 @@
 				} else {\
 					XEMMAI__CODE__PRIMITIVE_CALL(a_operator(false))\
 				}
-#define XEMMAI__CODE__BOOLEAN_OR_THROW(a_operator)\
-					if (a1.f_tag() == e_tag__BOOLEAN) {\
-						XEMMAI__CODE__PRIMITIVE_CALL(static_cast<bool>(a0.v_boolean a_operator a1.v_boolean))\
-					} else {\
-						goto label__THROW_NOT_SUPPORTED;\
-					}
 #define XEMMAI__CODE__OTHERS_OBJECT(a_name, a_method)\
 		XEMMAI__CODE__CASE_BEGIN(a_name)\
 				XEMMAI__CODE__OBJECT_OR_THROW(a_method)\
@@ -32,7 +26,7 @@
 		XEMMAI__CODE__CASE_BEGIN(a_name)\
 				switch (a0.f_tag()) {\
 				case e_tag__NULL:\
-				case e_tag__BOOLEAN:\
+				case e_tag__TRUE:\
 					goto label__THROW_NOT_SUPPORTED;\
 				case e_tag__INTEGER:\
 					XEMMAI__CODE__PRIMITIVE_CALL(a_operator(a0.v_integer))\
@@ -47,7 +41,7 @@
 		XEMMAI__CODE__UNARY_ARITHMETIC(PLUS, , f_plus)
 		XEMMAI__CODE__UNARY_ARITHMETIC(MINUS, -, f_minus)
 		XEMMAI__CODE__CASE_BEGIN(NOT)
-				XEMMAI__CODE__PRIMITIVE_CALL(!f_as<bool>(a0))
+				XEMMAI__CODE__PRIMITIVE_CALL(!a0)
 		XEMMAI__CODE__CASE_END
 		XEMMAI__CODE__CASE_BEGIN(COMPLEMENT)
 				if (a0.f_tag() == e_tag__INTEGER) {
@@ -101,9 +95,14 @@
 #define XEMMAI__CODE__BINARY_EQUALITY_PRIMITIVE(a_operator)
 #define XEMMAI__CODE__BINARY_BITWISE(a_name, a_operator, a_method)\
 		XEMMAI__CODE__CASE_BEGIN(a_name)\
-				if (a0.f_tag() == e_tag__BOOLEAN) {\
-					XEMMAI__CODE__BOOLEAN_OR_THROW(a_operator)\
-				} else XEMMAI__CODE__OBJECT_OR_THROW(a_method)\
+				switch (a0.f_tag()) {\
+				case e_tag__NULL:\
+				case e_tag__TRUE:\
+					XEMMAI__CODE__PRIMITIVE_CALL(static_cast<bool>(f_as<bool>(a0) a_operator f_as<bool>(a1)))\
+					break;\
+				default:\
+					XEMMAI__CODE__OBJECT_CALL(a_method)\
+				}\
 		XEMMAI__CODE__CASE_END
 #else
 #ifdef XEMMAI__CODE__BINARY_XL
@@ -145,7 +144,7 @@
 		XEMMAI__CODE__CASE_BEGIN(a_name)\
 				switch (a0.f_tag()) {\
 				case e_tag__NULL:\
-				case e_tag__BOOLEAN:\
+				case e_tag__TRUE:\
 					goto label__THROW_NOT_SUPPORTED;\
 				case e_tag__INTEGER:\
 					XEMMAI__CODE__BINARY_ARITHMETIC_INTEGER(a_operator)\
@@ -178,14 +177,14 @@
 #define XEMMAI__CODE__BINARY_BITWISE(a_name, a_operator, a_method)\
 		XEMMAI__CODE__CASE_BEGIN(a_name)\
 				switch (a0.f_tag()) {\
-				case e_tag__BOOLEAN:\
-					XEMMAI__CODE__BOOLEAN_OR_THROW(a_operator)\
+				case e_tag__NULL:\
+				case e_tag__TRUE:\
+					XEMMAI__CODE__PRIMITIVE_CALL(static_cast<bool>(f_as<bool>(a0) a_operator f_as<bool>(a1)))\
 					break;\
 				case e_tag__INTEGER:\
 					XEMMAI__CODE__BINARY_INTEGER(a_operator, )\
 					XEMMAI__CODE__BINARY_DERIVED_OR_THROW(a_operator, intptr_t, , .v_integer)\
 					break;\
-				case e_tag__NULL:\
 				case e_tag__FLOAT:\
 					goto label__THROW_NOT_SUPPORTED;\
 				default:\
@@ -197,10 +196,8 @@
 		XEMMAI__CODE__CASE_BEGIN(a_name)\
 				switch (a0.f_tag()) {\
 				case e_tag__NULL:\
-					XEMMAI__CODE__PRIMITIVE_CALL(a_operator(a1.f_tag() == e_tag__NULL))\
-					break;\
-				case e_tag__BOOLEAN:\
-					XEMMAI__CODE__PRIMITIVE_CALL(a_operator(a1.f_tag() == e_tag__BOOLEAN && a0.v_boolean == a1.v_boolean))\
+				case e_tag__TRUE:\
+					XEMMAI__CODE__PRIMITIVE_CALL(a_operator(a0.f_tag() == a1.f_tag()))\
 					break;\
 				XEMMAI__CODE__BINARY_EQUALITY_PRIMITIVE(a_operator)\
 				default:\
diff --git a/src/global.cc b/src/global.cc
index 919a7906..3489e389 100644
--- a/src/global.cc
+++ b/src/global.cc
@@ -23,7 +23,6 @@ void t_global::f_scan(t_scan a_scan)
 	a_scan(v_type_advanced_lambda_shared);
 	a_scan(v_type_method);
 	a_scan(v_type_throwable);
-	a_scan(v_type_null);
 	a_scan(v_type_boolean);
 	a_scan(v_type_integer);
 	a_scan(v_type_float);
@@ -129,8 +128,6 @@ std::vector<std::pair<t_root, t_rvalue>> t_global::f_define()
 	v_type_method->v_builtin = true;
 	t_type_of<t_throwable>::f_define();
 	v_type_throwable->v_builtin = true;
-	t_type_of<std::nullptr_t>::f_define();
-	v_type_null->v_builtin = true;
 	t_type_of<bool>::f_define();
 	v_type_boolean->v_builtin = true;
 	t_type_of<intptr_t>::f_define();
@@ -164,7 +161,7 @@ std::vector<std::pair<t_root, t_rvalue>> t_global::f_define()
 		(L"Lambda"sv, static_cast<t_object*>(v_type_lambda))
 		(L"Method"sv, static_cast<t_object*>(v_type_method))
 		(L"Throwable"sv, static_cast<t_object*>(v_type_throwable))
-		(L"Null"sv, static_cast<t_object*>(v_type_null))
+		(L"Null"sv, static_cast<t_object*>(v_type_boolean))
 		(L"Boolean"sv, static_cast<t_object*>(v_type_boolean))
 		(L"Integer"sv, static_cast<t_object*>(v_type_integer))
 		(L"Float"sv, static_cast<t_object*>(v_type_float))
diff --git a/src/main.cc b/src/main.cc
index 4cbc651b..cf80c925 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -189,8 +189,8 @@ class t_debugger : public xemmai::t_debugger
 		case e_tag__NULL:
 			std::fputs("null", v_out);
 			break;
-		case e_tag__BOOLEAN:
-			std::fputs(f_as<bool>(a_value) ? "true" : "false", v_out);
+		case e_tag__TRUE:
+			std::fputs("true", v_out);
 			break;
 		case e_tag__INTEGER:
 			std::fprintf(v_out, "%" PRIdPTR, f_as<intptr_t>(a_value));
diff --git a/src/null.cc b/src/null.cc
deleted file mode 100644
index 178af74d..00000000
--- a/src/null.cc
+++ /dev/null
@@ -1,13 +0,0 @@
-#include <xemmai/convert.h>
-
-namespace xemmai
-{
-
-void t_type_of<std::nullptr_t>::f_define()
-{
-	t_define{f_global()}
-		(f_global()->f_symbol_string(), t_member<t_object*(*)(const t_pvalue&), f__string>())
-	.f_derive<std::nullptr_t, t_object>();
-}
-
-}
diff --git a/src/parser.cc b/src/parser.cc
index 8b8c70f6..e9448315 100644
--- a/src/parser.cc
+++ b/src/parser.cc
@@ -36,7 +36,7 @@ std::unique_ptr<ast::t_node> t_parser::f_target(bool a_assignable)
 			switch (v_lexer.f_token()) {
 			case t_lexer::e_token__SYMBOL:
 				{
-					t_object* symbol = f_symbol();
+					auto symbol = f_symbol();
 					v_lexer.f_next();
 					if (v_lexer.f_token() == t_lexer::e_token__EQUAL) {
 						if (!a_assignable) f_throw(L"can not assign to expression."sv);
@@ -58,7 +58,7 @@ std::unique_ptr<ast::t_node> t_parser::f_target(bool a_assignable)
 					v_lexer.f_next();
 					if (!v_lexer.f_newline() && v_lexer.f_token() == t_lexer::e_token__SYMBOL) {
 						t_at at = v_lexer.f_at();
-						t_object* key = f_symbol();
+						auto key = f_symbol();
 						v_lexer.f_next();
 						if (v_lexer.f_token() == t_lexer::e_token__EQUAL) {
 							if (!a_assignable) f_throw(L"can not assign to expression."sv);
@@ -78,15 +78,15 @@ std::unique_ptr<ast::t_node> t_parser::f_target(bool a_assignable)
 		switch (v_lexer.f_token()) {
 		case t_lexer::e_token__SYMBOL:
 			{
-				auto& symbol = f_symbol();
+				auto symbol = f_symbol();
 				v_lexer.f_next();
-				return std::make_unique<ast::t_literal<t_svalue&>>(at, symbol);
+				return std::make_unique<ast::t_literal<t_object*>>(at, symbol);
 			}
 		case t_lexer::e_token__LEFT_PARENTHESIS:
 			{
 				size_t indent = v_lexer.f_indent();
 				v_lexer.f_next();
-				auto call = std::make_unique<ast::t_call>(at, std::make_unique<ast::t_literal<t_svalue&>>(at, v_module.f_slot(t_object::f_of(f_global()->f_type<t_tuple>()))));
+				auto call = std::make_unique<ast::t_call>(at, std::make_unique<ast::t_literal<t_object*>>(at, v_module.f_slot(t_object::f_of(f_global()->f_type<t_tuple>()))));
 				if ((!v_lexer.f_newline() || v_lexer.f_indent() > indent) && v_lexer.f_token() != t_lexer::e_token__RIGHT_PARENTHESIS) call->v_expand = f_expressions(indent, call->v_arguments);
 				if ((!v_lexer.f_newline() || v_lexer.f_indent() >= indent) && v_lexer.f_token() == t_lexer::e_token__RIGHT_PARENTHESIS) v_lexer.f_next();
 				return call;
@@ -193,7 +193,7 @@ std::unique_ptr<ast::t_node> t_parser::f_target(bool a_assignable)
 		{
 			size_t indent = v_lexer.f_indent();
 			v_lexer.f_next();
-			auto call = std::make_unique<ast::t_call>(at, std::make_unique<ast::t_literal<t_svalue&>>(at, v_module.f_slot(t_object::f_of(f_global()->f_type<t_list>()))));
+			auto call = std::make_unique<ast::t_call>(at, std::make_unique<ast::t_literal<t_object*>>(at, v_module.f_slot(t_object::f_of(f_global()->f_type<t_list>()))));
 			if ((!v_lexer.f_newline() || v_lexer.f_indent() > indent) && v_lexer.f_token() != t_lexer::e_token__RIGHT_BRACKET) call->v_expand = f_expressions(indent, call->v_arguments);
 			if ((!v_lexer.f_newline() || v_lexer.f_indent() >= indent) && v_lexer.f_token() == t_lexer::e_token__RIGHT_BRACKET) v_lexer.f_next();
 			return call;
@@ -202,7 +202,7 @@ std::unique_ptr<ast::t_node> t_parser::f_target(bool a_assignable)
 		{
 			size_t indent = v_lexer.f_indent();
 			v_lexer.f_next();
-			auto call = std::make_unique<ast::t_call>(at, std::make_unique<ast::t_literal<t_svalue&>>(at, v_module.f_slot(t_object::f_of(f_global()->f_type<t_map>()))));
+			auto call = std::make_unique<ast::t_call>(at, std::make_unique<ast::t_literal<t_object*>>(at, v_module.f_slot(t_object::f_of(f_global()->f_type<t_map>()))));
 			if ((!v_lexer.f_newline() || v_lexer.f_indent() > indent) && v_lexer.f_token() != t_lexer::e_token__RIGHT_BRACE)
 				while (true) {
 					call->v_arguments.push_back(f_expression());
@@ -220,14 +220,12 @@ std::unique_ptr<ast::t_node> t_parser::f_target(bool a_assignable)
 			return call;
 		}
 	case t_lexer::e_token__NULL:
+	case t_lexer::e_token__FALSE:
 		v_lexer.f_next();
 		return std::make_unique<ast::t_null>(at);
 	case t_lexer::e_token__TRUE:
 		v_lexer.f_next();
-		return std::make_unique<ast::t_literal<bool>>(at, true);
-	case t_lexer::e_token__FALSE:
-		v_lexer.f_next();
-		return std::make_unique<ast::t_literal<bool>>(at, false);
+		return std::make_unique<ast::t_boolean>(at, true);
 	case t_lexer::e_token__INTEGER:
 		{
 			auto value = v_lexer.f_integer();
@@ -244,7 +242,7 @@ std::unique_ptr<ast::t_node> t_parser::f_target(bool a_assignable)
 		{
 			auto value = v_lexer.f_string();
 			v_lexer.f_next();
-			return std::make_unique<ast::t_literal<t_svalue&>>(at, v_module.f_slot(value));
+			return std::make_unique<ast::t_literal<t_object*>>(at, v_module.f_slot(value));
 		}
 	case t_lexer::e_token__BREAK:
 		{
@@ -314,7 +312,7 @@ std::unique_ptr<ast::t_node> t_parser::f_action(size_t a_indent, std::unique_ptr
 					}
 				case t_lexer::e_token__SYMBOL:
 					{
-						t_object* key = f_symbol();
+						auto key = f_symbol();
 						v_lexer.f_next();
 						if (v_lexer.f_token() == t_lexer::e_token__EQUAL) {
 							if (!a_assignable) f_throw(L"can not assign to expression."sv);
@@ -346,7 +344,7 @@ std::unique_ptr<ast::t_node> t_parser::f_action(size_t a_indent, std::unique_ptr
 						}
 					case t_lexer::e_token__SYMBOL:
 						{
-							t_object* key = f_symbol();
+							auto key = f_symbol();
 							v_lexer.f_next();
 							a_target.reset(new ast::t_object_has(at, std::move(a_target), key));
 							continue;
@@ -709,7 +707,7 @@ std::unique_ptr<ast::t_node> t_parser::f_expression()
 					v_lexer.f_next();
 					auto expression = f_expression();
 					if (v_lexer.f_token() != t_lexer::e_token__SYMBOL) f_throw(L"expecting symbol."sv);
-					t_object* symbol = f_symbol();
+					auto symbol = f_symbol();
 					v_lexer.f_next();
 					auto c = std::make_unique<ast::t_try::t_catch>(std::move(expression), f_variable(v_scope, symbol));
 					f_block_or_expression(indent, c->v_block);
diff --git a/test/operators.xm b/test/operators.xm
index 13084713..42fac66c 100644
--- a/test/operators.xm
+++ b/test/operators.xm
@@ -30,7 +30,7 @@ assert(a["x"] == "a[x]"
 assert((a["x"] = "y") == "a[x] = y"
 assert(+a == "+a"
 assert(-a == "-a"
-assert(!a === false
+assert(!a === null
 assert(~a == "~a"
 assert(a * "x" == "a * x"
 assert(a / "x" == "a / x"
diff --git a/test/primitives.xm b/test/primitives.xm
index 7f9a745a..93264e91 100644
--- a/test/primitives.xm
+++ b/test/primitives.xm
@@ -2,6 +2,8 @@ system = Module("system"
 print = system.out.write_line
 assert = @(x) x || throw Throwable("Assertion failed."
 
+assert(false === null
+
 print("!false = " + !false
 assert(!false === true
 print("!true = " + !true