From f89a55c08211efe58937e5793e1480d73e53d06b Mon Sep 17 00:00:00 2001
From: Yuichi Nishiwaki <yuichi.nishiwaki@gmail.com>
Date: Sun, 21 Feb 2016 04:34:26 +0900
Subject: [PATCH] remove pre-interned symbols

---
 extlib/benz/eval.c                         | 104 ++++++++++-----------
 extlib/benz/gc.c                           |  13 +--
 extlib/benz/include/picrin/private/gc.h    |   2 -
 extlib/benz/include/picrin/private/state.h |   8 --
 extlib/benz/lib.c                          |  10 +-
 extlib/benz/macro.c                        |  17 ++--
 extlib/benz/read.c                         |  20 ++--
 extlib/benz/state.c                        |  53 +----------
 extlib/benz/symbol.c                       |   2 +-
 extlib/benz/write.c                        |  19 ++--
 10 files changed, 95 insertions(+), 153 deletions(-)

diff --git a/extlib/benz/eval.c b/extlib/benz/eval.c
index c0aa5548..1f3ac784 100644
--- a/extlib/benz/eval.c
+++ b/extlib/benz/eval.c
@@ -8,6 +8,9 @@
 #include "picrin/private/opcode.h"
 #include "picrin/private/state.h"
 
+#define EQ(sym, lit) (strcmp(pic_str(pic, pic_sym_name(pic, sym)), lit) == 0)
+#define S(lit) (pic_intern_lit(pic, lit))
+
 static pic_value
 optimize_beta(pic_state *pic, pic_value expr)
 {
@@ -23,10 +26,10 @@ optimize_beta(pic_state *pic, pic_value expr)
   if (pic_sym_p(pic, pic_list_ref(pic, expr, 0))) {
     pic_value sym = pic_list_ref(pic, expr, 0);
 
-    if (pic_eq_p(pic, sym, pic->sQUOTE)) {
+    if (EQ(sym, "quote")) {
       return expr;
-    } else if (pic_eq_p(pic, sym, pic->sLAMBDA)) {
-      return pic_list(pic, 3, pic->sLAMBDA, pic_list_ref(pic, expr, 1), optimize_beta(pic, pic_list_ref(pic, expr, 2)));
+    } else if (EQ(sym, "lambda")) {
+      return pic_list(pic, 3, S("lambda"), pic_list_ref(pic, expr, 1), optimize_beta(pic, pic_list_ref(pic, expr, 2)));
     }
   }
 
@@ -40,7 +43,7 @@ optimize_beta(pic_state *pic, pic_value expr)
   pic_protect(pic, expr);
 
   functor = pic_list_ref(pic, expr, 0);
-  if (pic_pair_p(pic, functor) && pic_eq_p(pic, pic_car(pic, functor), pic->sLAMBDA)) {
+  if (pic_pair_p(pic, functor) && EQ(pic_car(pic, functor), "lambda")) {
     formals = pic_list_ref(pic, functor, 1);
     if (! pic_list_p(pic, formals))
       goto exit;              /* TODO: support ((lambda args x) 1 2) */
@@ -49,12 +52,12 @@ optimize_beta(pic_state *pic, pic_value expr)
       goto exit;
     defs = pic_nil_value(pic);
     pic_for_each (val, args, it) {
-      pic_push(pic, pic_list(pic, 3, pic->sDEFINE, pic_car(pic, formals), val), defs);
+      pic_push(pic, pic_list(pic, 3, S("define"), pic_car(pic, formals), val), defs);
       formals = pic_cdr(pic, formals);
     }
     expr = pic_list_ref(pic, functor, 2);
     pic_for_each (val, defs, it) {
-      expr = pic_list(pic, 3, pic->sBEGIN, val, expr);
+      expr = pic_list(pic, 3, S("begin"), val, expr);
     }
   }
  exit:
@@ -159,11 +162,6 @@ define_var(pic_state *pic, analyze_scope *scope, pic_value sym)
 static pic_value analyze(pic_state *, analyze_scope *, pic_value);
 static pic_value analyze_lambda(pic_state *, analyze_scope *, pic_value);
 
-#define GREF pic_intern_lit(pic, "gref")
-#define LREF pic_intern_lit(pic, "lref")
-#define CREF pic_intern_lit(pic, "cref")
-#define CALL pic_intern_lit(pic, "call")
-
 static pic_value
 analyze_var(pic_state *pic, analyze_scope *scope, pic_value sym)
 {
@@ -172,11 +170,11 @@ analyze_var(pic_state *pic, analyze_scope *scope, pic_value sym)
   depth = find_var(pic, scope, sym);
 
   if (depth == scope->depth) {
-    return pic_list(pic, 2, GREF, sym);
+    return pic_list(pic, 2, S("gref"), sym);
   } else if (depth == 0) {
-    return pic_list(pic, 2, LREF, sym);
+    return pic_list(pic, 2, S("lref"), sym);
   } else {
-    return pic_list(pic, 3, CREF, pic_int_value(pic, depth), sym);
+    return pic_list(pic, 3, S("cref"), pic_int_value(pic, depth), sym);
   }
 }
 
@@ -255,7 +253,7 @@ analyze_lambda(pic_state *pic, analyze_scope *up, pic_value form)
 
   analyzer_scope_destroy(pic, scope);
 
-  return pic_list(pic, 6, pic->sLAMBDA, rest, args, locals, captures, body);
+  return pic_list(pic, 6, S("lambda"), rest, args, locals, captures, body);
 }
 
 static pic_value
@@ -281,7 +279,7 @@ analyze_define(pic_state *pic, analyze_scope *scope, pic_value obj)
 static pic_value
 analyze_call(pic_state *pic, analyze_scope *scope, pic_value obj)
 {
-  return pic_cons(pic, CALL, analyze_list(pic, scope, obj));
+  return pic_cons(pic, S("call"), analyze_list(pic, scope, obj));
 }
 
 static pic_value
@@ -302,16 +300,16 @@ analyze_node(pic_state *pic, analyze_scope *scope, pic_value obj)
     if (pic_sym_p(pic, proc)) {
       pic_value sym = proc;
 
-      if (pic_eq_p(pic, sym, pic->sDEFINE)) {
+      if (EQ(sym, "define")) {
         return analyze_define(pic, scope, obj);
       }
-      else if (pic_eq_p(pic, sym, pic->sLAMBDA)) {
+      else if (EQ(sym, "lambda")) {
         return analyze_defer(pic, scope, obj);
       }
-      else if (pic_eq_p(pic, sym, pic->sQUOTE)) {
+      else if (EQ(sym, "quote")) {
         return obj;
       }
-      else if (pic_eq_p(pic, sym, pic->sBEGIN) || pic_eq_p(pic, sym, pic->sSETBANG) || pic_eq_p(pic, sym, pic->sIF)) {
+      else if (EQ(sym, "begin") || EQ(sym, "set!") || EQ(sym, "if")) {
         return pic_cons(pic, pic_car(pic, obj), analyze_list(pic, scope, pic_cdr(pic, obj)));
       }
     }
@@ -319,7 +317,7 @@ analyze_node(pic_state *pic, analyze_scope *scope, pic_value obj)
     return analyze_call(pic, scope, obj);
   }
   default:
-    return pic_list(pic, 2, pic->sQUOTE, obj);
+    return pic_list(pic, 2, S("quote"), obj);
   }
 }
 
@@ -547,14 +545,14 @@ codegen_ref(pic_state *pic, codegen_context *cxt, pic_value obj, bool tailpos)
   pic_value sym;
 
   sym = pic_car(pic, obj);
-  if (pic_eq_p(pic, sym, GREF)) {
+  if (EQ(sym, "gref")) {
     pic_value name;
 
     name = pic_list_ref(pic, obj, 1);
     emit_i(pic, cxt, OP_GREF, index_global(pic, cxt, name));
     emit_ret(pic, cxt, tailpos);
   }
-  else if (pic_eq_p(pic, sym, CREF)) {
+  else if (EQ(sym, "cref")) {
     pic_value name;
     int depth;
 
@@ -563,7 +561,7 @@ codegen_ref(pic_state *pic, codegen_context *cxt, pic_value obj, bool tailpos)
     emit_r(pic, cxt, OP_CREF, depth, index_capture(pic, cxt, name, depth));
     emit_ret(pic, cxt, tailpos);
   }
-  else if (pic_eq_p(pic, sym, LREF)) {
+  else if (EQ(sym, "lref")) {
     pic_value name;
     int i;
 
@@ -589,14 +587,14 @@ codegen_set(pic_state *pic, codegen_context *cxt, pic_value obj, bool tailpos)
 
   var = pic_list_ref(pic, obj, 1);
   type = pic_list_ref(pic, var, 0);
-  if (pic_eq_p(pic, type, GREF)) {
+  if (EQ(type, "gref")) {
     pic_value name;
 
     name = pic_list_ref(pic, var, 1);
     emit_i(pic, cxt, OP_GSET, index_global(pic, cxt, name));
     emit_ret(pic, cxt, tailpos);
   }
-  else if (pic_eq_p(pic, type, CREF)) {
+  else if (EQ(type, "cref")) {
     pic_value name;
     int depth;
 
@@ -605,7 +603,7 @@ codegen_set(pic_state *pic, codegen_context *cxt, pic_value obj, bool tailpos)
     emit_r(pic, cxt, OP_CSET, depth, index_capture(pic, cxt, name, depth));
     emit_ret(pic, cxt, tailpos);
   }
-  else if (pic_eq_p(pic, type, LREF)) {
+  else if (EQ(type, "lref")) {
     pic_value name;
     int i;
 
@@ -730,8 +728,8 @@ codegen_quote(pic_state *pic, codegen_context *cxt, pic_value obj, bool tailpos)
   emit_ret(pic, cxt, tailpos);
 }
 
-#define VM(uid, op)                             \
-  if (pic_eq_p(pic, sym, uid)) {                \
+#define VM(name, op)                            \
+  if (EQ(sym, name)) {                          \
     emit_i(pic, cxt, op, len - 1);              \
     emit_ret(pic, cxt, tailpos);                \
     return;                                     \
@@ -748,27 +746,27 @@ codegen_call(pic_state *pic, codegen_context *cxt, pic_value obj, bool tailpos)
   }
 
   functor = pic_list_ref(pic, obj, 1);
-  if (pic_eq_p(pic, pic_list_ref(pic, functor, 0), GREF)) {
+  if (EQ(pic_list_ref(pic, functor, 0), "gref")) {
     pic_value sym;
 
     sym = pic_list_ref(pic, functor, 1);
 
-    VM(pic->sCONS, OP_CONS)
-    VM(pic->sCAR, OP_CAR)
-    VM(pic->sCDR, OP_CDR)
-    VM(pic->sNILP, OP_NILP)
-    VM(pic->sSYMBOLP, OP_SYMBOLP)
-    VM(pic->sPAIRP, OP_PAIRP)
-    VM(pic->sNOT, OP_NOT)
-    VM(pic->sEQ, OP_EQ)
-    VM(pic->sLT, OP_LT)
-    VM(pic->sLE, OP_LE)
-    VM(pic->sGT, OP_GT)
-    VM(pic->sGE, OP_GE)
-    VM(pic->sADD, OP_ADD)
-    VM(pic->sSUB, OP_SUB)
-    VM(pic->sMUL, OP_MUL)
-    VM(pic->sDIV, OP_DIV)
+    VM("cons", OP_CONS)
+    VM("car", OP_CAR)
+    VM("cdr", OP_CDR)
+    VM("null?", OP_NILP)
+    VM("symbol?", OP_SYMBOLP)
+    VM("pair?", OP_PAIRP)
+    VM("not", OP_NOT)
+    VM("=", OP_EQ)
+    VM("<", OP_LT)
+    VM("<=", OP_LE)
+    VM(">", OP_GT)
+    VM(">=", OP_GE)
+    VM("+", OP_ADD)
+    VM("-", OP_SUB)
+    VM("*", OP_MUL)
+    VM("/", OP_DIV)
   }
 
   emit_i(pic, cxt, (tailpos ? OP_TAILCALL : OP_CALL), len - 1);
@@ -780,25 +778,25 @@ codegen(pic_state *pic, codegen_context *cxt, pic_value obj, bool tailpos)
   pic_value sym;
 
   sym = pic_car(pic, obj);
-  if (pic_eq_p(pic, sym, GREF) || pic_eq_p(pic, sym, CREF) || pic_eq_p(pic, sym, LREF)) {
+  if (EQ(sym, "gref") || EQ(sym, "cref") || EQ(sym, "lref")) {
     codegen_ref(pic, cxt, obj, tailpos);
   }
-  else if (pic_eq_p(pic, sym, pic->sSETBANG) || pic_eq_p(pic, sym, pic->sDEFINE)) {
+  else if (EQ(sym, "set!") || EQ(sym, "define")) {
     codegen_set(pic, cxt, obj, tailpos);
   }
-  else if (pic_eq_p(pic, sym, pic->sLAMBDA)) {
+  else if (EQ(sym, "lambda")) {
     codegen_lambda(pic, cxt, obj, tailpos);
   }
-  else if (pic_eq_p(pic, sym, pic->sIF)) {
+  else if (EQ(sym, "if")) {
     codegen_if(pic, cxt, obj, tailpos);
   }
-  else if (pic_eq_p(pic, sym, pic->sBEGIN)) {
+  else if (EQ(sym, "begin")) {
     codegen_begin(pic, cxt, obj, tailpos);
   }
-  else if (pic_eq_p(pic, sym, pic->sQUOTE)) {
+  else if (EQ(sym, "quote")) {
     codegen_quote(pic, cxt, obj, tailpos);
   }
-  else if (pic_eq_p(pic, sym, CALL)) {
+  else if (EQ(sym, "call")) {
     codegen_call(pic, cxt, obj, tailpos);
   }
   else {
diff --git a/extlib/benz/gc.c b/extlib/benz/gc.c
index 4ab029ad..8dc5286b 100644
--- a/extlib/benz/gc.c
+++ b/extlib/benz/gc.c
@@ -416,8 +416,6 @@ gc_mark_object(pic_state *pic, struct pic_object *obj)
   }
 }
 
-#define M(x) gc_mark(pic, pic->x)
-
 static void
 gc_mark_phase(pic_state *pic)
 {
@@ -465,15 +463,6 @@ gc_mark_phase(pic_state *pic)
     }
   }
 
-  /* mark reserved symbols */
-  M(sDEFINE); M(sDEFINE_MACRO); M(sLAMBDA); M(sIF); M(sBEGIN); M(sSETBANG);
-  M(sQUOTE); M(sQUASIQUOTE); M(sUNQUOTE); M(sUNQUOTE_SPLICING);
-  M(sSYNTAX_QUOTE); M(sSYNTAX_QUASIQUOTE); M(sSYNTAX_UNQUOTE); M(sSYNTAX_UNQUOTE_SPLICING);
-  M(sDEFINE_LIBRARY); M(sIMPORT); M(sEXPORT); M(sCOND_EXPAND);
-
-  M(sCONS); M(sCAR); M(sCDR); M(sNILP); M(sSYMBOLP); M(sPAIRP);
-  M(sADD); M(sSUB); M(sMUL); M(sDIV); M(sEQ); M(sLT); M(sLE); M(sGT); M(sGE); M(sNOT);
-
   /* global variables */
   gc_mark(pic, pic->globals);
 
@@ -670,7 +659,7 @@ gc_sweep_phase(pic_state *pic)
     if (! kh_exist(s, it))
       continue;
     sym = kh_val(s, it);
-    if (sym->gc_mark == WHITE) {
+    if (sym && sym->gc_mark == WHITE) {
       kh_del(oblist, s, it);
     }
   }
diff --git a/extlib/benz/include/picrin/private/gc.h b/extlib/benz/include/picrin/private/gc.h
index cc75a127..4e97e4d0 100644
--- a/extlib/benz/include/picrin/private/gc.h
+++ b/extlib/benz/include/picrin/private/gc.h
@@ -9,8 +9,6 @@
 extern "C" {
 #endif
 
-struct pic_heap;
-
 struct pic_heap *pic_heap_open(pic_state *);
 void pic_heap_close(pic_state *, struct pic_heap *);
 
diff --git a/extlib/benz/include/picrin/private/state.h b/extlib/benz/include/picrin/private/state.h
index 0c3e1970..9c311bfd 100644
--- a/extlib/benz/include/picrin/private/state.h
+++ b/extlib/benz/include/picrin/private/state.h
@@ -59,14 +59,6 @@ struct pic_state {
 
   struct pic_lib *lib;
 
-  pic_value sDEFINE, sDEFINE_MACRO, sLAMBDA, sIF, sBEGIN, sSETBANG;
-  pic_value sQUOTE, sQUASIQUOTE, sUNQUOTE, sUNQUOTE_SPLICING;
-  pic_value sSYNTAX_QUOTE, sSYNTAX_QUASIQUOTE;
-  pic_value sSYNTAX_UNQUOTE, sSYNTAX_UNQUOTE_SPLICING;
-  pic_value sDEFINE_LIBRARY, sIMPORT, sEXPORT, sCOND_EXPAND;
-  pic_value sCONS, sCAR, sCDR, sNILP, sSYMBOLP, sPAIRP;
-  pic_value sADD, sSUB, sMUL, sDIV, sEQ, sLT, sLE, sGT, sGE, sNOT;
-
   pic_value features;
 
   khash_t(oblist) oblist;       /* string to symbol */
diff --git a/extlib/benz/lib.c b/extlib/benz/lib.c
index 00ef206c..62823155 100644
--- a/extlib/benz/lib.c
+++ b/extlib/benz/lib.c
@@ -46,11 +46,13 @@ make_library_env(pic_state *pic, pic_value name)
 
   e = pic_obj_value(env);
 
+#define REGISTER(name) pic_put_identifier(pic, pic_intern_lit(pic, name), pic_intern_lit(pic, name), e)
+
   /* set up default environment */
-  pic_put_identifier(pic, pic->sDEFINE_LIBRARY, pic->sDEFINE_LIBRARY, e);
-  pic_put_identifier(pic, pic->sIMPORT, pic->sIMPORT, e);
-  pic_put_identifier(pic, pic->sEXPORT, pic->sEXPORT, e);
-  pic_put_identifier(pic, pic->sCOND_EXPAND, pic->sCOND_EXPAND, e);
+  REGISTER("define-library");
+  REGISTER("import");
+  REGISTER("export");
+  REGISTER("cond-expand");
 
   return e;
 }
diff --git a/extlib/benz/macro.c b/extlib/benz/macro.c
index 0de7e6b5..52a2bad2 100644
--- a/extlib/benz/macro.c
+++ b/extlib/benz/macro.c
@@ -139,6 +139,9 @@ shadow_macro(pic_state *pic, pic_value uid)
 static pic_value expand(pic_state *, pic_value expr, pic_value env, pic_value deferred);
 static pic_value expand_lambda(pic_state *, pic_value expr, pic_value env);
 
+#define EQ(sym, lit) (strcmp(pic_str(pic, pic_sym_name(pic, sym)), lit) == 0)
+#define S(lit) (pic_intern_lit(pic, lit))
+
 static pic_value
 expand_var(pic_state *pic, pic_value id, pic_value env, pic_value deferred)
 {
@@ -155,7 +158,7 @@ expand_var(pic_state *pic, pic_value id, pic_value env, pic_value deferred)
 static pic_value
 expand_quote(pic_state *pic, pic_value expr)
 {
-  return pic_cons(pic, pic->sQUOTE, pic_cdr(pic, expr));
+  return pic_cons(pic, S("quote"), pic_cdr(pic, expr));
 }
 
 static pic_value
@@ -229,7 +232,7 @@ expand_lambda(pic_state *pic, pic_value expr, pic_value env)
 
   expand_deferred(pic, deferred, in);
 
-  return pic_list(pic, 3, pic->sLAMBDA, formal, body);
+  return pic_list(pic, 3, S("lambda"), formal, body);
 }
 
 static pic_value
@@ -245,7 +248,7 @@ expand_define(pic_state *pic, pic_value expr, pic_value env, pic_value deferred)
   }
   val = expand(pic, pic_list_ref(pic, expr, 2), env, deferred);
 
-  return pic_list(pic, 3, pic->sDEFINE, uid, val);
+  return pic_list(pic, 3, S("define"), uid, val);
 }
 
 static pic_value
@@ -289,16 +292,16 @@ expand_node(pic_state *pic, pic_value expr, pic_value env, pic_value deferred)
 
       functor = pic_find_identifier(pic, pic_car(pic, expr), env);
 
-      if (pic_eq_p(pic, functor, pic->sDEFINE_MACRO)) {
+      if (EQ(functor, "define-macro")) {
         return expand_defmacro(pic, expr, env);
       }
-      else if (pic_eq_p(pic, functor, pic->sLAMBDA)) {
+      else if (EQ(functor, "lambda")) {
         return expand_defer(pic, expr, deferred);
       }
-      else if (pic_eq_p(pic, functor, pic->sDEFINE)) {
+      else if (EQ(functor, "define")) {
         return expand_define(pic, expr, env, deferred);
       }
-      else if (pic_eq_p(pic, functor, pic->sQUOTE)) {
+      else if (EQ(functor, "quote")) {
         return expand_quote(pic, expr);
       }
 
diff --git a/extlib/benz/read.c b/extlib/benz/read.c
index 157ef7b2..85f4fbaf 100644
--- a/extlib/benz/read.c
+++ b/extlib/benz/read.c
@@ -151,23 +151,25 @@ read_directive(pic_state *pic, xFILE *file, int c)
 static pic_value
 read_quote(pic_state *pic, xFILE *file, int PIC_UNUSED(c))
 {
-  return pic_list(pic, 2, pic->sQUOTE, read(pic, file, next(pic, file)));
+  return pic_list(pic, 2, pic_intern_lit(pic, "quote"), read(pic, file, next(pic, file)));
 }
 
 static pic_value
 read_quasiquote(pic_state *pic, xFILE *file, int PIC_UNUSED(c))
 {
-  return pic_list(pic, 2, pic->sQUASIQUOTE, read(pic, file, next(pic, file)));
+  return pic_list(pic, 2, pic_intern_lit(pic, "quasiquote"), read(pic, file, next(pic, file)));
 }
 
 static pic_value
 read_unquote(pic_state *pic, xFILE *file, int PIC_UNUSED(c))
 {
-  pic_value tag = pic->sUNQUOTE;
+  pic_value tag;
 
   if (peek(pic, file) == '@') {
-    tag = pic->sUNQUOTE_SPLICING;
+    tag = pic_intern_lit(pic, "unquote-splicing");
     next(pic, file);
+  } else {
+    tag = pic_intern_lit(pic, "unquote");
   }
   return pic_list(pic, 2, tag, read(pic, file, next(pic, file)));
 }
@@ -175,23 +177,25 @@ read_unquote(pic_state *pic, xFILE *file, int PIC_UNUSED(c))
 static pic_value
 read_syntax_quote(pic_state *pic, xFILE *file, int PIC_UNUSED(c))
 {
-  return pic_list(pic, 2, pic->sSYNTAX_QUOTE, read(pic, file, next(pic, file)));
+  return pic_list(pic, 2, pic_intern_lit(pic, "syntax-quote"), read(pic, file, next(pic, file)));
 }
 
 static pic_value
 read_syntax_quasiquote(pic_state *pic, xFILE *file, int PIC_UNUSED(c))
 {
-  return pic_list(pic, 2, pic->sSYNTAX_QUASIQUOTE, read(pic, file, next(pic, file)));
+  return pic_list(pic, 2, pic_intern_lit(pic, "syntax-quasiquote"), read(pic, file, next(pic, file)));
 }
 
 static pic_value
 read_syntax_unquote(pic_state *pic, xFILE *file, int PIC_UNUSED(c))
 {
-  pic_value tag = pic->sSYNTAX_UNQUOTE;
+  pic_value tag;
 
   if (peek(pic, file) == '@') {
-    tag = pic->sSYNTAX_UNQUOTE_SPLICING;
+    tag = pic_intern_lit(pic, "syntax-unquote-splicing");
     next(pic, file);
+  } else {
+    tag = pic_intern_lit(pic, "syntax-unquote");
   }
   return pic_list(pic, 2, tag, read(pic, file, next(pic, file)));
 }
diff --git a/extlib/benz/state.c b/extlib/benz/state.c
index 8ddd9dec..293e13de 100644
--- a/extlib/benz/state.c
+++ b/extlib/benz/state.c
@@ -193,7 +193,6 @@ pic_open(pic_allocf allocf, void *userdata)
   char t;
 
   pic_state *pic;
-  size_t ai;
 
   pic = allocf(userdata, NULL, sizeof(pic_state));
 
@@ -260,10 +259,10 @@ pic_open(pic_allocf allocf, void *userdata)
   pic->ucnt = 0;
 
   /* global variables */
-  pic->globals = pic_make_weak(pic);
+  pic->globals = pic_invalid_value(pic);
 
   /* macros */
-  pic->macros = pic_make_weak(pic);
+  pic->macros = pic_invalid_value(pic);
 
   /* features */
   pic->features = pic_nil_value(pic);
@@ -299,48 +298,6 @@ pic_open(pic_allocf allocf, void *userdata)
   /* native stack marker */
   pic->native_stack_start = &t;
 
-  ai = pic_enter(pic);
-
-#define S(slot,name) pic->slot = pic_intern_lit(pic, name)
-
-  S(sDEFINE, "define");
-  S(sDEFINE_MACRO, "define-macro");
-  S(sLAMBDA, "lambda");
-  S(sIF, "if");
-  S(sBEGIN, "begin");
-  S(sSETBANG, "set!");
-  S(sQUOTE, "quote");
-  S(sQUASIQUOTE, "quasiquote");
-  S(sUNQUOTE, "unquote");
-  S(sUNQUOTE_SPLICING, "unquote-splicing");
-  S(sSYNTAX_QUOTE, "syntax-quote");
-  S(sSYNTAX_QUASIQUOTE, "syntax-quasiquote");
-  S(sSYNTAX_UNQUOTE, "syntax-unquote");
-  S(sSYNTAX_UNQUOTE_SPLICING, "syntax-unquote-splicing");
-  S(sIMPORT, "import");
-  S(sEXPORT, "export");
-  S(sDEFINE_LIBRARY, "define-library");
-  S(sCOND_EXPAND, "cond-expand");
-
-  S(sCONS, "cons");
-  S(sCAR, "car");
-  S(sCDR, "cdr");
-  S(sNILP, "null?");
-  S(sSYMBOLP, "symbol?");
-  S(sPAIRP, "pair?");
-  S(sADD, "+");
-  S(sSUB, "-");
-  S(sMUL, "*");
-  S(sDIV, "/");
-  S(sEQ, "=");
-  S(sLT, "<");
-  S(sLE, "<=");
-  S(sGT, ">");
-  S(sGE, ">=");
-  S(sNOT, "not");
-
-  pic_leave(pic, ai);
-
   /* root tables */
   pic->globals = pic_make_weak(pic);
   pic->macros = pic_make_weak(pic);
@@ -355,20 +312,18 @@ pic_open(pic_allocf allocf, void *userdata)
   pic_reader_init(pic);
 
   /* parameter table */
-  pic->ptable = pic_cons(pic, pic_make_weak(pic), pic->ptable);
+  pic->ptable = pic_cons(pic, pic_make_weak(pic), pic_nil_value(pic));
 
   /* standard libraries */
   pic_make_library(pic, "picrin.user");
   pic_in_library(pic, "picrin.user");
 
-  pic_leave(pic, ai);
-
   /* turn on GC */
   pic->gc_enable = true;
 
   pic_init_core(pic);
 
-  pic_leave(pic, ai);
+  pic_leave(pic, 0);            /* empty arena */
 
   return pic;
 
diff --git a/extlib/benz/symbol.c b/extlib/benz/symbol.c
index 795ce367..bcd7dac0 100644
--- a/extlib/benz/symbol.c
+++ b/extlib/benz/symbol.c
@@ -27,7 +27,7 @@ pic_intern(pic_state *pic, pic_value str)
     return pic_obj_value(sym);
   }
 
-  kh_val(h, it) = pic_sym_ptr(pic, pic->sQUOTE); /* dummy */
+  kh_val(h, it) = NULL;         /* dummy */
 
   sym = (pic_sym *)pic_obj_alloc(pic, offsetof(pic_sym, env), PIC_TYPE_SYMBOL);
   sym->u.str = pic_str_ptr(pic, str);
diff --git a/extlib/benz/write.c b/extlib/benz/write.c
index 382cff61..ffd8f0d5 100644
--- a/extlib/benz/write.c
+++ b/extlib/benz/write.c
@@ -5,7 +5,6 @@
 #include "picrin.h"
 #include "picrin/extra.h"
 #include "picrin/private/object.h"
-#include "picrin/private/state.h"
 
 KHASH_DECLARE(l, void *, int)
 KHASH_DECLARE(v, void *, int)
@@ -170,6 +169,8 @@ write_pair_help(struct writer_control *p, pic_value pair)
   }
 }
 
+#define EQ(sym, lit) (strcmp(pic_str(pic, pic_sym_name(pic, sym)), lit) == 0)
+
 static void
 write_pair(struct writer_control *p, pic_value pair)
 {
@@ -179,42 +180,42 @@ write_pair(struct writer_control *p, pic_value pair)
 
   if (pic_pair_p(pic, pic_cdr(pic, pair)) && pic_nil_p(pic, pic_cddr(pic, pair)) && pic_sym_p(pic, pic_car(pic, pair))) {
     tag = pic_car(pic, pair);
-    if (pic_eq_p(pic, tag, pic->sQUOTE)) {
+    if (EQ(tag, "quote")) {
       xfprintf(pic, file, "'");
       write_core(p, pic_cadr(pic, pair));
       return;
     }
-    else if (pic_eq_p(pic, tag, pic->sUNQUOTE)) {
+    else if (EQ(tag, "unquote")) {
       xfprintf(pic, file, ",");
       write_core(p, pic_cadr(pic, pair));
       return;
     }
-    else if (pic_eq_p(pic, tag, pic->sUNQUOTE_SPLICING)) {
+    else if (EQ(tag, "unquote-splicing")) {
       xfprintf(pic, file, ",@");
       write_core(p, pic_cadr(pic, pair));
       return;
     }
-    else if (pic_eq_p(pic, tag, pic->sQUASIQUOTE)) {
+    else if (EQ(tag, "quasiquote")) {
       xfprintf(pic, file, "`");
       write_core(p, pic_cadr(pic, pair));
       return;
     }
-    else if (pic_eq_p(pic, tag, pic->sSYNTAX_QUOTE)) {
+    else if (EQ(tag, "syntax-quote")) {
       xfprintf(pic, file, "#'");
       write_core(p, pic_cadr(pic, pair));
       return;
     }
-    else if (pic_eq_p(pic, tag, pic->sSYNTAX_UNQUOTE)) {
+    else if (EQ(tag, "syntax-unquote")) {
       xfprintf(pic, file, "#,");
       write_core(p, pic_cadr(pic, pair));
       return;
     }
-    else if (pic_eq_p(pic, tag, pic->sSYNTAX_UNQUOTE_SPLICING)) {
+    else if (EQ(tag, "syntax-unquote-splicing")) {
       xfprintf(pic, file, "#,@");
       write_core(p, pic_cadr(pic, pair));
       return;
     }
-    else if (pic_eq_p(pic, tag, pic->sSYNTAX_QUASIQUOTE)) {
+    else if (EQ(tag, "syntax-quasiquote")) {
       xfprintf(pic, file, "#`");
       write_core(p, pic_cadr(pic, pair));
       return;