diff --git a/eval.c b/eval.c
index 7754a700..d5babf23 100644
--- a/eval.c
+++ b/eval.c
@@ -1230,798 +1230,7 @@ static sexp make_opcode_procedure (sexp ctx, sexp op, sexp_uint_t i) {
   return res;
 }
 
-/*********************** the virtual machine **************************/
-
-static sexp sexp_save_stack (sexp ctx, sexp *stack, sexp_uint_t to) {
-  sexp res, *data;
-  sexp_uint_t i;
-  res = sexp_make_vector(ctx, sexp_make_fixnum(to), SEXP_VOID);
-  data = sexp_vector_data(res);
-  for (i=0; i<to; i++)
-    data[i] = stack[i];
-  return res;
-}
-
-static sexp_uint_t sexp_restore_stack (sexp saved, sexp *current) {
-  sexp_uint_t len = sexp_vector_length(saved), i;
-  sexp *from = sexp_vector_data(saved);
-  for (i=0; i<len; i++)
-    current[i] = from[i];
-  return len;
-}
-
-#define _ARG1 stack[top-1]
-#define _ARG2 stack[top-2]
-#define _ARG3 stack[top-3]
-#define _ARG4 stack[top-4]
-#define _ARG5 stack[top-5]
-#define _ARG6 stack[top-6]
-#define _PUSH(x) (stack[top++]=(x))
-
-#if SEXP_USE_ALIGNED_BYTECODE
-#define _ALIGN_IP() ip = (unsigned char *)sexp_word_align((unsigned long)ip)
-#else
-#define _ALIGN_IP()
-#endif
-
-#define _WORD0 ((sexp*)ip)[0]
-#define _UWORD0 ((sexp_uint_t*)ip)[0]
-#define _SWORD0 ((sexp_sint_t*)ip)[0]
-#define _WORD1 ((sexp*)ip)[1]
-#define _UWORD1 ((sexp_uint_t*)ip)[1]
-#define _SWORD1 ((sexp_sint_t*)ip)[1]
-
-#define sexp_raise(msg, args)                                       \
-  do {sexp_context_top(ctx) = top+1;                                \
-      stack[top] = args;                                            \
-      stack[top] = sexp_user_exception(ctx, self, msg, stack[top]); \
-      top++;                                                        \
-      goto call_error_handler;}                                     \
-  while (0)
-
-#define sexp_check_exception() do {if (sexp_exceptionp(_ARG1)) \
-                                     goto call_error_handler;} \
-                                while (0)
-
-sexp sexp_vm (sexp ctx, sexp proc) {
-  sexp bc = sexp_procedure_code(proc), cp = sexp_procedure_vars(proc);
-  sexp *stack = sexp_stack_data(sexp_context_stack(ctx));
-  unsigned char *ip = sexp_bytecode_data(bc);
-  sexp_sint_t i, j, k, fp, top = sexp_stack_top(sexp_context_stack(ctx));
-#if SEXP_USE_BIGNUMS
-  sexp_lsint_t prod;
-#endif
-  sexp_gc_var3(self, tmp1, tmp2);
-  sexp_gc_preserve3(ctx, self, tmp1, tmp2);
-  fp = top - 4;
-  self = proc;
-
- loop:
-#if SEXP_USE_DEBUG_VM
-  if (sexp_context_tracep(ctx)) {
-    sexp_print_stack(ctx, stack, top, fp, SEXP_FALSE);
-    fprintf(stderr, "%s\n", (*ip<=SEXP_OP_NUM_OPCODES) ?
-            reverse_opcode_names[*ip] : "UNKNOWN");
-  }
-#endif
-  switch (*ip++) {
-  case SEXP_OP_NOOP:
-    break;
-  case SEXP_OP_RAISE:
-  call_error_handler:
-    tmp1 = sexp_cdr(sexp_global(ctx, SEXP_G_ERR_HANDLER));
-    if (! sexp_procedurep(tmp1)) goto end_loop;
-    stack[top] = (sexp) 1;
-    stack[top+1] = sexp_make_fixnum(ip-sexp_bytecode_data(bc));
-    stack[top+2] = self;
-    stack[top+3] = sexp_make_fixnum(fp);
-    top += 4;
-    self = tmp1;
-    bc = sexp_procedure_code(self);
-    ip = sexp_bytecode_data(bc);
-    cp = sexp_procedure_vars(self);
-    fp = top-4;
-    break;
-  case SEXP_OP_RESUMECC:
-    tmp1 = stack[fp-1];
-    top = sexp_restore_stack(sexp_vector_ref(cp, 0), stack);
-    fp = sexp_unbox_fixnum(_ARG1);
-    self = _ARG2;
-    bc = sexp_procedure_code(self);
-    cp = sexp_procedure_vars(self);
-    ip = sexp_bytecode_data(bc) + sexp_unbox_fixnum(_ARG3);
-    i = sexp_unbox_fixnum(_ARG4);
-    top -= 4;
-    _ARG1 = tmp1;
-    break;
-  case SEXP_OP_CALLCC:
-    stack[top] = SEXP_ONE;
-    stack[top+1] = sexp_make_fixnum(ip-sexp_bytecode_data(bc));
-    stack[top+2] = self;
-    stack[top+3] = sexp_make_fixnum(fp);
-    tmp1 = _ARG1;
-    i = 1;
-    sexp_context_top(ctx) = top;
-    tmp2 = sexp_make_vector(ctx, SEXP_ONE, SEXP_UNDEF);
-    sexp_vector_set(tmp2, SEXP_ZERO, sexp_save_stack(ctx, stack, top+4));
-    _ARG1 = sexp_make_procedure(ctx,
-                                SEXP_ZERO,
-                                SEXP_ONE,
-                                sexp_global(ctx, SEXP_G_RESUMECC_BYTECODE),
-                                tmp2);
-    top++;
-    ip -= sizeof(sexp);
-    goto make_call;
-  case SEXP_OP_APPLY1:
-    tmp1 = _ARG1;
-    tmp2 = _ARG2;
-    i = sexp_unbox_fixnum(sexp_length(ctx, tmp2));
-    top += (i-2);
-    for ( ; sexp_pairp(tmp2); tmp2=sexp_cdr(tmp2), top--)
-      _ARG1 = sexp_car(tmp2);
-    top += i+1;
-    ip -= sizeof(sexp);
-    goto make_call;
-  case SEXP_OP_TAIL_CALL:
-    _ALIGN_IP();
-    i = sexp_unbox_fixnum(_WORD0);    /* number of params */
-    tmp1 = _ARG1;                              /* procedure to call */
-    /* save frame info */
-    tmp2 = stack[fp+3];
-    j = sexp_unbox_fixnum(stack[fp]);
-    self = stack[fp+2];
-    bc = sexp_procedure_vars(self);
-    cp = sexp_procedure_vars(self);
-    ip = (sexp_bytecode_data(bc)
-          + sexp_unbox_fixnum(stack[fp+1])) - sizeof(sexp);
-    /* copy new args into place */
-    for (k=0; k<i; k++)
-      stack[fp-j+k] = stack[top-1-i+k];
-    top = fp+i-j+1;
-    fp = sexp_unbox_fixnum(tmp2);
-    goto make_call;
-  case SEXP_OP_CALL:
-#if SEXP_USE_CHECK_STACK
-    if (top+16 >= SEXP_INIT_STACK_SIZE) {
-      _ARG1 = sexp_global(ctx, SEXP_G_OOS_ERROR);
-      goto end_loop;
-    }
-#endif
-    _ALIGN_IP();
-    i = sexp_unbox_fixnum(_WORD0);
-    tmp1 = _ARG1;
-  make_call:
-    if (sexp_opcodep(tmp1)) {
-      /* compile non-inlined opcode applications on the fly */
-      sexp_context_top(ctx) = top;
-      tmp1 = make_opcode_procedure(ctx, tmp1, i);
-      if (sexp_exceptionp(tmp1)) {
-        _ARG1 = tmp1;
-        goto call_error_handler;
-      }
-    }
-    if (! sexp_procedurep(tmp1))
-      sexp_raise("non procedure application", sexp_list1(ctx, tmp1));
-    j = i - sexp_unbox_fixnum(sexp_procedure_num_args(tmp1));
-    if (j < 0)
-      sexp_raise("not enough args",
-                 sexp_list2(ctx, tmp1, sexp_make_fixnum(i)));
-    if (j > 0) {
-      if (sexp_procedure_variadic_p(tmp1)) {
-        stack[top-i-1] = sexp_cons(ctx, stack[top-i-1], SEXP_NULL);
-        for (k=top-i; k<top-(i-j)-1; k++)
-          stack[top-i-1] = sexp_cons(ctx, stack[k], stack[top-i-1]);
-        for ( ; k<top; k++)
-          stack[k-j+1] = stack[k];
-        top -= (j-1);
-        i -= (j-1);
-      } else {
-        sexp_raise("too many args",
-                   sexp_list2(ctx, tmp1, sexp_make_fixnum(i)));
-      }
-    } else if (sexp_procedure_variadic_p(tmp1)) {
-      /* shift stack, set extra arg to null */
-      for (k=top; k>=top-i; k--)
-        stack[k] = stack[k-1];
-      stack[top-i-1] = SEXP_NULL;
-      top++;
-      i++;
-    }
-    _ARG1 = sexp_make_fixnum(i);
-    stack[top] = sexp_make_fixnum(ip+sizeof(sexp)-sexp_bytecode_data(bc));
-    stack[top+1] = self;
-    stack[top+2] = sexp_make_fixnum(fp);
-    top += 3;
-    self = tmp1;
-    bc = sexp_procedure_code(self);
-    ip = sexp_bytecode_data(bc);
-    cp = sexp_procedure_vars(self);
-    fp = top-4;
-    break;
-  case SEXP_OP_FCALL0:
-    _ALIGN_IP();
-    sexp_context_top(ctx) = top;
-    _PUSH(((sexp_proc1)sexp_opcode_func(_WORD0))(ctx sexp_api_pass(_WORD0, 0)));
-    ip += sizeof(sexp);
-    sexp_check_exception();
-    break;
-  case SEXP_OP_FCALL1:
-    _ALIGN_IP();
-    sexp_context_top(ctx) = top;
-    _ARG1 = ((sexp_proc2)sexp_opcode_func(_WORD0))(ctx sexp_api_pass(_WORD0, 1), _ARG1);
-    ip += sizeof(sexp);
-    sexp_check_exception();
-    break;
-  case SEXP_OP_FCALL2:
-    _ALIGN_IP();
-    sexp_context_top(ctx) = top;
-    _ARG2 = ((sexp_proc3)sexp_opcode_func(_WORD0))(ctx sexp_api_pass(_WORD0, 2), _ARG1, _ARG2);
-    top--;
-    ip += sizeof(sexp);
-    sexp_check_exception();
-    break;
-  case SEXP_OP_FCALL3:
-    _ALIGN_IP();
-    sexp_context_top(ctx) = top;
-    _ARG3 = ((sexp_proc4)sexp_opcode_func(_WORD0))(ctx sexp_api_pass(_WORD0, 3), _ARG1, _ARG2, _ARG3);
-    top -= 2;
-    ip += sizeof(sexp);
-    sexp_check_exception();
-    break;
-  case SEXP_OP_FCALL4:
-    _ALIGN_IP();
-    sexp_context_top(ctx) = top;
-    _ARG4 = ((sexp_proc5)sexp_opcode_func(_WORD0))(ctx sexp_api_pass(_WORD0, 4), _ARG1, _ARG2, _ARG3, _ARG4);
-    top -= 3;
-    ip += sizeof(sexp);
-    sexp_check_exception();
-    break;
-  case SEXP_OP_FCALL5:
-    _ALIGN_IP();
-    sexp_context_top(ctx) = top;
-    _ARG5 = ((sexp_proc6)sexp_opcode_func(_WORD0))(ctx sexp_api_pass(_WORD0, 5), _ARG1, _ARG2, _ARG3, _ARG4, _ARG5);
-    top -= 4;
-    ip += sizeof(sexp);
-    sexp_check_exception();
-    break;
-  case SEXP_OP_FCALL6:
-    _ALIGN_IP();
-    sexp_context_top(ctx) = top;
-    _ARG6 = ((sexp_proc7)sexp_opcode_func(_WORD0))(ctx sexp_api_pass(_WORD0, 6), _ARG1, _ARG2, _ARG3, _ARG4, _ARG5, _ARG6);
-    top -= 5;
-    ip += sizeof(sexp);
-    sexp_check_exception();
-    break;
-  case SEXP_OP_JUMP_UNLESS:
-    _ALIGN_IP();
-    if (stack[--top] == SEXP_FALSE)
-      ip += _SWORD0;
-    else
-      ip += sizeof(sexp_sint_t);
-    break;
-  case SEXP_OP_JUMP:
-    _ALIGN_IP();
-    ip += _SWORD0;
-    break;
-  case SEXP_OP_PUSH:
-    _ALIGN_IP();
-    _PUSH(_WORD0);
-    ip += sizeof(sexp);
-    break;
-  case SEXP_OP_DROP:
-    top--;
-    break;
-  case SEXP_OP_GLOBAL_REF:
-    _ALIGN_IP();
-    if (sexp_cdr(_WORD0) == SEXP_UNDEF)
-      sexp_raise("undefined variable", sexp_list1(ctx, sexp_car(_WORD0)));
-    /* ... FALLTHROUGH ... */
-  case SEXP_OP_GLOBAL_KNOWN_REF:
-    _ALIGN_IP();
-    _PUSH(sexp_cdr(_WORD0));
-    ip += sizeof(sexp);
-    break;
-  case SEXP_OP_STACK_REF:            /* `pick' in forth */
-    _ALIGN_IP();
-    stack[top] = stack[top - _SWORD0];
-    ip += sizeof(sexp);
-    top++;
-    break;
-  case SEXP_OP_LOCAL_REF:
-    _ALIGN_IP();
-    stack[top] = stack[fp - 1 - _SWORD0];
-    ip += sizeof(sexp);
-    top++;
-    break;
-  case SEXP_OP_LOCAL_SET:
-    _ALIGN_IP();
-    stack[fp - 1 - _SWORD0] = _ARG1;
-    _ARG1 = SEXP_VOID;
-    ip += sizeof(sexp);
-    break;
-  case SEXP_OP_CLOSURE_REF:
-    _ALIGN_IP();
-    _PUSH(sexp_vector_ref(cp, sexp_make_fixnum(_WORD0)));
-    ip += sizeof(sexp);
-    break;
-  case SEXP_OP_VECTOR_REF:
-    if (! sexp_vectorp(_ARG1))
-      sexp_raise("vector-ref: not a vector", sexp_list1(ctx, _ARG1));
-    else if (! sexp_fixnump(_ARG2))
-      sexp_raise("vector-ref: not an integer", sexp_list1(ctx, _ARG2));
-    i = sexp_unbox_fixnum(_ARG2);
-    if ((i < 0) || (i >= sexp_vector_length(_ARG1)))
-      sexp_raise("vector-ref: index out of range", sexp_list2(ctx, _ARG1, _ARG2));
-    _ARG2 = sexp_vector_ref(_ARG1, _ARG2);
-    top--;
-    break;
-  case SEXP_OP_VECTOR_SET:
-    if (! sexp_vectorp(_ARG1))
-      sexp_raise("vector-set!: not a vector", sexp_list1(ctx, _ARG1));
-    else if (sexp_immutablep(_ARG1))
-      sexp_raise("vector-set!: immutable vector", sexp_list1(ctx, _ARG1));
-    else if (! sexp_fixnump(_ARG2))
-      sexp_raise("vector-set!: not an integer", sexp_list1(ctx, _ARG2));
-    i = sexp_unbox_fixnum(_ARG2);
-    if ((i < 0) || (i >= sexp_vector_length(_ARG1)))
-      sexp_raise("vector-set!: index out of range", sexp_list2(ctx, _ARG1, _ARG2));
-    sexp_vector_set(_ARG1, _ARG2, _ARG3);
-    _ARG3 = SEXP_VOID;
-    top-=2;
-    break;
-  case SEXP_OP_VECTOR_LENGTH:
-    if (! sexp_vectorp(_ARG1))
-      sexp_raise("vector-length: not a vector", sexp_list1(ctx, _ARG1));
-    _ARG1 = sexp_make_fixnum(sexp_vector_length(_ARG1));
-    break;
-  case SEXP_OP_STRING_REF:
-    if (! sexp_stringp(_ARG1))
-      sexp_raise("string-ref: not a string", sexp_list1(ctx, _ARG1));
-    else if (! sexp_fixnump(_ARG2))
-      sexp_raise("string-ref: not an integer", sexp_list1(ctx, _ARG2));
-    i = sexp_unbox_fixnum(_ARG2);
-    if ((i < 0) || (i >= sexp_string_length(_ARG1)))
-      sexp_raise("string-ref: index out of range", sexp_list2(ctx, _ARG1, _ARG2));
-    _ARG2 = sexp_string_ref(_ARG1, _ARG2);
-    top--;
-    break;
-  case SEXP_OP_STRING_SET:
-    if (! sexp_stringp(_ARG1))
-      sexp_raise("string-set!: not a string", sexp_list1(ctx, _ARG1));
-    else if (sexp_immutablep(_ARG1))
-      sexp_raise("string-set!: immutable string", sexp_list1(ctx, _ARG1));
-    else if (! sexp_fixnump(_ARG2))
-      sexp_raise("string-set!: not an integer", sexp_list1(ctx, _ARG2));
-    else if (! sexp_charp(_ARG3))
-      sexp_raise("string-set!: not a char", sexp_list1(ctx, _ARG3));
-    i = sexp_unbox_fixnum(_ARG2);
-    if ((i < 0) || (i >= sexp_string_length(_ARG1)))
-      sexp_raise("string-set!: index out of range", sexp_list2(ctx, _ARG1, _ARG2));
-    sexp_string_set(_ARG1, _ARG2, _ARG3);
-    _ARG3 = SEXP_VOID;
-    top-=2;
-    break;
-  case SEXP_OP_STRING_LENGTH:
-    if (! sexp_stringp(_ARG1))
-      sexp_raise("string-length: not a string", sexp_list1(ctx, _ARG1));
-    _ARG1 = sexp_make_fixnum(sexp_string_length(_ARG1));
-    break;
-  case SEXP_OP_MAKE_PROCEDURE:
-    sexp_context_top(ctx) = top;
-    _ARG4 = sexp_make_procedure(ctx, _ARG1, _ARG2, _ARG3, _ARG4);
-    top-=3;
-    break;
-  case SEXP_OP_MAKE_VECTOR:
-    sexp_context_top(ctx) = top;
-    if (! sexp_fixnump(_ARG1))
-      sexp_raise("make-vector: not an integer", sexp_list1(ctx, _ARG1));
-    _ARG2 = sexp_make_vector(ctx, _ARG1, _ARG2);
-    top--;
-    break;
-  case SEXP_OP_MAKE_EXCEPTION:
-    _ARG5 = sexp_make_exception(ctx, _ARG1, _ARG2, _ARG3, _ARG4, _ARG5);
-    top -= 4;
-    break;
-  case SEXP_OP_AND:
-    _ARG2 = sexp_make_boolean((_ARG1 != SEXP_FALSE) && (_ARG2 != SEXP_FALSE));
-    top--;
-    break;
-  case SEXP_OP_EOFP:
-    _ARG1 = sexp_make_boolean(_ARG1 == SEXP_EOF); break;
-  case SEXP_OP_NULLP:
-    _ARG1 = sexp_make_boolean(sexp_nullp(_ARG1)); break;
-  case SEXP_OP_FIXNUMP:
-    _ARG1 = sexp_make_boolean(sexp_fixnump(_ARG1)); break;
-  case SEXP_OP_SYMBOLP:
-    _ARG1 = sexp_make_boolean(sexp_symbolp(_ARG1)); break;
-  case SEXP_OP_CHARP:
-    _ARG1 = sexp_make_boolean(sexp_charp(_ARG1)); break;
-  case SEXP_OP_TYPEP:
-    _ALIGN_IP();
-    _ARG1 = sexp_make_boolean(sexp_check_tag(_ARG1, _UWORD0));
-    ip += sizeof(sexp);
-    break;
-  case SEXP_OP_MAKE:
-    _ALIGN_IP();
-    _PUSH(sexp_alloc_tagged(ctx, _UWORD1, _UWORD0));
-    ip += sizeof(sexp)*2;
-    break;
-  case SEXP_OP_SLOT_REF:
-    _ALIGN_IP();
-    if (! sexp_check_tag(_ARG1, _UWORD0))
-      sexp_raise("slot-ref: bad type", sexp_list2(ctx, sexp_c_string(ctx, sexp_type_name_by_index(ctx, _UWORD0), -1), _ARG1));
-    _ARG1 = sexp_slot_ref(_ARG1, _UWORD1);
-    ip += sizeof(sexp)*2;
-    break;
-  case SEXP_OP_SLOT_SET:
-    _ALIGN_IP();
-    if (! sexp_check_tag(_ARG1, _UWORD0))
-      sexp_raise("slot-set!: bad type", sexp_list2(ctx, sexp_c_string(ctx, sexp_type_name_by_index(ctx, _UWORD0), -1), _ARG1));
-    else if (sexp_immutablep(_ARG1))
-      sexp_raise("slot-set!: immutable object", sexp_list1(ctx, _ARG1));
-    sexp_slot_set(_ARG1, _UWORD1, _ARG2);
-    _ARG2 = SEXP_VOID;
-    ip += sizeof(sexp)*2;
-    top--;
-    break;
-  case SEXP_OP_CAR:
-    if (! sexp_pairp(_ARG1))
-      sexp_raise("car: not a pair", sexp_list1(ctx, _ARG1));
-    _ARG1 = sexp_car(_ARG1); break;
-  case SEXP_OP_CDR:
-    if (! sexp_pairp(_ARG1))
-      sexp_raise("cdr: not a pair", sexp_list1(ctx, _ARG1));
-    _ARG1 = sexp_cdr(_ARG1); break;
-  case SEXP_OP_SET_CAR:
-    if (! sexp_pairp(_ARG1))
-      sexp_raise("set-car!: not a pair", sexp_list1(ctx, _ARG1));
-    else if (sexp_immutablep(_ARG1))
-      sexp_raise("set-car!: immutable pair", sexp_list1(ctx, _ARG1));
-    sexp_car(_ARG1) = _ARG2;
-    _ARG2 = SEXP_VOID;
-    top--;
-    break;
-  case SEXP_OP_SET_CDR:
-    if (! sexp_pairp(_ARG1))
-      sexp_raise("set-cdr!: not a pair", sexp_list1(ctx, _ARG1));
-    else if (sexp_immutablep(_ARG1))
-      sexp_raise("set-cdr!: immutable pair", sexp_list1(ctx, _ARG1));
-    sexp_cdr(_ARG1) = _ARG2;
-    _ARG2 = SEXP_VOID;
-    top--;
-    break;
-  case SEXP_OP_CONS:
-    sexp_context_top(ctx) = top;
-    _ARG2 = sexp_cons(ctx, _ARG1, _ARG2);
-    top--;
-    break;
-  case SEXP_OP_ADD:
-#if SEXP_USE_BIGNUMS
-    tmp1 = _ARG1, tmp2 = _ARG2;
-    sexp_context_top(ctx) = top;
-    if (sexp_fixnump(tmp1) && sexp_fixnump(tmp2)) {
-      j = sexp_unbox_fixnum(tmp1) + sexp_unbox_fixnum(tmp2);
-      if ((j < SEXP_MIN_FIXNUM) || (j > SEXP_MAX_FIXNUM))
-        _ARG2 = sexp_add(ctx, tmp1=sexp_fixnum_to_bignum(ctx, tmp1), tmp2);
-      else
-        _ARG2 = sexp_make_fixnum(j);
-    }
-    else
-      _ARG2 = sexp_add(ctx, tmp1, tmp2);
-#else
-    if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2))
-      _ARG2 = sexp_fx_add(_ARG1, _ARG2);
-#if SEXP_USE_FLONUMS
-    else if (sexp_flonump(_ARG1) && sexp_flonump(_ARG2))
-      _ARG2 = sexp_fp_add(ctx, _ARG1, _ARG2);
-    else if (sexp_flonump(_ARG1) && sexp_fixnump(_ARG2))
-      _ARG2 = sexp_make_flonum(ctx, sexp_flonum_value(_ARG1) + (double)sexp_unbox_fixnum(_ARG2));
-    else if (sexp_fixnump(_ARG1) && sexp_flonump(_ARG2))
-      _ARG2 = sexp_make_flonum(ctx, (double)sexp_unbox_fixnum(_ARG1) + sexp_flonum_value(_ARG2));
-#endif
-    else sexp_raise("+: not a number", sexp_list2(ctx, _ARG1, _ARG2));
-#endif
-    top--;
-    break;
-  case SEXP_OP_SUB:
-#if SEXP_USE_BIGNUMS
-    tmp1 = _ARG1, tmp2 = _ARG2;
-    sexp_context_top(ctx) = top;
-    if (sexp_fixnump(tmp1) && sexp_fixnump(tmp2)) {
-      j = sexp_unbox_fixnum(tmp1) - sexp_unbox_fixnum(tmp2);
-      if ((j < SEXP_MIN_FIXNUM) || (j > SEXP_MAX_FIXNUM))
-        _ARG2 = sexp_sub(ctx, tmp1=sexp_fixnum_to_bignum(ctx, tmp1), tmp2);
-      else
-        _ARG2 = sexp_make_fixnum(j);
-    }
-    else
-      _ARG2 = sexp_sub(ctx, tmp1, tmp2);
-#else
-    if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2))
-      _ARG2 = sexp_fx_sub(_ARG1, _ARG2);
-#if SEXP_USE_FLONUMS
-    else if (sexp_flonump(_ARG1) && sexp_flonump(_ARG2))
-      _ARG2 = sexp_fp_sub(ctx, _ARG1, _ARG2);
-    else if (sexp_flonump(_ARG1) && sexp_fixnump(_ARG2))
-      _ARG2 = sexp_make_flonum(ctx, sexp_flonum_value(_ARG1) - (double)sexp_unbox_fixnum(_ARG2));
-    else if (sexp_fixnump(_ARG1) && sexp_flonump(_ARG2))
-      _ARG2 = sexp_make_flonum(ctx, (double)sexp_unbox_fixnum(_ARG1) - sexp_flonum_value(_ARG2));
-#endif
-    else sexp_raise("-: not a number", sexp_list2(ctx, _ARG1, _ARG2));
-#endif
-    top--;
-    break;
-  case SEXP_OP_MUL:
-#if SEXP_USE_BIGNUMS
-    tmp1 = _ARG1, tmp2 = _ARG2;
-    sexp_context_top(ctx) = top;
-    if (sexp_fixnump(tmp1) && sexp_fixnump(tmp2)) {
-      prod = (sexp_lsint_t)sexp_unbox_fixnum(tmp1) * sexp_unbox_fixnum(tmp2);
-      if ((prod < SEXP_MIN_FIXNUM) || (prod > SEXP_MAX_FIXNUM))
-        _ARG2 = sexp_mul(ctx, tmp1=sexp_fixnum_to_bignum(ctx, tmp1), tmp2);
-      else
-        _ARG2 = sexp_make_fixnum(prod);
-    }
-    else
-      _ARG2 = sexp_mul(ctx, tmp1, tmp2);
-#else
-    if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2))
-      _ARG2 = sexp_fx_mul(_ARG1, _ARG2);
-#if SEXP_USE_FLONUMS
-    else if (sexp_flonump(_ARG1) && sexp_flonump(_ARG2))
-      _ARG2 = sexp_fp_mul(ctx, _ARG1, _ARG2);
-    else if (sexp_flonump(_ARG1) && sexp_fixnump(_ARG2))
-      _ARG2 = sexp_make_flonum(ctx, sexp_flonum_value(_ARG1) * (double)sexp_unbox_fixnum(_ARG2));
-    else if (sexp_fixnump(_ARG1) && sexp_flonump(_ARG2))
-      _ARG2 = sexp_make_flonum(ctx, (double)sexp_unbox_fixnum(_ARG1) * sexp_flonum_value(_ARG2));
-#endif
-    else sexp_raise("*: not a number", sexp_list2(ctx, _ARG1, _ARG2));
-#endif
-    top--;
-    break;
-  case SEXP_OP_DIV:
-    sexp_context_top(ctx) = top;
-    if (_ARG2 == SEXP_ZERO) {
-#if SEXP_USE_FLONUMS
-      if (sexp_flonump(_ARG1) && sexp_flonum_value(_ARG1) == 0.0)
-        _ARG2 = sexp_make_flonum(ctx, 0.0/0.0);
-      else
-#endif
-        sexp_raise("divide by zero", SEXP_NULL);
-    } else if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2)) {
-#if SEXP_USE_FLONUMS
-      _ARG1 = sexp_fixnum_to_flonum(ctx, _ARG1);
-      _ARG2 = sexp_fixnum_to_flonum(ctx, _ARG2);
-      _ARG2 = sexp_fp_div(ctx, _ARG1, _ARG2);
-      if (sexp_flonum_value(_ARG2) == trunc(sexp_flonum_value(_ARG2)))
-        _ARG2 = sexp_make_fixnum(sexp_flonum_value(_ARG2));
-#else
-      _ARG2 = sexp_fx_div(_ARG1, _ARG2);
-#endif
-    }
-#if SEXP_USE_BIGNUMS
-    else
-      _ARG2 = sexp_div(ctx, _ARG1, _ARG2);
-#else
-#if SEXP_USE_FLONUMS
-    else if (sexp_flonump(_ARG1) && sexp_flonump(_ARG2))
-      _ARG2 = sexp_fp_div(ctx, _ARG1, _ARG2);
-    else if (sexp_flonump(_ARG1) && sexp_fixnump(_ARG2))
-      _ARG2 = sexp_make_flonum(ctx, sexp_flonum_value(_ARG1) / (double)sexp_unbox_fixnum(_ARG2));
-    else if (sexp_fixnump(_ARG1) && sexp_flonump(_ARG2))
-      _ARG2 = sexp_make_flonum(ctx, (double)sexp_unbox_fixnum(_ARG1) / sexp_flonum_value(_ARG2));
-#endif
-    else sexp_raise("/: not a number", sexp_list2(ctx, _ARG1, _ARG2));
-#endif
-    top--;
-    break;
-  case SEXP_OP_QUOTIENT:
-    if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2)) {
-      if (_ARG2 == SEXP_ZERO)
-        sexp_raise("divide by zero", SEXP_NULL);
-      _ARG2 = sexp_fx_div(_ARG1, _ARG2);
-      top--;
-    }
-#if SEXP_USE_BIGNUMS
-    else {
-      sexp_context_top(ctx) = top;
-      _ARG2 = sexp_quotient(ctx, _ARG1, _ARG2);
-      top--;
-    }
-#else
-    else sexp_raise("quotient: not an integer", sexp_list2(ctx, _ARG1, _ARG2));
-#endif
-    break;
-  case SEXP_OP_REMAINDER:
-    if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2)) {
-      if (_ARG2 == SEXP_ZERO)
-        sexp_raise("divide by zero", SEXP_NULL);
-      tmp1 = sexp_fx_rem(_ARG1, _ARG2);
-      top--;
-      _ARG1 = tmp1;
-    }
-#if SEXP_USE_BIGNUMS
-    else {
-      sexp_context_top(ctx) = top;
-      _ARG2 = sexp_remainder(ctx, _ARG1, _ARG2);
-      top--;
-    }
-#else
-    else sexp_raise("remainder: not an integer", sexp_list2(ctx, _ARG1, _ARG2));
-#endif
-    break;
-  case SEXP_OP_LT:
-    if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2)) {
-      i = (sexp_sint_t)_ARG1 < (sexp_sint_t)_ARG2;
-#if SEXP_USE_BIGNUMS
-      _ARG2 = sexp_make_boolean(i);
-    } else {
-      tmp1 = sexp_compare(ctx, _ARG1, _ARG2);
-      _ARG2 = sexp_fixnump(tmp1)
-        ? sexp_make_boolean(sexp_unbox_fixnum(tmp1) < 0) : tmp1;
-    }
-#else
-#if SEXP_USE_FLONUMS
-    } else if (sexp_flonump(_ARG1) && sexp_flonump(_ARG2)) {
-      i = sexp_flonum_value(_ARG1) < sexp_flonum_value(_ARG2);
-    } else if (sexp_flonump(_ARG1) && sexp_fixnump(_ARG2)) {
-      i = sexp_flonum_value(_ARG1) < (double)sexp_unbox_fixnum(_ARG2); 
-    } else if (sexp_fixnump(_ARG1) && sexp_flonump(_ARG2)) {
-      i = (double)sexp_unbox_fixnum(_ARG1) < sexp_flonum_value(_ARG2);
-#endif
-    } else sexp_raise("<: not a number", sexp_list2(ctx, _ARG1, _ARG2));
-    _ARG2 = sexp_make_boolean(i);
-#endif
-    top--;
-    break;
-  case SEXP_OP_LE:
-    if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2)) {
-      i = (sexp_sint_t)_ARG1 <= (sexp_sint_t)_ARG2;
-#if SEXP_USE_BIGNUMS
-      _ARG2 = sexp_make_boolean(i);
-    } else {
-      tmp1 = sexp_compare(ctx, _ARG1, _ARG2);
-      _ARG2 = sexp_fixnump(tmp1)
-        ? sexp_make_boolean(sexp_unbox_fixnum(tmp1) <= 0) : tmp1;
-    }
-#else
-#if SEXP_USE_FLONUMS
-    } else if (sexp_flonump(_ARG1) && sexp_flonump(_ARG2)) {
-      i = sexp_flonum_value(_ARG1) <= sexp_flonum_value(_ARG2);
-    } else if (sexp_flonump(_ARG1) && sexp_fixnump(_ARG2)) {
-      i = sexp_flonum_value(_ARG1) <= (double)sexp_unbox_fixnum(_ARG2);
-    } else if (sexp_fixnump(_ARG1) && sexp_flonump(_ARG2)) {
-      i = (double)sexp_unbox_fixnum(_ARG1) <= sexp_flonum_value(_ARG2);
-#endif
-    } else sexp_raise("<=: not a number", sexp_list2(ctx, _ARG1, _ARG2));
-    _ARG2 = sexp_make_boolean(i);
-#endif
-    top--;
-    break;
-  case SEXP_OP_EQN:
-    if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2)) {
-      i = _ARG1 == _ARG2;
-#if SEXP_USE_BIGNUMS
-      _ARG2 = sexp_make_boolean(i);
-    } else {
-      tmp1 = sexp_compare(ctx, _ARG1, _ARG2);
-      _ARG2 = sexp_fixnump(tmp1)
-        ? sexp_make_boolean(sexp_unbox_fixnum(tmp1) == 0) : tmp1;
-    }
-#else
-#if SEXP_USE_FLONUMS
-    } else if (sexp_flonump(_ARG1) && sexp_flonump(_ARG2)) {
-      i = sexp_flonum_value(_ARG1) == sexp_flonum_value(_ARG2);
-    } else if (sexp_flonump(_ARG1) && sexp_fixnump(_ARG2)) {
-      i = sexp_flonum_value(_ARG1) == (double)sexp_unbox_fixnum(_ARG2);
-    } else if (sexp_fixnump(_ARG1) && sexp_flonump(_ARG2)) {
-      i = (double)sexp_unbox_fixnum(_ARG1) == sexp_flonum_value(_ARG2);
-#endif
-    } else sexp_raise("=: not a number", sexp_list2(ctx, _ARG1, _ARG2));
-    _ARG2 = sexp_make_boolean(i);
-#endif
-    top--;
-    break;
-  case SEXP_OP_EQ:
-    _ARG2 = sexp_make_boolean(_ARG1 == _ARG2);
-    top--;
-    break;
-  case SEXP_OP_FIX2FLO:
-    if (sexp_fixnump(_ARG1))
-      _ARG1 = sexp_fixnum_to_flonum(ctx, _ARG1);
-#if SEXP_USE_BIGNUMS
-    else if (sexp_bignump(_ARG1))
-      _ARG1 = sexp_make_flonum(ctx, sexp_bignum_to_double(_ARG1));
-#endif
-    else if (! sexp_flonump(_ARG1))
-      sexp_raise("exact->inexact: not a number", sexp_list1(ctx, _ARG1));
-    break;
-  case SEXP_OP_FLO2FIX:
-    if (sexp_flonump(_ARG1)) {
-      if (sexp_flonum_value(_ARG1) != trunc(sexp_flonum_value(_ARG1))) {
-        sexp_raise("inexact->exact: not an integer", sexp_list1(ctx, _ARG1));
-#if SEXP_USE_BIGNUMS
-      } else if ((sexp_flonum_value(_ARG1) > SEXP_MAX_FIXNUM)
-                 || sexp_flonum_value(_ARG1) < SEXP_MIN_FIXNUM) {
-        _ARG1 = sexp_double_to_bignum(ctx, sexp_flonum_value(_ARG1));
-#endif
-      } else {
-        _ARG1 = sexp_make_fixnum((sexp_sint_t)sexp_flonum_value(_ARG1));
-      }
-    } else if (! sexp_fixnump(_ARG1) && ! sexp_bignump(_ARG1)) {
-      sexp_raise("inexact->exact: not a number", sexp_list1(ctx, _ARG1));
-    }
-    break;
-  case SEXP_OP_CHAR2INT:
-    if (! sexp_charp(_ARG1))
-      sexp_raise("char->integer: not a character", sexp_list1(ctx, _ARG1));
-    _ARG1 = sexp_make_fixnum(sexp_unbox_character(_ARG1));
-    break;
-  case SEXP_OP_INT2CHAR:
-    if (! sexp_fixnump(_ARG1))
-      sexp_raise("integer->char: not an integer", sexp_list1(ctx, _ARG1));
-    _ARG1 = sexp_make_character(sexp_unbox_fixnum(_ARG1));
-    break;
-  case SEXP_OP_CHAR_UPCASE:
-    if (! sexp_charp(_ARG1))
-      sexp_raise("char-upcase: not a character", sexp_list1(ctx, _ARG1));
-    _ARG1 = sexp_make_character(toupper(sexp_unbox_character(_ARG1)));
-    break;
-  case SEXP_OP_CHAR_DOWNCASE:
-    if (! sexp_charp(_ARG1))
-      sexp_raise("char-downcase: not a character", sexp_list1(ctx, _ARG1));
-    _ARG1 = sexp_make_character(tolower(sexp_unbox_character(_ARG1)));
-    break;
-  case SEXP_OP_WRITE_CHAR:
-    if (! sexp_charp(_ARG1))
-      sexp_raise("write-char: not a character", sexp_list1(ctx, _ARG1));
-    if (! sexp_oportp(_ARG2))
-      sexp_raise("write-char: not an output-port", sexp_list1(ctx, _ARG2));
-    sexp_write_char(ctx, sexp_unbox_character(_ARG1), _ARG2);
-    _ARG2 = SEXP_VOID;
-    top--;
-    break;
-  case SEXP_OP_NEWLINE:
-    if (! sexp_oportp(_ARG1))
-      sexp_raise("newline: not an output-port", sexp_list1(ctx, _ARG1));
-    sexp_newline(ctx, _ARG1);
-    _ARG1 = SEXP_VOID;
-    break;
-  case SEXP_OP_READ_CHAR:
-    if (! sexp_iportp(_ARG1))
-      sexp_raise("read-char: not an intput-port", sexp_list1(ctx, _ARG1));
-    i = sexp_read_char(ctx, _ARG1);
-    _ARG1 = (i == EOF) ? SEXP_EOF : sexp_make_character(i);
-    break;
-  case SEXP_OP_PEEK_CHAR:
-    if (! sexp_iportp(_ARG1))
-      sexp_raise("peek-char: not an intput-port", sexp_list1(ctx, _ARG1));
-    i = sexp_read_char(ctx, _ARG1);
-    sexp_push_char(ctx, i, _ARG1);
-    _ARG1 = (i == EOF) ? SEXP_EOF : sexp_make_character(i);
-    break;
-  case SEXP_OP_RET:
-    i = sexp_unbox_fixnum(stack[fp]);
-    stack[fp-i] = _ARG1;
-    top = fp-i+1;
-    self = stack[fp+2];
-    bc = sexp_procedure_code(self);
-    ip = sexp_bytecode_data(bc) + sexp_unbox_fixnum(stack[fp+1]);
-    cp = sexp_procedure_vars(self);
-    fp = sexp_unbox_fixnum(stack[fp+3]);
-    break;
-  case SEXP_OP_DONE:
-    goto end_loop;
-  default:
-    sexp_raise("unknown opcode", sexp_list1(ctx, sexp_make_fixnum(*(ip-1))));
-  }
-  goto loop;
-
- end_loop:
-  sexp_gc_release3(ctx);
-  sexp_context_top(ctx) = top;
-  return _ARG1;
-}
+#include "vm.c"
 
 /************************ library procedures **************************/
 
diff --git a/vm.c b/vm.c
new file mode 100644
index 00000000..e0edd053
--- /dev/null
+++ b/vm.c
@@ -0,0 +1,797 @@
+/*  vm.c -- stack-based virtual machine backend               */
+/*  Copyright (c) 2009-2010 Alex Shinn.  All rights reserved. */
+/*  BSD-style license: http://synthcode.com/license.txt       */
+
+/*********************** the virtual machine **************************/
+
+static sexp sexp_save_stack (sexp ctx, sexp *stack, sexp_uint_t to) {
+  sexp res, *data;
+  sexp_uint_t i;
+  res = sexp_make_vector(ctx, sexp_make_fixnum(to), SEXP_VOID);
+  data = sexp_vector_data(res);
+  for (i=0; i<to; i++)
+    data[i] = stack[i];
+  return res;
+}
+
+static sexp_uint_t sexp_restore_stack (sexp saved, sexp *current) {
+  sexp_uint_t len = sexp_vector_length(saved), i;
+  sexp *from = sexp_vector_data(saved);
+  for (i=0; i<len; i++)
+    current[i] = from[i];
+  return len;
+}
+
+#define _ARG1 stack[top-1]
+#define _ARG2 stack[top-2]
+#define _ARG3 stack[top-3]
+#define _ARG4 stack[top-4]
+#define _ARG5 stack[top-5]
+#define _ARG6 stack[top-6]
+#define _PUSH(x) (stack[top++]=(x))
+
+#if SEXP_USE_ALIGNED_BYTECODE
+#define _ALIGN_IP() ip = (unsigned char *)sexp_word_align((unsigned long)ip)
+#else
+#define _ALIGN_IP()
+#endif
+
+#define _WORD0 ((sexp*)ip)[0]
+#define _UWORD0 ((sexp_uint_t*)ip)[0]
+#define _SWORD0 ((sexp_sint_t*)ip)[0]
+#define _WORD1 ((sexp*)ip)[1]
+#define _UWORD1 ((sexp_uint_t*)ip)[1]
+#define _SWORD1 ((sexp_sint_t*)ip)[1]
+
+#define sexp_raise(msg, args)                                       \
+  do {sexp_context_top(ctx) = top+1;                                \
+      stack[top] = args;                                            \
+      stack[top] = sexp_user_exception(ctx, self, msg, stack[top]); \
+      top++;                                                        \
+      goto call_error_handler;}                                     \
+  while (0)
+
+#define sexp_check_exception() do {if (sexp_exceptionp(_ARG1)) \
+                                     goto call_error_handler;} \
+                                while (0)
+
+sexp sexp_vm (sexp ctx, sexp proc) {
+  sexp bc = sexp_procedure_code(proc), cp = sexp_procedure_vars(proc);
+  sexp *stack = sexp_stack_data(sexp_context_stack(ctx));
+  unsigned char *ip = sexp_bytecode_data(bc);
+  sexp_sint_t i, j, k, fp, top = sexp_stack_top(sexp_context_stack(ctx));
+#if SEXP_USE_BIGNUMS
+  sexp_lsint_t prod;
+#endif
+  sexp_gc_var3(self, tmp1, tmp2);
+  sexp_gc_preserve3(ctx, self, tmp1, tmp2);
+  fp = top - 4;
+  self = proc;
+
+ loop:
+#if SEXP_USE_DEBUG_VM
+  if (sexp_context_tracep(ctx)) {
+    sexp_print_stack(ctx, stack, top, fp, SEXP_FALSE);
+    fprintf(stderr, "%s\n", (*ip<=SEXP_OP_NUM_OPCODES) ?
+            reverse_opcode_names[*ip] : "UNKNOWN");
+  }
+#endif
+  switch (*ip++) {
+  case SEXP_OP_NOOP:
+    break;
+  case SEXP_OP_RAISE:
+  call_error_handler:
+    tmp1 = sexp_cdr(sexp_global(ctx, SEXP_G_ERR_HANDLER));
+    if (! sexp_procedurep(tmp1)) goto end_loop;
+    stack[top] = (sexp) 1;
+    stack[top+1] = sexp_make_fixnum(ip-sexp_bytecode_data(bc));
+    stack[top+2] = self;
+    stack[top+3] = sexp_make_fixnum(fp);
+    top += 4;
+    self = tmp1;
+    bc = sexp_procedure_code(self);
+    ip = sexp_bytecode_data(bc);
+    cp = sexp_procedure_vars(self);
+    fp = top-4;
+    break;
+  case SEXP_OP_RESUMECC:
+    tmp1 = stack[fp-1];
+    top = sexp_restore_stack(sexp_vector_ref(cp, 0), stack);
+    fp = sexp_unbox_fixnum(_ARG1);
+    self = _ARG2;
+    bc = sexp_procedure_code(self);
+    cp = sexp_procedure_vars(self);
+    ip = sexp_bytecode_data(bc) + sexp_unbox_fixnum(_ARG3);
+    i = sexp_unbox_fixnum(_ARG4);
+    top -= 4;
+    _ARG1 = tmp1;
+    break;
+  case SEXP_OP_CALLCC:
+    stack[top] = SEXP_ONE;
+    stack[top+1] = sexp_make_fixnum(ip-sexp_bytecode_data(bc));
+    stack[top+2] = self;
+    stack[top+3] = sexp_make_fixnum(fp);
+    tmp1 = _ARG1;
+    i = 1;
+    sexp_context_top(ctx) = top;
+    tmp2 = sexp_make_vector(ctx, SEXP_ONE, SEXP_UNDEF);
+    sexp_vector_set(tmp2, SEXP_ZERO, sexp_save_stack(ctx, stack, top+4));
+    _ARG1 = sexp_make_procedure(ctx,
+                                SEXP_ZERO,
+                                SEXP_ONE,
+                                sexp_global(ctx, SEXP_G_RESUMECC_BYTECODE),
+                                tmp2);
+    top++;
+    ip -= sizeof(sexp);
+    goto make_call;
+  case SEXP_OP_APPLY1:
+    tmp1 = _ARG1;
+    tmp2 = _ARG2;
+    i = sexp_unbox_fixnum(sexp_length(ctx, tmp2));
+    top += (i-2);
+    for ( ; sexp_pairp(tmp2); tmp2=sexp_cdr(tmp2), top--)
+      _ARG1 = sexp_car(tmp2);
+    top += i+1;
+    ip -= sizeof(sexp);
+    goto make_call;
+  case SEXP_OP_TAIL_CALL:
+    _ALIGN_IP();
+    i = sexp_unbox_fixnum(_WORD0);    /* number of params */
+    tmp1 = _ARG1;                              /* procedure to call */
+    /* save frame info */
+    tmp2 = stack[fp+3];
+    j = sexp_unbox_fixnum(stack[fp]);
+    self = stack[fp+2];
+    bc = sexp_procedure_vars(self);
+    cp = sexp_procedure_vars(self);
+    ip = (sexp_bytecode_data(bc)
+          + sexp_unbox_fixnum(stack[fp+1])) - sizeof(sexp);
+    /* copy new args into place */
+    for (k=0; k<i; k++)
+      stack[fp-j+k] = stack[top-1-i+k];
+    top = fp+i-j+1;
+    fp = sexp_unbox_fixnum(tmp2);
+    goto make_call;
+  case SEXP_OP_CALL:
+#if SEXP_USE_CHECK_STACK
+    if (top+16 >= SEXP_INIT_STACK_SIZE) {
+      _ARG1 = sexp_global(ctx, SEXP_G_OOS_ERROR);
+      goto end_loop;
+    }
+#endif
+    _ALIGN_IP();
+    i = sexp_unbox_fixnum(_WORD0);
+    tmp1 = _ARG1;
+  make_call:
+    if (sexp_opcodep(tmp1)) {
+      /* compile non-inlined opcode applications on the fly */
+      sexp_context_top(ctx) = top;
+      tmp1 = make_opcode_procedure(ctx, tmp1, i);
+      if (sexp_exceptionp(tmp1)) {
+        _ARG1 = tmp1;
+        goto call_error_handler;
+      }
+    }
+    if (! sexp_procedurep(tmp1))
+      sexp_raise("non procedure application", sexp_list1(ctx, tmp1));
+    j = i - sexp_unbox_fixnum(sexp_procedure_num_args(tmp1));
+    if (j < 0)
+      sexp_raise("not enough args",
+                 sexp_list2(ctx, tmp1, sexp_make_fixnum(i)));
+    if (j > 0) {
+      if (sexp_procedure_variadic_p(tmp1)) {
+        stack[top-i-1] = sexp_cons(ctx, stack[top-i-1], SEXP_NULL);
+        for (k=top-i; k<top-(i-j)-1; k++)
+          stack[top-i-1] = sexp_cons(ctx, stack[k], stack[top-i-1]);
+        for ( ; k<top; k++)
+          stack[k-j+1] = stack[k];
+        top -= (j-1);
+        i -= (j-1);
+      } else {
+        sexp_raise("too many args",
+                   sexp_list2(ctx, tmp1, sexp_make_fixnum(i)));
+      }
+    } else if (sexp_procedure_variadic_p(tmp1)) {
+      /* shift stack, set extra arg to null */
+      for (k=top; k>=top-i; k--)
+        stack[k] = stack[k-1];
+      stack[top-i-1] = SEXP_NULL;
+      top++;
+      i++;
+    }
+    _ARG1 = sexp_make_fixnum(i);
+    stack[top] = sexp_make_fixnum(ip+sizeof(sexp)-sexp_bytecode_data(bc));
+    stack[top+1] = self;
+    stack[top+2] = sexp_make_fixnum(fp);
+    top += 3;
+    self = tmp1;
+    bc = sexp_procedure_code(self);
+    ip = sexp_bytecode_data(bc);
+    cp = sexp_procedure_vars(self);
+    fp = top-4;
+    break;
+  case SEXP_OP_FCALL0:
+    _ALIGN_IP();
+    sexp_context_top(ctx) = top;
+    _PUSH(((sexp_proc1)sexp_opcode_func(_WORD0))(ctx sexp_api_pass(_WORD0, 0)));
+    ip += sizeof(sexp);
+    sexp_check_exception();
+    break;
+  case SEXP_OP_FCALL1:
+    _ALIGN_IP();
+    sexp_context_top(ctx) = top;
+    _ARG1 = ((sexp_proc2)sexp_opcode_func(_WORD0))(ctx sexp_api_pass(_WORD0, 1), _ARG1);
+    ip += sizeof(sexp);
+    sexp_check_exception();
+    break;
+  case SEXP_OP_FCALL2:
+    _ALIGN_IP();
+    sexp_context_top(ctx) = top;
+    _ARG2 = ((sexp_proc3)sexp_opcode_func(_WORD0))(ctx sexp_api_pass(_WORD0, 2), _ARG1, _ARG2);
+    top--;
+    ip += sizeof(sexp);
+    sexp_check_exception();
+    break;
+  case SEXP_OP_FCALL3:
+    _ALIGN_IP();
+    sexp_context_top(ctx) = top;
+    _ARG3 = ((sexp_proc4)sexp_opcode_func(_WORD0))(ctx sexp_api_pass(_WORD0, 3), _ARG1, _ARG2, _ARG3);
+    top -= 2;
+    ip += sizeof(sexp);
+    sexp_check_exception();
+    break;
+  case SEXP_OP_FCALL4:
+    _ALIGN_IP();
+    sexp_context_top(ctx) = top;
+    _ARG4 = ((sexp_proc5)sexp_opcode_func(_WORD0))(ctx sexp_api_pass(_WORD0, 4), _ARG1, _ARG2, _ARG3, _ARG4);
+    top -= 3;
+    ip += sizeof(sexp);
+    sexp_check_exception();
+    break;
+  case SEXP_OP_FCALL5:
+    _ALIGN_IP();
+    sexp_context_top(ctx) = top;
+    _ARG5 = ((sexp_proc6)sexp_opcode_func(_WORD0))(ctx sexp_api_pass(_WORD0, 5), _ARG1, _ARG2, _ARG3, _ARG4, _ARG5);
+    top -= 4;
+    ip += sizeof(sexp);
+    sexp_check_exception();
+    break;
+  case SEXP_OP_FCALL6:
+    _ALIGN_IP();
+    sexp_context_top(ctx) = top;
+    _ARG6 = ((sexp_proc7)sexp_opcode_func(_WORD0))(ctx sexp_api_pass(_WORD0, 6), _ARG1, _ARG2, _ARG3, _ARG4, _ARG5, _ARG6);
+    top -= 5;
+    ip += sizeof(sexp);
+    sexp_check_exception();
+    break;
+  case SEXP_OP_JUMP_UNLESS:
+    _ALIGN_IP();
+    if (stack[--top] == SEXP_FALSE)
+      ip += _SWORD0;
+    else
+      ip += sizeof(sexp_sint_t);
+    break;
+  case SEXP_OP_JUMP:
+    _ALIGN_IP();
+    ip += _SWORD0;
+    break;
+  case SEXP_OP_PUSH:
+    _ALIGN_IP();
+    _PUSH(_WORD0);
+    ip += sizeof(sexp);
+    break;
+  case SEXP_OP_DROP:
+    top--;
+    break;
+  case SEXP_OP_GLOBAL_REF:
+    _ALIGN_IP();
+    if (sexp_cdr(_WORD0) == SEXP_UNDEF)
+      sexp_raise("undefined variable", sexp_list1(ctx, sexp_car(_WORD0)));
+    /* ... FALLTHROUGH ... */
+  case SEXP_OP_GLOBAL_KNOWN_REF:
+    _ALIGN_IP();
+    _PUSH(sexp_cdr(_WORD0));
+    ip += sizeof(sexp);
+    break;
+  case SEXP_OP_STACK_REF:            /* `pick' in forth */
+    _ALIGN_IP();
+    stack[top] = stack[top - _SWORD0];
+    ip += sizeof(sexp);
+    top++;
+    break;
+  case SEXP_OP_LOCAL_REF:
+    _ALIGN_IP();
+    stack[top] = stack[fp - 1 - _SWORD0];
+    ip += sizeof(sexp);
+    top++;
+    break;
+  case SEXP_OP_LOCAL_SET:
+    _ALIGN_IP();
+    stack[fp - 1 - _SWORD0] = _ARG1;
+    _ARG1 = SEXP_VOID;
+    ip += sizeof(sexp);
+    break;
+  case SEXP_OP_CLOSURE_REF:
+    _ALIGN_IP();
+    _PUSH(sexp_vector_ref(cp, sexp_make_fixnum(_WORD0)));
+    ip += sizeof(sexp);
+    break;
+  case SEXP_OP_VECTOR_REF:
+    if (! sexp_vectorp(_ARG1))
+      sexp_raise("vector-ref: not a vector", sexp_list1(ctx, _ARG1));
+    else if (! sexp_fixnump(_ARG2))
+      sexp_raise("vector-ref: not an integer", sexp_list1(ctx, _ARG2));
+    i = sexp_unbox_fixnum(_ARG2);
+    if ((i < 0) || (i >= sexp_vector_length(_ARG1)))
+      sexp_raise("vector-ref: index out of range", sexp_list2(ctx, _ARG1, _ARG2));
+    _ARG2 = sexp_vector_ref(_ARG1, _ARG2);
+    top--;
+    break;
+  case SEXP_OP_VECTOR_SET:
+    if (! sexp_vectorp(_ARG1))
+      sexp_raise("vector-set!: not a vector", sexp_list1(ctx, _ARG1));
+    else if (sexp_immutablep(_ARG1))
+      sexp_raise("vector-set!: immutable vector", sexp_list1(ctx, _ARG1));
+    else if (! sexp_fixnump(_ARG2))
+      sexp_raise("vector-set!: not an integer", sexp_list1(ctx, _ARG2));
+    i = sexp_unbox_fixnum(_ARG2);
+    if ((i < 0) || (i >= sexp_vector_length(_ARG1)))
+      sexp_raise("vector-set!: index out of range", sexp_list2(ctx, _ARG1, _ARG2));
+    sexp_vector_set(_ARG1, _ARG2, _ARG3);
+    _ARG3 = SEXP_VOID;
+    top-=2;
+    break;
+  case SEXP_OP_VECTOR_LENGTH:
+    if (! sexp_vectorp(_ARG1))
+      sexp_raise("vector-length: not a vector", sexp_list1(ctx, _ARG1));
+    _ARG1 = sexp_make_fixnum(sexp_vector_length(_ARG1));
+    break;
+  case SEXP_OP_STRING_REF:
+    if (! sexp_stringp(_ARG1))
+      sexp_raise("string-ref: not a string", sexp_list1(ctx, _ARG1));
+    else if (! sexp_fixnump(_ARG2))
+      sexp_raise("string-ref: not an integer", sexp_list1(ctx, _ARG2));
+    i = sexp_unbox_fixnum(_ARG2);
+    if ((i < 0) || (i >= sexp_string_length(_ARG1)))
+      sexp_raise("string-ref: index out of range", sexp_list2(ctx, _ARG1, _ARG2));
+    _ARG2 = sexp_string_ref(_ARG1, _ARG2);
+    top--;
+    break;
+  case SEXP_OP_STRING_SET:
+    if (! sexp_stringp(_ARG1))
+      sexp_raise("string-set!: not a string", sexp_list1(ctx, _ARG1));
+    else if (sexp_immutablep(_ARG1))
+      sexp_raise("string-set!: immutable string", sexp_list1(ctx, _ARG1));
+    else if (! sexp_fixnump(_ARG2))
+      sexp_raise("string-set!: not an integer", sexp_list1(ctx, _ARG2));
+    else if (! sexp_charp(_ARG3))
+      sexp_raise("string-set!: not a char", sexp_list1(ctx, _ARG3));
+    i = sexp_unbox_fixnum(_ARG2);
+    if ((i < 0) || (i >= sexp_string_length(_ARG1)))
+      sexp_raise("string-set!: index out of range", sexp_list2(ctx, _ARG1, _ARG2));
+    sexp_string_set(_ARG1, _ARG2, _ARG3);
+    _ARG3 = SEXP_VOID;
+    top-=2;
+    break;
+  case SEXP_OP_STRING_LENGTH:
+    if (! sexp_stringp(_ARG1))
+      sexp_raise("string-length: not a string", sexp_list1(ctx, _ARG1));
+    _ARG1 = sexp_make_fixnum(sexp_string_length(_ARG1));
+    break;
+  case SEXP_OP_MAKE_PROCEDURE:
+    sexp_context_top(ctx) = top;
+    _ARG4 = sexp_make_procedure(ctx, _ARG1, _ARG2, _ARG3, _ARG4);
+    top-=3;
+    break;
+  case SEXP_OP_MAKE_VECTOR:
+    sexp_context_top(ctx) = top;
+    if (! sexp_fixnump(_ARG1))
+      sexp_raise("make-vector: not an integer", sexp_list1(ctx, _ARG1));
+    _ARG2 = sexp_make_vector(ctx, _ARG1, _ARG2);
+    top--;
+    break;
+  case SEXP_OP_MAKE_EXCEPTION:
+    _ARG5 = sexp_make_exception(ctx, _ARG1, _ARG2, _ARG3, _ARG4, _ARG5);
+    top -= 4;
+    break;
+  case SEXP_OP_AND:
+    _ARG2 = sexp_make_boolean((_ARG1 != SEXP_FALSE) && (_ARG2 != SEXP_FALSE));
+    top--;
+    break;
+  case SEXP_OP_EOFP:
+    _ARG1 = sexp_make_boolean(_ARG1 == SEXP_EOF); break;
+  case SEXP_OP_NULLP:
+    _ARG1 = sexp_make_boolean(sexp_nullp(_ARG1)); break;
+  case SEXP_OP_FIXNUMP:
+    _ARG1 = sexp_make_boolean(sexp_fixnump(_ARG1)); break;
+  case SEXP_OP_SYMBOLP:
+    _ARG1 = sexp_make_boolean(sexp_symbolp(_ARG1)); break;
+  case SEXP_OP_CHARP:
+    _ARG1 = sexp_make_boolean(sexp_charp(_ARG1)); break;
+  case SEXP_OP_TYPEP:
+    _ALIGN_IP();
+    _ARG1 = sexp_make_boolean(sexp_check_tag(_ARG1, _UWORD0));
+    ip += sizeof(sexp);
+    break;
+  case SEXP_OP_MAKE:
+    _ALIGN_IP();
+    _PUSH(sexp_alloc_tagged(ctx, _UWORD1, _UWORD0));
+    ip += sizeof(sexp)*2;
+    break;
+  case SEXP_OP_SLOT_REF:
+    _ALIGN_IP();
+    if (! sexp_check_tag(_ARG1, _UWORD0))
+      sexp_raise("slot-ref: bad type", sexp_list2(ctx, sexp_c_string(ctx, sexp_type_name_by_index(ctx, _UWORD0), -1), _ARG1));
+    _ARG1 = sexp_slot_ref(_ARG1, _UWORD1);
+    ip += sizeof(sexp)*2;
+    break;
+  case SEXP_OP_SLOT_SET:
+    _ALIGN_IP();
+    if (! sexp_check_tag(_ARG1, _UWORD0))
+      sexp_raise("slot-set!: bad type", sexp_list2(ctx, sexp_c_string(ctx, sexp_type_name_by_index(ctx, _UWORD0), -1), _ARG1));
+    else if (sexp_immutablep(_ARG1))
+      sexp_raise("slot-set!: immutable object", sexp_list1(ctx, _ARG1));
+    sexp_slot_set(_ARG1, _UWORD1, _ARG2);
+    _ARG2 = SEXP_VOID;
+    ip += sizeof(sexp)*2;
+    top--;
+    break;
+  case SEXP_OP_CAR:
+    if (! sexp_pairp(_ARG1))
+      sexp_raise("car: not a pair", sexp_list1(ctx, _ARG1));
+    _ARG1 = sexp_car(_ARG1); break;
+  case SEXP_OP_CDR:
+    if (! sexp_pairp(_ARG1))
+      sexp_raise("cdr: not a pair", sexp_list1(ctx, _ARG1));
+    _ARG1 = sexp_cdr(_ARG1); break;
+  case SEXP_OP_SET_CAR:
+    if (! sexp_pairp(_ARG1))
+      sexp_raise("set-car!: not a pair", sexp_list1(ctx, _ARG1));
+    else if (sexp_immutablep(_ARG1))
+      sexp_raise("set-car!: immutable pair", sexp_list1(ctx, _ARG1));
+    sexp_car(_ARG1) = _ARG2;
+    _ARG2 = SEXP_VOID;
+    top--;
+    break;
+  case SEXP_OP_SET_CDR:
+    if (! sexp_pairp(_ARG1))
+      sexp_raise("set-cdr!: not a pair", sexp_list1(ctx, _ARG1));
+    else if (sexp_immutablep(_ARG1))
+      sexp_raise("set-cdr!: immutable pair", sexp_list1(ctx, _ARG1));
+    sexp_cdr(_ARG1) = _ARG2;
+    _ARG2 = SEXP_VOID;
+    top--;
+    break;
+  case SEXP_OP_CONS:
+    sexp_context_top(ctx) = top;
+    _ARG2 = sexp_cons(ctx, _ARG1, _ARG2);
+    top--;
+    break;
+  case SEXP_OP_ADD:
+#if SEXP_USE_BIGNUMS
+    tmp1 = _ARG1, tmp2 = _ARG2;
+    sexp_context_top(ctx) = top;
+    if (sexp_fixnump(tmp1) && sexp_fixnump(tmp2)) {
+      j = sexp_unbox_fixnum(tmp1) + sexp_unbox_fixnum(tmp2);
+      if ((j < SEXP_MIN_FIXNUM) || (j > SEXP_MAX_FIXNUM))
+        _ARG2 = sexp_add(ctx, tmp1=sexp_fixnum_to_bignum(ctx, tmp1), tmp2);
+      else
+        _ARG2 = sexp_make_fixnum(j);
+    }
+    else
+      _ARG2 = sexp_add(ctx, tmp1, tmp2);
+#else
+    if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2))
+      _ARG2 = sexp_fx_add(_ARG1, _ARG2);
+#if SEXP_USE_FLONUMS
+    else if (sexp_flonump(_ARG1) && sexp_flonump(_ARG2))
+      _ARG2 = sexp_fp_add(ctx, _ARG1, _ARG2);
+    else if (sexp_flonump(_ARG1) && sexp_fixnump(_ARG2))
+      _ARG2 = sexp_make_flonum(ctx, sexp_flonum_value(_ARG1) + (double)sexp_unbox_fixnum(_ARG2));
+    else if (sexp_fixnump(_ARG1) && sexp_flonump(_ARG2))
+      _ARG2 = sexp_make_flonum(ctx, (double)sexp_unbox_fixnum(_ARG1) + sexp_flonum_value(_ARG2));
+#endif
+    else sexp_raise("+: not a number", sexp_list2(ctx, _ARG1, _ARG2));
+#endif
+    top--;
+    break;
+  case SEXP_OP_SUB:
+#if SEXP_USE_BIGNUMS
+    tmp1 = _ARG1, tmp2 = _ARG2;
+    sexp_context_top(ctx) = top;
+    if (sexp_fixnump(tmp1) && sexp_fixnump(tmp2)) {
+      j = sexp_unbox_fixnum(tmp1) - sexp_unbox_fixnum(tmp2);
+      if ((j < SEXP_MIN_FIXNUM) || (j > SEXP_MAX_FIXNUM))
+        _ARG2 = sexp_sub(ctx, tmp1=sexp_fixnum_to_bignum(ctx, tmp1), tmp2);
+      else
+        _ARG2 = sexp_make_fixnum(j);
+    }
+    else
+      _ARG2 = sexp_sub(ctx, tmp1, tmp2);
+#else
+    if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2))
+      _ARG2 = sexp_fx_sub(_ARG1, _ARG2);
+#if SEXP_USE_FLONUMS
+    else if (sexp_flonump(_ARG1) && sexp_flonump(_ARG2))
+      _ARG2 = sexp_fp_sub(ctx, _ARG1, _ARG2);
+    else if (sexp_flonump(_ARG1) && sexp_fixnump(_ARG2))
+      _ARG2 = sexp_make_flonum(ctx, sexp_flonum_value(_ARG1) - (double)sexp_unbox_fixnum(_ARG2));
+    else if (sexp_fixnump(_ARG1) && sexp_flonump(_ARG2))
+      _ARG2 = sexp_make_flonum(ctx, (double)sexp_unbox_fixnum(_ARG1) - sexp_flonum_value(_ARG2));
+#endif
+    else sexp_raise("-: not a number", sexp_list2(ctx, _ARG1, _ARG2));
+#endif
+    top--;
+    break;
+  case SEXP_OP_MUL:
+#if SEXP_USE_BIGNUMS
+    tmp1 = _ARG1, tmp2 = _ARG2;
+    sexp_context_top(ctx) = top;
+    if (sexp_fixnump(tmp1) && sexp_fixnump(tmp2)) {
+      prod = (sexp_lsint_t)sexp_unbox_fixnum(tmp1) * sexp_unbox_fixnum(tmp2);
+      if ((prod < SEXP_MIN_FIXNUM) || (prod > SEXP_MAX_FIXNUM))
+        _ARG2 = sexp_mul(ctx, tmp1=sexp_fixnum_to_bignum(ctx, tmp1), tmp2);
+      else
+        _ARG2 = sexp_make_fixnum(prod);
+    }
+    else
+      _ARG2 = sexp_mul(ctx, tmp1, tmp2);
+#else
+    if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2))
+      _ARG2 = sexp_fx_mul(_ARG1, _ARG2);
+#if SEXP_USE_FLONUMS
+    else if (sexp_flonump(_ARG1) && sexp_flonump(_ARG2))
+      _ARG2 = sexp_fp_mul(ctx, _ARG1, _ARG2);
+    else if (sexp_flonump(_ARG1) && sexp_fixnump(_ARG2))
+      _ARG2 = sexp_make_flonum(ctx, sexp_flonum_value(_ARG1) * (double)sexp_unbox_fixnum(_ARG2));
+    else if (sexp_fixnump(_ARG1) && sexp_flonump(_ARG2))
+      _ARG2 = sexp_make_flonum(ctx, (double)sexp_unbox_fixnum(_ARG1) * sexp_flonum_value(_ARG2));
+#endif
+    else sexp_raise("*: not a number", sexp_list2(ctx, _ARG1, _ARG2));
+#endif
+    top--;
+    break;
+  case SEXP_OP_DIV:
+    sexp_context_top(ctx) = top;
+    if (_ARG2 == SEXP_ZERO) {
+#if SEXP_USE_FLONUMS
+      if (sexp_flonump(_ARG1) && sexp_flonum_value(_ARG1) == 0.0)
+        _ARG2 = sexp_make_flonum(ctx, 0.0/0.0);
+      else
+#endif
+        sexp_raise("divide by zero", SEXP_NULL);
+    } else if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2)) {
+#if SEXP_USE_FLONUMS
+      _ARG1 = sexp_fixnum_to_flonum(ctx, _ARG1);
+      _ARG2 = sexp_fixnum_to_flonum(ctx, _ARG2);
+      _ARG2 = sexp_fp_div(ctx, _ARG1, _ARG2);
+      if (sexp_flonum_value(_ARG2) == trunc(sexp_flonum_value(_ARG2)))
+        _ARG2 = sexp_make_fixnum(sexp_flonum_value(_ARG2));
+#else
+      _ARG2 = sexp_fx_div(_ARG1, _ARG2);
+#endif
+    }
+#if SEXP_USE_BIGNUMS
+    else
+      _ARG2 = sexp_div(ctx, _ARG1, _ARG2);
+#else
+#if SEXP_USE_FLONUMS
+    else if (sexp_flonump(_ARG1) && sexp_flonump(_ARG2))
+      _ARG2 = sexp_fp_div(ctx, _ARG1, _ARG2);
+    else if (sexp_flonump(_ARG1) && sexp_fixnump(_ARG2))
+      _ARG2 = sexp_make_flonum(ctx, sexp_flonum_value(_ARG1) / (double)sexp_unbox_fixnum(_ARG2));
+    else if (sexp_fixnump(_ARG1) && sexp_flonump(_ARG2))
+      _ARG2 = sexp_make_flonum(ctx, (double)sexp_unbox_fixnum(_ARG1) / sexp_flonum_value(_ARG2));
+#endif
+    else sexp_raise("/: not a number", sexp_list2(ctx, _ARG1, _ARG2));
+#endif
+    top--;
+    break;
+  case SEXP_OP_QUOTIENT:
+    if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2)) {
+      if (_ARG2 == SEXP_ZERO)
+        sexp_raise("divide by zero", SEXP_NULL);
+      _ARG2 = sexp_fx_div(_ARG1, _ARG2);
+      top--;
+    }
+#if SEXP_USE_BIGNUMS
+    else {
+      sexp_context_top(ctx) = top;
+      _ARG2 = sexp_quotient(ctx, _ARG1, _ARG2);
+      top--;
+    }
+#else
+    else sexp_raise("quotient: not an integer", sexp_list2(ctx, _ARG1, _ARG2));
+#endif
+    break;
+  case SEXP_OP_REMAINDER:
+    if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2)) {
+      if (_ARG2 == SEXP_ZERO)
+        sexp_raise("divide by zero", SEXP_NULL);
+      tmp1 = sexp_fx_rem(_ARG1, _ARG2);
+      top--;
+      _ARG1 = tmp1;
+    }
+#if SEXP_USE_BIGNUMS
+    else {
+      sexp_context_top(ctx) = top;
+      _ARG2 = sexp_remainder(ctx, _ARG1, _ARG2);
+      top--;
+    }
+#else
+    else sexp_raise("remainder: not an integer", sexp_list2(ctx, _ARG1, _ARG2));
+#endif
+    break;
+  case SEXP_OP_LT:
+    if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2)) {
+      i = (sexp_sint_t)_ARG1 < (sexp_sint_t)_ARG2;
+#if SEXP_USE_BIGNUMS
+      _ARG2 = sexp_make_boolean(i);
+    } else {
+      tmp1 = sexp_compare(ctx, _ARG1, _ARG2);
+      _ARG2 = sexp_fixnump(tmp1)
+        ? sexp_make_boolean(sexp_unbox_fixnum(tmp1) < 0) : tmp1;
+    }
+#else
+#if SEXP_USE_FLONUMS
+    } else if (sexp_flonump(_ARG1) && sexp_flonump(_ARG2)) {
+      i = sexp_flonum_value(_ARG1) < sexp_flonum_value(_ARG2);
+    } else if (sexp_flonump(_ARG1) && sexp_fixnump(_ARG2)) {
+      i = sexp_flonum_value(_ARG1) < (double)sexp_unbox_fixnum(_ARG2); 
+    } else if (sexp_fixnump(_ARG1) && sexp_flonump(_ARG2)) {
+      i = (double)sexp_unbox_fixnum(_ARG1) < sexp_flonum_value(_ARG2);
+#endif
+    } else sexp_raise("<: not a number", sexp_list2(ctx, _ARG1, _ARG2));
+    _ARG2 = sexp_make_boolean(i);
+#endif
+    top--;
+    break;
+  case SEXP_OP_LE:
+    if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2)) {
+      i = (sexp_sint_t)_ARG1 <= (sexp_sint_t)_ARG2;
+#if SEXP_USE_BIGNUMS
+      _ARG2 = sexp_make_boolean(i);
+    } else {
+      tmp1 = sexp_compare(ctx, _ARG1, _ARG2);
+      _ARG2 = sexp_fixnump(tmp1)
+        ? sexp_make_boolean(sexp_unbox_fixnum(tmp1) <= 0) : tmp1;
+    }
+#else
+#if SEXP_USE_FLONUMS
+    } else if (sexp_flonump(_ARG1) && sexp_flonump(_ARG2)) {
+      i = sexp_flonum_value(_ARG1) <= sexp_flonum_value(_ARG2);
+    } else if (sexp_flonump(_ARG1) && sexp_fixnump(_ARG2)) {
+      i = sexp_flonum_value(_ARG1) <= (double)sexp_unbox_fixnum(_ARG2);
+    } else if (sexp_fixnump(_ARG1) && sexp_flonump(_ARG2)) {
+      i = (double)sexp_unbox_fixnum(_ARG1) <= sexp_flonum_value(_ARG2);
+#endif
+    } else sexp_raise("<=: not a number", sexp_list2(ctx, _ARG1, _ARG2));
+    _ARG2 = sexp_make_boolean(i);
+#endif
+    top--;
+    break;
+  case SEXP_OP_EQN:
+    if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2)) {
+      i = _ARG1 == _ARG2;
+#if SEXP_USE_BIGNUMS
+      _ARG2 = sexp_make_boolean(i);
+    } else {
+      tmp1 = sexp_compare(ctx, _ARG1, _ARG2);
+      _ARG2 = sexp_fixnump(tmp1)
+        ? sexp_make_boolean(sexp_unbox_fixnum(tmp1) == 0) : tmp1;
+    }
+#else
+#if SEXP_USE_FLONUMS
+    } else if (sexp_flonump(_ARG1) && sexp_flonump(_ARG2)) {
+      i = sexp_flonum_value(_ARG1) == sexp_flonum_value(_ARG2);
+    } else if (sexp_flonump(_ARG1) && sexp_fixnump(_ARG2)) {
+      i = sexp_flonum_value(_ARG1) == (double)sexp_unbox_fixnum(_ARG2);
+    } else if (sexp_fixnump(_ARG1) && sexp_flonump(_ARG2)) {
+      i = (double)sexp_unbox_fixnum(_ARG1) == sexp_flonum_value(_ARG2);
+#endif
+    } else sexp_raise("=: not a number", sexp_list2(ctx, _ARG1, _ARG2));
+    _ARG2 = sexp_make_boolean(i);
+#endif
+    top--;
+    break;
+  case SEXP_OP_EQ:
+    _ARG2 = sexp_make_boolean(_ARG1 == _ARG2);
+    top--;
+    break;
+  case SEXP_OP_FIX2FLO:
+    if (sexp_fixnump(_ARG1))
+      _ARG1 = sexp_fixnum_to_flonum(ctx, _ARG1);
+#if SEXP_USE_BIGNUMS
+    else if (sexp_bignump(_ARG1))
+      _ARG1 = sexp_make_flonum(ctx, sexp_bignum_to_double(_ARG1));
+#endif
+    else if (! sexp_flonump(_ARG1))
+      sexp_raise("exact->inexact: not a number", sexp_list1(ctx, _ARG1));
+    break;
+  case SEXP_OP_FLO2FIX:
+    if (sexp_flonump(_ARG1)) {
+      if (sexp_flonum_value(_ARG1) != trunc(sexp_flonum_value(_ARG1))) {
+        sexp_raise("inexact->exact: not an integer", sexp_list1(ctx, _ARG1));
+#if SEXP_USE_BIGNUMS
+      } else if ((sexp_flonum_value(_ARG1) > SEXP_MAX_FIXNUM)
+                 || sexp_flonum_value(_ARG1) < SEXP_MIN_FIXNUM) {
+        _ARG1 = sexp_double_to_bignum(ctx, sexp_flonum_value(_ARG1));
+#endif
+      } else {
+        _ARG1 = sexp_make_fixnum((sexp_sint_t)sexp_flonum_value(_ARG1));
+      }
+    } else if (! sexp_fixnump(_ARG1) && ! sexp_bignump(_ARG1)) {
+      sexp_raise("inexact->exact: not a number", sexp_list1(ctx, _ARG1));
+    }
+    break;
+  case SEXP_OP_CHAR2INT:
+    if (! sexp_charp(_ARG1))
+      sexp_raise("char->integer: not a character", sexp_list1(ctx, _ARG1));
+    _ARG1 = sexp_make_fixnum(sexp_unbox_character(_ARG1));
+    break;
+  case SEXP_OP_INT2CHAR:
+    if (! sexp_fixnump(_ARG1))
+      sexp_raise("integer->char: not an integer", sexp_list1(ctx, _ARG1));
+    _ARG1 = sexp_make_character(sexp_unbox_fixnum(_ARG1));
+    break;
+  case SEXP_OP_CHAR_UPCASE:
+    if (! sexp_charp(_ARG1))
+      sexp_raise("char-upcase: not a character", sexp_list1(ctx, _ARG1));
+    _ARG1 = sexp_make_character(toupper(sexp_unbox_character(_ARG1)));
+    break;
+  case SEXP_OP_CHAR_DOWNCASE:
+    if (! sexp_charp(_ARG1))
+      sexp_raise("char-downcase: not a character", sexp_list1(ctx, _ARG1));
+    _ARG1 = sexp_make_character(tolower(sexp_unbox_character(_ARG1)));
+    break;
+  case SEXP_OP_WRITE_CHAR:
+    if (! sexp_charp(_ARG1))
+      sexp_raise("write-char: not a character", sexp_list1(ctx, _ARG1));
+    if (! sexp_oportp(_ARG2))
+      sexp_raise("write-char: not an output-port", sexp_list1(ctx, _ARG2));
+    sexp_write_char(ctx, sexp_unbox_character(_ARG1), _ARG2);
+    _ARG2 = SEXP_VOID;
+    top--;
+    break;
+  case SEXP_OP_NEWLINE:
+    if (! sexp_oportp(_ARG1))
+      sexp_raise("newline: not an output-port", sexp_list1(ctx, _ARG1));
+    sexp_newline(ctx, _ARG1);
+    _ARG1 = SEXP_VOID;
+    break;
+  case SEXP_OP_READ_CHAR:
+    if (! sexp_iportp(_ARG1))
+      sexp_raise("read-char: not an intput-port", sexp_list1(ctx, _ARG1));
+    i = sexp_read_char(ctx, _ARG1);
+    _ARG1 = (i == EOF) ? SEXP_EOF : sexp_make_character(i);
+    break;
+  case SEXP_OP_PEEK_CHAR:
+    if (! sexp_iportp(_ARG1))
+      sexp_raise("peek-char: not an intput-port", sexp_list1(ctx, _ARG1));
+    i = sexp_read_char(ctx, _ARG1);
+    sexp_push_char(ctx, i, _ARG1);
+    _ARG1 = (i == EOF) ? SEXP_EOF : sexp_make_character(i);
+    break;
+  case SEXP_OP_RET:
+    i = sexp_unbox_fixnum(stack[fp]);
+    stack[fp-i] = _ARG1;
+    top = fp-i+1;
+    self = stack[fp+2];
+    bc = sexp_procedure_code(self);
+    ip = sexp_bytecode_data(bc) + sexp_unbox_fixnum(stack[fp+1]);
+    cp = sexp_procedure_vars(self);
+    fp = sexp_unbox_fixnum(stack[fp+3]);
+    break;
+  case SEXP_OP_DONE:
+    goto end_loop;
+  default:
+    sexp_raise("unknown opcode", sexp_list1(ctx, sexp_make_fixnum(*(ip-1))));
+  }
+  goto loop;
+
+ end_loop:
+  sexp_gc_release3(ctx);
+  sexp_context_top(ctx) = top;
+  return _ARG1;
+}
+