diff --git a/src/expand.clj b/src/expand.clj
index 37cc8d4..8433847 100644
--- a/src/expand.clj
+++ b/src/expand.clj
@@ -51,10 +51,10 @@
 
 (s/def ::identifier
   (s/and ::syntax
-         #(symbol? (scm/stx-datum %))))
+         #(symbol? (scm/syntax-e %))))
 
 (s/fdef expand
-  :args (s/cat :syntax ::syntax
+  :args (s/cat :stx ::syntax
                :env ::environment
                :store ::store)
   :ret ::syntax)
@@ -81,8 +81,8 @@
     (second (apply max-key first xs))))
 
 (defn lookup [ident env store]
-  (let [sym (scm/stx-datum ident)
-        scopes (scm/stx-context ident)
+  (let [sym (scm/syntax-e ident)
+        scopes (scm/syntax-context ident)
         ss (store-scopes store sym)]
     (let [xs (nearest scopes ss)
           r (compare (count xs) 1)]
@@ -93,4 +93,6 @@
                 (throw (ex-info "unreachable" {})))
             (pos? r) (throw (ex-info "ambiguous sym" {:sym sym}))))))
 
-(defn expand [stx env store-atom])
+(defn expand [stx env store-atom]
+  (match (scm/syntax-e stx)
+    (x :guard scm/constant?) x))
diff --git a/src/scm.clj b/src/scm.clj
index 2bf1249..2071e00 100644
--- a/src/scm.clj
+++ b/src/scm.clj
@@ -11,22 +11,28 @@
 ;;; syntax objects
 
 (defprotocol ISyntax
-  (stx-datum [this])
-  (stx-context [this]))
+  (syntax-e [this])
+  (syntax-context [this]))
 
 (defn syntax? [x]
-  (instance? ISyntax x))
+  (satisfies? ISyntax x))
 
 (deftype Syntax [datum ctx]
   Object
   (equals [x y]
     (or (identical? x y)
-        (and (instance? ISyntax y)
-             (.equals datum (stx-datum y))
-             (.equals ctx (stx-context y)))))
+        (and (satisfies? ISyntax y)
+             (.equals datum (syntax-e y))
+             (.equals ctx (syntax-context y)))))
   ISyntax
-  (stx-datum [this] datum)
-  (stx-context [this] ctx))
+  (syntax-e [this] datum)
+  (syntax-context [this] ctx))
+
+(defn unresolved? [stx]
+  (= (syntax-context stx) ::unresolved))
+
+(defn resolved? [stx]
+  (not (unresolved? stx)))
 
 (def ^:dynamic *print-ctx?* true)
 
@@ -35,26 +41,39 @@
   (binding [*out* writer]
     (pr (tagged-literal
          'scm/stx
-         (if *print-ctx?*
-           [(stx-datum this) (stx-context this)]
-           (stx-datum this))))))
+         (if (and *print-ctx?* (resolved? this))
+           [(syntax-e this) (syntax-context this)]
+           (syntax-e this))))))
 
 (defmethod clojure.pprint/simple-dispatch Syntax [x]
   (clojure.pprint/simple-dispatch
    (tagged-literal
     'scm/stx
-    (if *print-ctx?*
-      [(stx-datum x) (stx-context x)]
-      (stx-datum x)))))
+    (if (and *print-ctx?* (resolved? x))
+      [(syntax-e x) (syntax-context x)]
+      (syntax-e x)))))
 
-(defn stx-reader [[datum ctx]]
-  (->Syntax datum ctx))
+(defn stx-reader [x]
+  (if-let [[datum ctx] (and (vector? x) x)]
+    (->Syntax datum ctx)
+    (->Syntax x ::unresolved)))
 
 (defn datum->syntax
   ([datum]
-   (->Syntax datum nil))
+   (->Syntax datum ::unresolved))
   ([datum ctxt-donor]
-   (->Syntax datum (stx-context ctxt-donor))))
+   (->Syntax datum (syntax-context ctxt-donor))))
+
+(defn identifier?
+  "x가 신택스이고 x의 내용이 심볼이면 true를 생선함."
+  [x]
+  (and (syntax? x) (-> x syntax-e symbol?)))
+
+(defn constant? [x]
+  (or (and (syntax? x) (-> x syntax-e constant?))
+      (number? x)
+      (string? x)
+      (boolean? x)))
 
 
 ;;; improper list
@@ -120,7 +139,7 @@
         ;; 과정할 수 있었더다. 작업 한 개만으로 syntax object들 다
         ;; 만들 수 있어서 이럼은 더 좋다.
         :datum (fn [x]
-                 (->Syntax x ::no-scopes))
+                 (datum->syntax x))
         :number identity
         :symbol symbol
         :string (fn [& els]