diff --git a/README.md b/README.md
index 5ba8b10..9516c06 100644
--- a/README.md
+++ b/README.md
@@ -10,15 +10,40 @@ $ ./build.sh
 
 # example
 
-![lispoo.png](./lispoo.png)
+> lambda.lisp
+
+```lisp
+(progn
+  (define abc (lambda (a b c) (+ a (+ b c))))
+  (set! x (abc 1 2 3))
+  (message x)
+  (progn (+ 1.2 3.9) (define plus (lambda (a b) (+ a b))) (message (plus 9 9)))
+  )
+```
 
 ```sh
 $ ./lispoo example/lambda.lisp
-(6)(18)
+8
+18
+```
 
-$ ./lispoo example/prog.lisp
-(3)(2)(1)(2)(1)
+> quote.lisp
+
+```lisp
+(progn
+  (define test (lambda (x) x))
+  (if (test (quote (+ 1 -1)))
+      (message (quote true))
+    (message (quote false))
+    )
+  (message (quote (+ 1 2)))
+  )
+```
 
+```sh
 $ ./lispoo example/quote.lisp
-("false")((+ 1 2))
-```
\ No newline at end of file
+false
+(+ 1 2)
+```
+
+[More Examples](./example)
diff --git a/core.h b/core.h
index 3c942cc..1f9f2ff 100644
--- a/core.h
+++ b/core.h
@@ -4,9 +4,8 @@
 
 namespace lispoo {
 
-inline std::shared_ptr<Expr> sum(const std::shared_ptr<List>& args) {
-  assert_len(args, 2);
-  auto a = args->value()[0], b = args->value()[1];
+inline std::shared_ptr<Expr> sum(const std::shared_ptr<Expr>& a,
+                                 const std::shared_ptr<Expr>& b) {
   if (a->type() == Type::Float
       && b->type() == Type::Float) {
     return std::make_shared<Float>(get_value<Float>(a) + get_value<Float>(b));
@@ -64,4 +63,105 @@ inline std::shared_ptr<Expr> message(const std::shared_ptr<Expr>& expr) {
   return nil;
 }
 
+inline void init() {
+  // syntax
+  putenv("quote",
+         [](auto expr, auto env) {
+           assert_len(expr, 2);
+           auto value = get_value<List>(expr);
+           return value[1];
+         });
+  putenv("define",
+         [](auto expr, auto env) {
+           assert_len(expr, 3);
+           auto value = get_value<List>(expr);
+           assert_type<Type::Symbol>(value[1]);
+           auto symbol = get_value<Symbol>(value[1]);
+           if (!is_nil(env->get(symbol))) {
+             oops("symbol defined: " + symbol);
+           }
+           env->put(symbol, eval(value[2], env));
+           return nil;
+         });
+  putenv("set!",
+         [](auto expr, auto env) {
+           assert_len(expr, 3);
+           auto value = get_value<List>(expr);
+           assert_type<Type::Symbol>(value[1]);
+           auto symbol = get_value<Symbol>(value[1]);
+           env->put(symbol, eval(value[2], env));
+           return nil;
+         });
+  putenv("progn",
+         [](auto expr, auto env) {
+           auto val = nil;
+           auto value = get_value<List>(expr);
+           for (auto i = 1; i < value.size(); ++i) {
+             val = eval(value[i], env);
+           }
+           return val;
+         });
+  putenv("if",
+         [](auto expr, auto env) {
+           // (if (cond) (then body) (else body))
+           assert_len(expr, 4);
+           auto value = get_value<List>(expr);
+           if (is_true(eval(value[1], env))) {
+             return eval(value[2], env);
+           } else {
+             return eval(value[3], env);
+           }
+         });
+  putenv("while",
+         [](auto expr, auto env) {
+           // (while (cond) (loop body))
+           assert_len(expr, 3);
+           auto value = get_value<List>(expr);
+           while (is_true(eval(value[1], env))) {
+             eval(value[2], env);
+           }
+           return nil;
+         });
+  putenv("lambda",
+         [](auto expr, auto env) {
+           // (lambda (args) (body))
+           assert_len(expr, 3);
+           auto lambda =
+             [expr, parent = env](auto args, auto) {
+               auto value = get_value<List>(expr);
+               auto symbols = get_value<List>(value[1]);
+               // arguments bind
+               auto args_value = get_value<List>(args);
+               if (symbols.size() != args_value.size() - 1) {
+                 oops("arguments error");
+               }
+               auto env = std::make_shared<Env>(parent);
+               for (auto i = 0; i < symbols.size(); ++i) {
+                 auto symbol = get_value<Symbol>(symbols[i]);
+                 env->put(symbol, eval(args_value[i + 1], parent));
+               }
+               // eval body
+               return eval(value[2], env);
+             };
+           return std::make_shared<Callable>(std::move(lambda));
+         });
+
+  // normal builtin function
+  putenv("+",
+         [](auto expr, auto env) {
+           assert_len(expr, 3);
+           auto value = get_value<List>(expr);
+           return sum(eval(value[1], env), eval(value[2], env));
+         });
+  putenv("message",
+         [](auto expr, auto env) {
+           auto value = get_value<List>(expr);
+           for (auto i = 1; i < value.size(); ++i) {
+             message(eval(value[i], env));
+             std::cout << std::endl;
+           }
+           return nil;
+         });
+}
+
 } // namespace lispoo
diff --git a/example/lambda.lisp b/example/lambda.lisp
index 30835d9..b898221 100644
--- a/example/lambda.lisp
+++ b/example/lambda.lisp
@@ -1,6 +1,6 @@
-(prog
- (def abc (lambda (a b c) (+ a (+ b c))))
- (set! x (abc 1 2 3))
- (message x)
- (prog (+ 1.2 3.9) (def plus (lambda (a b) (+ a b))) (message (plus 9 9)))
- )
+(progn
+  (define abc (lambda (a b c) (+ a (+ b c))))
+  (set! x (abc 1 2 3))
+  (message x)
+  (progn (+ 1.2 3.9) (define plus (lambda (a b) (+ a b))) (message (plus 9 9)))
+  )
diff --git a/example/macro.lisp b/example/macro.lisp
index 2cefa80..98552ce 100644
--- a/example/macro.lisp
+++ b/example/macro.lisp
@@ -1,5 +1,5 @@
-(prog
- (message (quote (name args)))
- (def echo message)
- (echo 1)
- )
+(progn
+  (message (quote (name args)))
+  (define echo message)
+  (echo 1)
+  )
diff --git a/example/prog.lisp b/example/prog.lisp
index 848fd58..91ef6e2 100644
--- a/example/prog.lisp
+++ b/example/prog.lisp
@@ -1,6 +1,7 @@
-(prog
- (set! i 3)
- (while i (prog (message i) (set! i (+ i -1))))
- (prog (set! x 0) (message (if x 1 2)))
- (prog (set! x 1) (message x))
- )
+(progn
+  (set! i 3)
+  (while i (progn (message i) (set! i (+ i -1))))
+  (progn (set! x 0) (message (if x 1 2)))
+  (progn (set! x 1) (message x))
+  (message (progn (+ 1 1) (+ 2 2)))
+  )
diff --git a/example/quote.lisp b/example/quote.lisp
index 96a6700..982f723 100644
--- a/example/quote.lisp
+++ b/example/quote.lisp
@@ -1,8 +1,8 @@
-(prog
- (def test (lambda (x) x))
- (if (test (quote (+ 1 -1)))
-     (message (quote true))
-   (message (quote false))
-   )
- (message (quote (+ 1 2)))
- )
+(progn
+  (define test (lambda (x) x))
+  (if (test (quote (+ 1 -1)))
+      (message (quote true))
+    (message (quote false))
+    )
+  (message (quote (+ 1 2)))
+  )
diff --git a/example/sum.lisp b/example/sum.lisp
index 99168c4..8b482b5 100644
--- a/example/sum.lisp
+++ b/example/sum.lisp
@@ -1,6 +1,6 @@
-(prog
- (message (+
-           (+ 2 1.1)
-           1))
- (message (+ 1 2) (+ 1.1 1.1) (+ 2 1.1) (+ 1.9 -1))
- )
+(progn
+  (message (+
+            (+ 2 1.1)
+            1))
+  (message (+ 1 2) (+ 1.1 1.1) (+ 2 1.1) (+ 1.9 -1))
+  )
diff --git a/lispoo.cpp b/lispoo.cpp
index 87030af..05ddcae 100644
--- a/lispoo.cpp
+++ b/lispoo.cpp
@@ -13,31 +13,12 @@ int main(int argc, char* argv[]) {
     lispoo::oops("can't open: " + std::string(argv[1]));
   }
   ss << ifs.rdbuf();
+
+  lispoo::init();
+  unsigned long cursor = 0;
   std::vector<std::string> tokens;
   lispoo::tokenize(ss.str(), tokens);
-  unsigned long cursor = 0;
   auto expr = lispoo::parse(tokens, cursor);
-
-  lispoo::putenv("+", [](auto args) {
-    return lispoo::sum(args);
-  });
-  lispoo::putenv("car", [](auto args) {
-    return args->value()[0];
-  });
-  lispoo::putenv("cdr", [](auto args) {
-    auto value = args->value();
-    auto cdr = std::make_shared<lispoo::List>();
-    cdr->value().assign(value.begin() + 1, value.end());
-    return cdr;
-  });
-  lispoo::putenv("message", [](auto args) {
-    auto value = lispoo::get_value<lispoo::List>(args);
-    for (auto& v : value) {
-      lispoo::message(v);
-      std::cout << std::endl;
-    }
-    return lispoo::nil;
-  });
   lispoo::eval(expr, lispoo::global);
   return 0;
 }
diff --git a/lispoo.h b/lispoo.h
index ae44a3f..d7334fb 100644
--- a/lispoo.h
+++ b/lispoo.h
@@ -77,9 +77,11 @@ private:
   std::vector<std::shared_ptr<Expr>> value_;
 };
 
+class Env;
 class Callable: public Expr {
 public:
-  using Fn = std::function<std::shared_ptr<Expr>(const std::shared_ptr<List>&)>;
+  using Fn = std::function<std::shared_ptr<Expr>(const std::shared_ptr<Expr>&,
+                                                 const std::shared_ptr<Env>& env)>;
 
   explicit Callable(Fn&& lambda) : lambda_(lambda) {}
   Type type() override { return Type::Callable; }
@@ -248,70 +250,6 @@ inline std::shared_ptr<Expr> eval(const std::shared_ptr<Expr>& expr, const std::
   auto value = get_value<List>(expr);
   assert_type<Type::Symbol>(value[0]);
   auto name = get_value<Symbol>(value[0]);
-  if (name == "quote") {
-    assert_len(expr, 2);
-    return value[1];
-  }
-  if (name == "def") {
-    assert_len(expr, 3);
-    assert_type<Type::Symbol>(value[1]);
-    auto symbol = get_value<Symbol>(value[1]);
-    if (!is_nil(env->get(symbol))) {
-      oops("symbol defined: " + symbol);
-    }
-    env->put(symbol, eval(value[2], env));
-    return nil;
-  }
-  if (name == "set!") {
-    assert_len(expr, 3);
-    assert_type<Type::Symbol>(value[1]);
-    auto symbol = get_value<Symbol>(value[1]);
-    env->put(symbol, eval(value[2], env));
-    return nil;
-  }
-  if (name == "prog") {
-    for (auto i = 1; i < value.size(); ++i) {
-      eval(value[i], env);
-    }
-    return nil;
-  }
-  if (name == "if") {
-    // (if (cond) (then body) (else body))
-    assert_len(expr, 4);
-    if (is_true(eval(value[1], env))) {
-      return eval(value[2], env);
-    } else {
-      return eval(value[3], env);
-    }
-  }
-  if (name == "while") {
-    // (while (cond) (loop body))
-    assert_len(expr, 3);
-    while (is_true(eval(value[1], env))) {
-      eval(value[2], env);
-    }
-    return nil;
-  }
-  if (name == "lambda") {
-    // (lambda (args) (body))
-    assert_len(expr, 3);
-    auto lambda = [expr, parent = env](const std::shared_ptr<List>& args) {
-      auto value = get_value<List>(expr);
-      auto symbols = get_value<List>(value[1]);
-      // arguments bind
-      if (symbols.size() != args->value().size()) {
-        oops("arguments error");
-      }
-      auto env = std::make_shared<Env>(parent);
-      for (auto i = 0; i < symbols.size(); ++i) {
-        auto symbol = get_value<Symbol>(symbols[i]);
-        env->put(symbol, args->value()[i]);
-      }
-      // eval body
-      return eval(value[2], env);
-    };
-    return std::make_shared<Callable>(std::move(lambda));
-  }
   // function/lambda call
   // (symbol arg1 arg2 arg3 ... )
   auto callable = env->get(name);
@@ -321,11 +259,7 @@ inline std::shared_ptr<Expr> eval(const std::shared_ptr<Expr>& expr, const std::
   if (!is_type<Type::Callable>(callable)) {
     oops("can't call symbol: " + name);
   }
-  auto args = std::make_shared<List>();
-  for (auto i = 1; i < value.size(); ++i) {
-    args->append(eval(value[i], env));
-  }
-  return get_value<Callable>(callable)(args);
+  return get_value<Callable>(callable)(expr, env);
 }
 
 } // namespace lispoo
diff --git a/lispoo.png b/lispoo.png
deleted file mode 100644
index 255c2aa..0000000
Binary files a/lispoo.png and /dev/null differ