diff --git a/include/picconf.h b/include/picconf.h
index 3a2e6887..e3c1388e 100644
--- a/include/picconf.h
+++ b/include/picconf.h
@@ -13,7 +13,7 @@
 #define PIC_STACK_SIZE 1024
 #define PIC_IREP_SIZE 256
 #define PIC_GLOBALS_SIZE 1024
-#define PIC_SYM_TBL_SIZE 128
+#define PIC_SYM_POOL_SIZE 128
 #define PIC_POOL_SIZE 1024
 
 /* enable all debug flags */
diff --git a/include/picrin.h b/include/picrin.h
index 832a0a83..555c86fb 100644
--- a/include/picrin.h
+++ b/include/picrin.h
@@ -27,13 +27,15 @@ typedef struct {
   pic_callinfo *ci;
   pic_callinfo *cibase, *ciend;
 
-  pic_value sDEFINE, sLAMBDA, sIF, sBEGIN, sQUOTE, sSETBANG;
-  pic_value sQUASIQUOTE, sUNQUOTE, sUNQUOTE_SPLICING;
-  pic_value sCONS, sCAR, sCDR, sNILP;
-  pic_value sADD, sSUB, sMUL, sDIV;
-  pic_value sEQ, sLT, sLE, sGT, sGE;
+  pic_sym sDEFINE, sLAMBDA, sIF, sBEGIN, sQUOTE, sSETBANG;
+  pic_sym sQUASIQUOTE, sUNQUOTE, sUNQUOTE_SPLICING;
+  pic_sym sCONS, sCAR, sCDR, sNILP;
+  pic_sym sADD, sSUB, sMUL, sDIV;
+  pic_sym sEQ, sLT, sLE, sGT, sGE;
 
-  struct sym_tbl *sym_tbl;
+  struct xhash *sym_tbl;
+  const char **sym_pool;
+  size_t slen, scapa;
 
   struct xhash *global_tbl;
   pic_value *globals;
@@ -71,8 +73,11 @@ int pic_get_args(pic_state *, const char *, ...);
 void pic_defun(pic_state *, const char *, pic_func_t);
 
 bool pic_eq_p(pic_state *, pic_value, pic_value);
+bool pic_eqv_p(pic_state *, pic_value, pic_value);
+bool pic_equql_p(pic_state *, pic_value, pic_value);
 
-pic_value pic_intern_cstr(pic_state *, const char *);
+pic_sym pic_intern_cstr(pic_state *, const char *);
+const char *pic_symbol_name(pic_state *, pic_sym);
 
 pic_value pic_str_new(pic_state *, const char *, size_t);
 pic_value pic_str_new_cstr(pic_state *, const char *);
diff --git a/include/picrin/symbol.h b/include/picrin/symbol.h
deleted file mode 100644
index a84a6e21..00000000
--- a/include/picrin/symbol.h
+++ /dev/null
@@ -1,11 +0,0 @@
-#ifndef SYMBOL_H__
-#define SYMBOL_H__
-
-struct sym_tbl {
-  pic_value tbl[PIC_SYM_TBL_SIZE];
-  size_t size;
-};
-
-pic_value sym_tbl_get(struct sym_tbl *, const char *);
-
-#endif
diff --git a/include/picrin/value.h b/include/picrin/value.h
index 8474710b..08caa40f 100644
--- a/include/picrin/value.h
+++ b/include/picrin/value.h
@@ -1,6 +1,8 @@
 #ifndef VALUE_H__
 #define VALUE_H__
 
+typedef int pic_sym;
+
 enum pic_vtype {
   PIC_VTYPE_NIL,
   PIC_VTYPE_TRUE,
@@ -8,6 +10,7 @@ enum pic_vtype {
   PIC_VTYPE_UNDEF,
   PIC_VTYPE_FLOAT,
   PIC_VTYPE_INT,
+  PIC_VTYPE_SYMBOL,
   PIC_VTYPE_EOF,
   PIC_VTYPE_HEAP
 };
@@ -18,6 +21,7 @@ typedef struct {
     void *data;
     double f;
     int i;
+    pic_sym sym;
   } u;
 } pic_value;
 
@@ -27,11 +31,11 @@ enum pic_tt {
   PIC_TT_BOOL,
   PIC_TT_FLOAT,
   PIC_TT_INT,
+  PIC_TT_SYMBOL,
   PIC_TT_EOF,
   PIC_TT_UNDEF,
   /* heap */
   PIC_TT_PAIR,
-  PIC_TT_SYMBOL,
   PIC_TT_PROC,
   PIC_TT_PORT,
   PIC_TT_STRING,
@@ -51,11 +55,6 @@ struct pic_pair {
   pic_value cdr;
 };
 
-struct pic_symbol {
-  PIC_OBJECT_HEADER
-  char *name;
-};
-
 struct pic_string {
   PIC_OBJECT_HEADER
   char *str;
@@ -67,7 +66,6 @@ struct pic_port;
 
 #define pic_obj_ptr(o) ((struct pic_object *)o.u.data)
 #define pic_pair_ptr(o) ((struct pic_pair *)o.u.data)
-#define pic_symbol_ptr(o) ((struct pic_symbol *)o.u.data)
 #define pic_str_ptr(v) ((struct pic_string *)v.u.data)
 
 enum pic_tt pic_type(pic_value);
@@ -80,9 +78,11 @@ pic_value pic_undef_value();
 pic_value pic_obj_value(void *);
 pic_value pic_float_value(double);
 pic_value pic_int_value(int);
+pic_value pic_symbol_value(pic_sym);
 
 #define pic_float(v) ((v).u.f)
 #define pic_int(v) ((v).u.i)
+#define pic_sym(v) ((v).u.sym)
 
 #define pic_nil_p(v) ((v).type == PIC_VTYPE_NIL)
 #define pic_true_p(v) ((v).type == PIC_VTYPE_TRUE)
@@ -90,8 +90,8 @@ pic_value pic_int_value(int);
 #define pic_undef_p(v) ((v).type == PIC_VTYPE_UNDEF)
 #define pic_float_p(v) ((v).type == PIC_VTYPE_FLOAT)
 #define pic_int_p(v) ((v).type == PIC_VTYPE_INT)
+#define pic_symbol_p(v) ((v).type == PIC_VTYPE_SYMBOL)
 #define pic_pair_p(v) (pic_type(v) == PIC_TT_PAIR)
-#define pic_symbol_p(v) (pic_type(v) == PIC_TT_SYMBOL)
 #define pic_str_p(v) (pic_type(v) == PIC_TT_STRING)
 
 #endif
diff --git a/src/bool.c b/src/bool.c
index 889f70ce..ea71a61f 100644
--- a/src/bool.c
+++ b/src/bool.c
@@ -12,7 +12,7 @@ pic_eq_p(pic_state *pic, pic_value x, pic_value y)
   case PIC_TT_NIL:
     return true;
   case PIC_TT_SYMBOL:
-    return pic_symbol_ptr(x) == pic_symbol_ptr(y);
+    return pic_sym(x) == pic_sym(y);
   default:
     return false;
   }
diff --git a/src/codegen.c b/src/codegen.c
index 7a3567ff..d6f614a5 100644
--- a/src/codegen.c
+++ b/src/codegen.c
@@ -51,14 +51,14 @@ new_local_scope(pic_state *pic, pic_value args, codegen_scope *scope)
     pic_value sym;
 
     sym = pic_car(pic, v);
-    xh_put(x, pic_symbol_ptr(sym)->name, i++);
+    xh_put(x, pic_symbol_name(pic, pic_sym(sym)), i++);
   }
   if (pic_nil_p(v)) {
     /* pass */
   }
   else if (pic_symbol_p(v)) {
     new_scope->varg = true;
-    xh_put(x, pic_symbol_ptr(v)->name, i);
+    xh_put(x, pic_symbol_name(pic, pic_sym(v)), i);
   }
   else {
     pic_error(pic, "logic flaw");
@@ -179,7 +179,7 @@ codegen(codegen_state *state, pic_value obj)
     int depth, idx;
     const char *name;
 
-    name = pic_symbol_ptr(obj)->name;
+    name = pic_symbol_name(pic, pic_sym(obj));
     s = scope_lookup(state, name, &depth, &idx);
     if (! s) {
       pic_error(pic, "unbound variable");
@@ -213,256 +213,259 @@ codegen(codegen_state *state, pic_value obj)
     }
 
     proc = pic_car(pic, obj);
-    if (pic_eq_p(pic, proc, pic->sDEFINE)) {
-      int idx;
-      pic_value var, val;
+    if (pic_symbol_p(proc)) {
+      pic_sym sym = pic_sym(proc);
 
-      if (pic_length(pic, obj) < 3) {
-	pic_error(pic, "syntax error");
-      }
+      if (sym == pic->sDEFINE) {
+	int idx;
+	pic_value var, val;
 
-      var = pic_car(pic, pic_cdr(pic, obj));
-      if (pic_pair_p(var)) {
-	val = pic_cons(pic, pic->sLAMBDA,
-		       pic_cons(pic, pic_cdr(pic, var),
-				pic_cdr(pic, pic_cdr(pic, obj))));
-	var = pic_car(pic, var);
-      }
-      else {
-	if (pic_length(pic, obj) != 3) {
+	if (pic_length(pic, obj) < 3) {
 	  pic_error(pic, "syntax error");
 	}
-	val = pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj)));
-      }
-      if (! pic_symbol_p(var)) {
-	pic_error(pic, "syntax error");
-      }
 
-      idx = scope_global_define(pic, pic_symbol_ptr(var)->name);
+	var = pic_car(pic, pic_cdr(pic, obj));
+	if (pic_pair_p(var)) {
+	  val = pic_cons(pic, pic_symbol_value(pic->sLAMBDA),
+			 pic_cons(pic, pic_cdr(pic, var),
+				  pic_cdr(pic, pic_cdr(pic, obj))));
+	  var = pic_car(pic, var);
+	}
+	else {
+	  if (pic_length(pic, obj) != 3) {
+	    pic_error(pic, "syntax error");
+	  }
+	  val = pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj)));
+	}
+	if (! pic_symbol_p(var)) {
+	  pic_error(pic, "syntax error");
+	}
 
-      codegen(state, val);
-      irep->code[irep->clen].insn = OP_GSET;
-      irep->code[irep->clen].u.i = idx;
-      irep->clen++;
-      irep->code[irep->clen].insn = OP_PUSHFALSE;
-      irep->clen++;
-      break;
-    }
-    else if (pic_eq_p(pic, proc, pic->sLAMBDA)) {
-      int k = pic->ilen++;
-      irep->code[irep->clen].insn = OP_LAMBDA;
-      irep->code[irep->clen].u.i = k;
-      irep->clen++;
+	idx = scope_global_define(pic, pic_symbol_name(pic, pic_sym(var)));
 
-      pic->irep[k] = codegen_lambda(state, obj);
-      break;
-    }
-    else if (pic_eq_p(pic, proc, pic->sIF)) {
-      int s,t;
-
-      if (pic_length(pic, obj) != 4) {
-	pic_error(pic, "syntax error");
-      }
-
-      codegen(state, pic_car(pic, pic_cdr(pic, obj)));
-
-      irep->code[irep->clen].insn = OP_JMPIF;
-      s = irep->clen++;
-
-      /* if false branch */
-      codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, pic_cdr(pic, obj)))));
-      irep->code[irep->clen].insn = OP_JMP;
-      t = irep->clen++;
-
-      irep->code[s].u.i = irep->clen - s;
-
-      /* if true branch */
-      codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))));
-      irep->code[t].u.i = irep->clen - t;
-      break;
-    }
-    else if (pic_eq_p(pic, proc, pic->sBEGIN)) {
-      pic_value v, seq;
-
-      seq = pic_cdr(pic, obj);
-      for (v = seq; ! pic_nil_p(v); v = pic_cdr(pic, v)) {
-	codegen(state, pic_car(pic, v));
-	irep->code[irep->clen].insn = OP_POP;
-	irep->clen++;
-      }
-      irep->clen--;
-      break;
-    }
-    else if (pic_eq_p(pic, proc, pic->sSETBANG)) {
-      codegen_scope *s;
-      pic_value var;
-      int depth, idx;
-
-      if (pic_length(pic, obj) != 3) {
-	pic_error(pic, "syntax error");
-      }
-
-      var = pic_car(pic, pic_cdr(pic, obj));
-      if (! pic_symbol_p(var)) {
-	pic_error(pic, "syntax error");
-      }
-
-      s = scope_lookup(state, pic_symbol_ptr(var)->name, &depth, &idx);
-      if (! s) {
-	pic_error(pic, "unbound variable");
-      }
-
-      codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))));
-
-      switch (depth) {
-      case -1:			/* global */
+	codegen(state, val);
 	irep->code[irep->clen].insn = OP_GSET;
 	irep->code[irep->clen].u.i = idx;
 	irep->clen++;
+	irep->code[irep->clen].insn = OP_PUSHFALSE;
+	irep->clen++;
 	break;
-      default:			/* nonlocal */
-	/* dirty flag */
-	s->cv_tbl[idx] = 1;
-	/* at this stage, lset and cset are not distinguished */
-	FALLTHROUGH;
-      case 0:			/* local */
-	irep->code[irep->clen].insn = OP_CSET;
-	irep->code[irep->clen].u.c.depth = depth;
-	irep->code[irep->clen].u.c.idx = idx;
+      }
+      else if (sym == pic->sLAMBDA) {
+	int k = pic->ilen++;
+	irep->code[irep->clen].insn = OP_LAMBDA;
+	irep->code[irep->clen].u.i = k;
+	irep->clen++;
+
+	pic->irep[k] = codegen_lambda(state, obj);
+	break;
+      }
+      else if (sym == pic->sIF) {
+	int s,t;
+
+	if (pic_length(pic, obj) != 4) {
+	  pic_error(pic, "syntax error");
+	}
+
+	codegen(state, pic_car(pic, pic_cdr(pic, obj)));
+
+	irep->code[irep->clen].insn = OP_JMPIF;
+	s = irep->clen++;
+
+	/* if false branch */
+	codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, pic_cdr(pic, obj)))));
+	irep->code[irep->clen].insn = OP_JMP;
+	t = irep->clen++;
+
+	irep->code[s].u.i = irep->clen - s;
+
+	/* if true branch */
+	codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))));
+	irep->code[t].u.i = irep->clen - t;
+	break;
+      }
+      else if (sym == pic->sBEGIN) {
+	pic_value v, seq;
+
+	seq = pic_cdr(pic, obj);
+	for (v = seq; ! pic_nil_p(v); v = pic_cdr(pic, v)) {
+	  codegen(state, pic_car(pic, v));
+	  irep->code[irep->clen].insn = OP_POP;
+	  irep->clen++;
+	}
+	irep->clen--;
+	break;
+      }
+      else if (sym == pic->sSETBANG) {
+	codegen_scope *s;
+	pic_value var;
+	int depth, idx;
+
+	if (pic_length(pic, obj) != 3) {
+	  pic_error(pic, "syntax error");
+	}
+
+	var = pic_car(pic, pic_cdr(pic, obj));
+	if (! pic_symbol_p(var)) {
+	  pic_error(pic, "syntax error");
+	}
+
+	s = scope_lookup(state, pic_symbol_name(pic, pic_sym(var)), &depth, &idx);
+	if (! s) {
+	  pic_error(pic, "unbound variable");
+	}
+
+	codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))));
+
+	switch (depth) {
+	case -1:			/* global */
+	  irep->code[irep->clen].insn = OP_GSET;
+	  irep->code[irep->clen].u.i = idx;
+	  irep->clen++;
+	  break;
+	default:			/* nonlocal */
+	  /* dirty flag */
+	  s->cv_tbl[idx] = 1;
+	  /* at this stage, lset and cset are not distinguished */
+	  FALLTHROUGH;
+	case 0:			/* local */
+	  irep->code[irep->clen].insn = OP_CSET;
+	  irep->code[irep->clen].u.c.depth = depth;
+	  irep->code[irep->clen].u.c.idx = idx;
+	  irep->clen++;
+	  break;
+	}
+
+	irep->code[irep->clen].insn = OP_PUSHFALSE;
+	irep->clen++;
+	break;
+      }
+      else if (sym == pic->sQUOTE) {
+	int pidx;
+
+	if (pic_length(pic, obj) != 2) {
+	  pic_error(pic, "syntax error");
+	}
+
+	pidx = pic->plen++;
+	pic->pool[pidx] = pic_car(pic, pic_cdr(pic, obj));
+	irep->code[irep->clen].insn = OP_PUSHCONST;
+	irep->code[irep->clen].u.i = pidx;
 	irep->clen++;
 	break;
       }
 
-      irep->code[irep->clen].insn = OP_PUSHFALSE;
-      irep->clen++;
-      break;
-    }
-    else if (pic_eq_p(pic, proc, pic->sQUOTE)) {
-      int pidx;
-
-      if (pic_length(pic, obj) != 2) {
-	pic_error(pic, "syntax error");
-      }
-
-      pidx = pic->plen++;
-      pic->pool[pidx] = pic_car(pic, pic_cdr(pic, obj));
-      irep->code[irep->clen].insn = OP_PUSHCONST;
-      irep->code[irep->clen].u.i = pidx;
-      irep->clen++;
-      break;
-    }
-
 #define ARGC_ASSERT(n) do {				\
-      if (pic_length(pic, obj) != (n) + 1) {		\
-	pic_error(pic, "wrong number of arguments");	\
-      }							\
-  } while (0)
+	if (pic_length(pic, obj) != (n) + 1) {		\
+	  pic_error(pic, "wrong number of arguments");	\
+	}						\
+      } while (0)
 
-    else if (pic_eq_p(pic, proc, pic->sCONS)) {
-      ARGC_ASSERT(2);
-      codegen(state, pic_car(pic, pic_cdr(pic, obj)));
-      codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))));
-      irep->code[irep->clen].insn = OP_CONS;
-      irep->clen++;
-      break;
-    }
-    else if (pic_eq_p(pic, proc, pic->sCAR)) {
-      ARGC_ASSERT(1);
-      codegen(state, pic_car(pic, pic_cdr(pic, obj)));
-      irep->code[irep->clen].insn = OP_CAR;
-      irep->clen++;
-      break;
-    }
-    else if (pic_eq_p(pic, proc, pic->sCDR)) {
-      ARGC_ASSERT(1);
-      codegen(state, pic_car(pic, pic_cdr(pic, obj)));
-      irep->code[irep->clen].insn = OP_CDR;
-      irep->clen++;
-      break;
-    }
-    else if (pic_eq_p(pic, proc, pic->sNILP)) {
-      ARGC_ASSERT(1);
-      codegen(state, pic_car(pic, pic_cdr(pic, obj)));
-      irep->code[irep->clen].insn = OP_NILP;
-      irep->clen++;
-      break;
-    }
-    else if (pic_eq_p(pic, proc, pic->sADD)) {
-      ARGC_ASSERT(2);
-      codegen(state, pic_car(pic, pic_cdr(pic, obj)));
-      codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))));
-      irep->code[irep->clen].insn = OP_ADD;
-      irep->clen++;
-      break;
-    }
-    else if (pic_eq_p(pic, proc, pic->sSUB)) {
-      ARGC_ASSERT(2);
-      codegen(state, pic_car(pic, pic_cdr(pic, obj)));
-      codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))));
-      irep->code[irep->clen].insn = OP_SUB;
-      irep->clen++;
-      break;
-    }
-    else if (pic_eq_p(pic, proc, pic->sMUL)) {
-      ARGC_ASSERT(2);
-      codegen(state, pic_car(pic, pic_cdr(pic, obj)));
-      codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))));
-      irep->code[irep->clen].insn = OP_MUL;
-      irep->clen++;
-      break;
-    }
-    else if (pic_eq_p(pic, proc, pic->sDIV)) {
-      ARGC_ASSERT(2);
-      codegen(state, pic_car(pic, pic_cdr(pic, obj)));
-      codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))));
-      irep->code[irep->clen].insn = OP_DIV;
-      irep->clen++;
-      break;
-    }
-    else if (pic_eq_p(pic, proc, pic->sEQ)) {
-      ARGC_ASSERT(2);
-      codegen(state, pic_car(pic, pic_cdr(pic, obj)));
-      codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))));
-      irep->code[irep->clen].insn = OP_EQ;
-      irep->clen++;
-      break;
-    }
-    else if (pic_eq_p(pic, proc, pic->sLT)) {
-      ARGC_ASSERT(2);
-      codegen(state, pic_car(pic, pic_cdr(pic, obj)));
-      codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))));
-      irep->code[irep->clen].insn = OP_LT;
-      irep->clen++;
-      break;
-    }
-    else if (pic_eq_p(pic, proc, pic->sLE)) {
-      ARGC_ASSERT(2);
-      codegen(state, pic_car(pic, pic_cdr(pic, obj)));
-      codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))));
-      irep->code[irep->clen].insn = OP_LE;
-      irep->clen++;
-      break;
-    }
-    else if (pic_eq_p(pic, proc, pic->sGT)) {
-      ARGC_ASSERT(2);
-      codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))));
-      codegen(state, pic_car(pic, pic_cdr(pic, obj)));
-      irep->code[irep->clen].insn = OP_LT;
-      irep->clen++;
-      break;
-    }
-    else if (pic_eq_p(pic, proc, pic->sGE)) {
-      ARGC_ASSERT(2);
-      codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))));
-      codegen(state, pic_car(pic, pic_cdr(pic, obj)));
-      irep->code[irep->clen].insn = OP_LE;
-      irep->clen++;
-      break;
-    }
-    else {
-      codegen_call(state, obj);
-      break;
+      else if (sym == pic->sCONS) {
+	ARGC_ASSERT(2);
+	codegen(state, pic_car(pic, pic_cdr(pic, obj)));
+	codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))));
+	irep->code[irep->clen].insn = OP_CONS;
+	irep->clen++;
+	break;
+      }
+      else if (sym == pic->sCAR) {
+	ARGC_ASSERT(1);
+	codegen(state, pic_car(pic, pic_cdr(pic, obj)));
+	irep->code[irep->clen].insn = OP_CAR;
+	irep->clen++;
+	break;
+      }
+      else if (sym == pic->sCDR) {
+	ARGC_ASSERT(1);
+	codegen(state, pic_car(pic, pic_cdr(pic, obj)));
+	irep->code[irep->clen].insn = OP_CDR;
+	irep->clen++;
+	break;
+      }
+      else if (sym == pic->sNILP) {
+	ARGC_ASSERT(1);
+	codegen(state, pic_car(pic, pic_cdr(pic, obj)));
+	irep->code[irep->clen].insn = OP_NILP;
+	irep->clen++;
+	break;
+      }
+      else if (sym == pic->sADD) {
+	ARGC_ASSERT(2);
+	codegen(state, pic_car(pic, pic_cdr(pic, obj)));
+	codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))));
+	irep->code[irep->clen].insn = OP_ADD;
+	irep->clen++;
+	break;
+      }
+      else if (sym == pic->sSUB) {
+	ARGC_ASSERT(2);
+	codegen(state, pic_car(pic, pic_cdr(pic, obj)));
+	codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))));
+	irep->code[irep->clen].insn = OP_SUB;
+	irep->clen++;
+	break;
+      }
+      else if (sym == pic->sMUL) {
+	ARGC_ASSERT(2);
+	codegen(state, pic_car(pic, pic_cdr(pic, obj)));
+	codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))));
+	irep->code[irep->clen].insn = OP_MUL;
+	irep->clen++;
+	break;
+      }
+      else if (sym == pic->sDIV) {
+	ARGC_ASSERT(2);
+	codegen(state, pic_car(pic, pic_cdr(pic, obj)));
+	codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))));
+	irep->code[irep->clen].insn = OP_DIV;
+	irep->clen++;
+	break;
+      }
+      else if (sym == pic->sEQ) {
+	ARGC_ASSERT(2);
+	codegen(state, pic_car(pic, pic_cdr(pic, obj)));
+	codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))));
+	irep->code[irep->clen].insn = OP_EQ;
+	irep->clen++;
+	break;
+      }
+      else if (sym == pic->sLT) {
+	ARGC_ASSERT(2);
+	codegen(state, pic_car(pic, pic_cdr(pic, obj)));
+	codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))));
+	irep->code[irep->clen].insn = OP_LT;
+	irep->clen++;
+	break;
+      }
+      else if (sym == pic->sLE) {
+	ARGC_ASSERT(2);
+	codegen(state, pic_car(pic, pic_cdr(pic, obj)));
+	codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))));
+	irep->code[irep->clen].insn = OP_LE;
+	irep->clen++;
+	break;
+      }
+      else if (sym == pic->sGT) {
+	ARGC_ASSERT(2);
+	codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))));
+	codegen(state, pic_car(pic, pic_cdr(pic, obj)));
+	irep->code[irep->clen].insn = OP_LT;
+	irep->clen++;
+	break;
+      }
+      else if (sym == pic->sGE) {
+	ARGC_ASSERT(2);
+	codegen(state, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))));
+	codegen(state, pic_car(pic, pic_cdr(pic, obj)));
+	irep->code[irep->clen].insn = OP_LE;
+	irep->clen++;
+	break;
+      }
     }
+
+    codegen_call(state, obj);
+    break;
   }
   case PIC_TT_BOOL: {
     if (pic_true_p(obj)) {
diff --git a/src/gc.c b/src/gc.c
index d3b5ce43..40776471 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -4,7 +4,6 @@
 #include "picrin/gc.h"
 #include "picrin/irep.h"
 #include "picrin/proc.h"
-#include "picrin/symbol.h"
 #include "picrin/port.h"
 
 #if GC_DEBUG
@@ -156,9 +155,6 @@ gc_mark_object(pic_state *pic, struct pic_object *obj)
     gc_mark(pic, ((struct pic_pair *)obj)->cdr);
     break;
   }
-  case PIC_TT_SYMBOL: {
-    break;
-  }
   case PIC_TT_ENV: {
     struct pic_env *env = (struct pic_env *)obj;
     int i;
@@ -186,6 +182,7 @@ gc_mark_object(pic_state *pic, struct pic_object *obj)
   case PIC_TT_BOOL:
   case PIC_TT_FLOAT:
   case PIC_TT_INT:
+  case PIC_TT_SYMBOL:
   case PIC_TT_EOF:
   case PIC_TT_UNDEF:
     pic_abort(pic, "logic flaw");
@@ -214,7 +211,6 @@ gc_mark_phase(pic_state *pic)
   for (stack = pic->stbase; stack != pic->sp; ++stack) {
     gc_mark(pic, *stack);
   }
-  gc_mark(pic, *stack);
 
   /* arena */
   for (i = 0; i < pic->arena_idx; ++i) {
@@ -230,34 +226,6 @@ gc_mark_phase(pic_state *pic)
   for (i = 0; i < pic->plen; ++i) {
     gc_mark(pic, pic->pool[i]);
   }
-
-  /* symbol table */
-  for (i = 0; i < pic->sym_tbl->size; ++i) {
-    gc_mark(pic, pic->sym_tbl->tbl[i]);
-  }
-
-  gc_mark(pic, pic->sDEFINE);
-  gc_mark(pic, pic->sLAMBDA);
-  gc_mark(pic, pic->sIF);
-  gc_mark(pic, pic->sBEGIN);
-  gc_mark(pic, pic->sSETBANG);
-  gc_mark(pic, pic->sQUOTE);
-  gc_mark(pic, pic->sQUASIQUOTE);
-  gc_mark(pic, pic->sUNQUOTE);
-  gc_mark(pic, pic->sUNQUOTE_SPLICING);
-  gc_mark(pic, pic->sCONS);
-  gc_mark(pic, pic->sCAR);
-  gc_mark(pic, pic->sCDR);
-  gc_mark(pic, pic->sNILP);
-  gc_mark(pic, pic->sADD);
-  gc_mark(pic, pic->sSUB);
-  gc_mark(pic, pic->sMUL);
-  gc_mark(pic, pic->sEQ);
-  gc_mark(pic, pic->sLT);
-  gc_mark(pic, pic->sLE);
-  gc_mark(pic, pic->sGT);
-  gc_mark(pic, pic->sGE);
-  gc_mark(pic, pic->sDIV);
 }
 
 static bool
@@ -280,12 +248,6 @@ gc_finalize_object(pic_state *pic, struct pic_object *obj)
 #endif
 
   switch (obj->tt) {
-  case PIC_TT_SYMBOL: {
-    char *name;
-    name = ((struct pic_symbol *)obj)->name;
-    pic_free(pic, name);
-    break;
-  }
   case PIC_TT_PAIR: {
     break;
   }
@@ -311,6 +273,7 @@ gc_finalize_object(pic_state *pic, struct pic_object *obj)
   case PIC_TT_BOOL:
   case PIC_TT_FLOAT:
   case PIC_TT_INT:
+  case PIC_TT_SYMBOL:
   case PIC_TT_EOF:
   case PIC_TT_UNDEF:
     pic_abort(pic, "logic flaw");
diff --git a/src/parse.y b/src/parse.y
index 83cc9bd0..52baa02a 100644
--- a/src/parse.y
+++ b/src/parse.y
@@ -58,7 +58,7 @@ program
 	  }
 	  /* if multiple? */
 	  else {
-	    p->value = pic_cons(p->pic, p->pic->sBEGIN, $1);
+	    p->value = pic_cons(p->pic, pic_symbol_value(p->pic->sBEGIN), $1);
 	  }
 	}
 	| incomplete_program_data
@@ -92,7 +92,7 @@ datum
 simple_datum
 	: tSYMBOL
 	{
-	  $$ = pic_intern_cstr(p->pic, $1);
+	  $$ = pic_symbol_value(pic_intern_cstr(p->pic, $1));
 	  free($1);
 	}
 	| tSTRING
diff --git a/src/port.c b/src/port.c
index b44ee312..debc8018 100644
--- a/src/port.c
+++ b/src/port.c
@@ -27,7 +27,7 @@ write(pic_state *pic, pic_value obj)
     printf(")");
     break;
   case PIC_TT_SYMBOL:
-    printf("%s", pic_symbol_ptr(obj)->name);
+    printf("%s", pic_symbol_name(pic, pic_sym(obj)));
     break;
   case PIC_TT_FLOAT:
     printf("%f", pic_float(obj));
diff --git a/src/state.c b/src/state.c
index f72ea5d3..e040ccde 100644
--- a/src/state.c
+++ b/src/state.c
@@ -3,24 +3,8 @@
 #include "picrin.h"
 #include "picrin/gc.h"
 #include "picrin/proc.h"
-#include "picrin/symbol.h"
 #include "xhash/xhash.h"
 
-struct sym_tbl *
-sym_tbl_new()
-{
-  struct sym_tbl *s_tbl;
-  int i;
-
-  s_tbl = (struct sym_tbl *)malloc(sizeof(struct sym_tbl));
-  s_tbl->size = PIC_SYM_TBL_SIZE;
-
-  for (i = 0; i < PIC_SYM_TBL_SIZE; ++i) {
-    s_tbl->tbl[i] = pic_nil_value();
-  }
-  return s_tbl;
-}
-
 void pic_init_core(pic_state *);
 
 pic_state *
@@ -49,7 +33,10 @@ pic_open(int argc, char *argv[], char **envp)
   init_heap_page(pic->heap);
 
   /* symbol table */
-  pic->sym_tbl = sym_tbl_new();
+  pic->sym_tbl = xh_new();
+  pic->sym_pool = (const char **)malloc(sizeof(const char *) * PIC_SYM_POOL_SIZE);
+  pic->slen = 0;
+  pic->scapa = pic->slen + PIC_SYM_POOL_SIZE;
 
   /* irep */
   pic->irep = (struct pic_irep **)malloc(sizeof(struct pic_irep *) * PIC_IREP_SIZE);
diff --git a/src/symbol.c b/src/symbol.c
index f9d67a54..e6d98b13 100644
--- a/src/symbol.c
+++ b/src/symbol.c
@@ -2,65 +2,27 @@
 #include <stdlib.h>
 
 #include "picrin.h"
-#include "picrin/pair.h"
-#include "picrin/symbol.h"
+#include "xhash/xhash.h"
 
-static int
-str_hash(const char *str)
-{
-  int hash = 0, len, i;
-
-  len = strlen(str);
-  for (i = 0; i < len; ++i) {
-    hash = hash * 31 + str[i];
-  }
-  return hash;
-}
-
-pic_value
-sym_tbl_get(struct sym_tbl *s_tbl, const char *key)
-{
-  int hash, idx;
-  pic_value v, k;
-  char *name;
-
-  hash = str_hash(key);
-  idx = hash % s_tbl->size;
-  for (v = s_tbl->tbl[idx]; ! pic_nil_p(v); v = pic_pair_ptr(v)->cdr) {
-    k = pic_pair_ptr(v)->car;
-
-    name = pic_symbol_ptr(k)->name;
-    if (strcmp(name, key) == 0) {
-      return k;
-    }
-  }
-  return pic_undef_value();
-}
-
-pic_value
+pic_sym
 pic_intern_cstr(pic_state *pic, const char *str)
 {
-  pic_value v;
-  int len, hash, idx;
-  char *new_str;
-  struct pic_symbol *sym;
+  struct xh_entry *e;
+  pic_sym id;
 
-  v = sym_tbl_get(pic->sym_tbl, str);
-  if (! pic_undef_p(v)) {
-    return v;
+  e = xh_get(pic->sym_tbl, str);
+  if (e) {
+    return e->val;
   }
 
-  /* clone name string */
-  len = strlen(str);
-  new_str = (char *)pic_alloc(pic, len + 1);
-  strncpy(new_str, str, len + 1);
-
-  sym = (struct pic_symbol*)pic_obj_alloc(pic, sizeof(struct pic_symbol), PIC_TT_SYMBOL);
-  sym->name = new_str;
-  v = pic_obj_value(sym);
-
-  hash = str_hash(str);
-  idx = hash % pic->sym_tbl->size;
-  pic->sym_tbl->tbl[idx] = pic_cons(pic, v, pic->sym_tbl->tbl[idx]);
-  return v;
+  id = pic->slen++;
+  pic->sym_pool[id] = strdup(str);
+  xh_put(pic->sym_tbl, str, id);
+  return id;
+}
+
+const char *
+pic_symbol_name(pic_state *pic, pic_sym sym)
+{
+  return pic->sym_pool[sym];
 }
diff --git a/src/value.c b/src/value.c
index ad6e741d..8aaa60d2 100644
--- a/src/value.c
+++ b/src/value.c
@@ -19,6 +19,8 @@ pic_type(pic_value v)
     return PIC_TT_FLOAT;
   case PIC_VTYPE_INT:
     return PIC_TT_INT;
+  case PIC_VTYPE_SYMBOL:
+    return PIC_TT_SYMBOL;
   case PIC_VTYPE_EOF:
     return PIC_TT_EOF;
   case PIC_VTYPE_HEAP:
@@ -98,6 +100,16 @@ pic_int_value(int i)
   return v;
 }
 
+pic_value
+pic_symbol_value(pic_sym sym)
+{
+  pic_value v;
+
+  v.type = PIC_VTYPE_SYMBOL;
+  v.u.sym = sym;
+  return v;
+}
+
 pic_value
 pic_undef_value()
 {