* load.c: change s_try_load and s_try_load_path to s_primitive_load

[bpt/guile.git] / libguile / eval.c

/*      Copyright (C) 1995,1996 Free Software Foundation, Inc.
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this software; see the file COPYING.  If not, write to
 * the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * As a special exception, the Free Software Foundation gives permission
 * for additional uses of the text contained in its release of GUILE.
 *
 * The exception is that, if you link the GUILE library with other files
 * to produce an executable, this does not by itself cause the
 * resulting executable to be covered by the GNU General Public License.
 * Your use of that executable is in no way restricted on account of
 * linking the GUILE library code into it.
 *
 * This exception does not however invalidate any other reasons why
 * the executable file might be covered by the GNU General Public License.
 *
 * This exception applies only to the code released by the
 * Free Software Foundation under the name GUILE.  If you copy
 * code from other Free Software Foundation releases into a copy of
 * GUILE, as the General Public License permits, the exception does
 * not apply to the code that you add in this way.  To avoid misleading
 * anyone as to the status of such modified files, you must delete
 * this exception notice from them.
 *
 * If you write modifications of your own for GUILE, it is your choice
 * whether to permit this exception to apply to your modifications.
 * If you do not wish that, delete this exception notice.  
 */
\f

/* This file is read twice in order to produce debugging versions of
 * scm_ceval and scm_apply.  These functions, scm_deval and
 * scm_dapply, are produced when we define the preprocessor macro
 * DEVAL.  The file is divided into sections which are treated
 * differently with respect to DEVAL.  The heads of these sections are
 * marked with the string "SECTION:".
 */


/* SECTION: This code is compiled once.
 */

#ifndef DEVAL

#include <stdio.h>
#include "_scm.h"
#include "debug.h"
#include "append.h"
#include "alist.h"
#include "sequences.h"
#include "eq.h"
#include "continuations.h"
#include "throw.h"
#include "smob.h"
#include "markers.h"
#include "procprop.h"
#include "hashtab.h"
#include "hash.h"

#ifdef DEBUG_EXTENSIONS
#include "debug.h"
#endif /* DEBUG_EXTENSIONS */

#include "srcprop.h"
#include "stackchk.h"

#include "eval.h"
\f

/* The evaluator contains a plethora of EVAL symbols.
 * This is an attempt at explanation.
 *
 * The following macros should be used in code which is read twice
 * (where the choice of evaluator is hard soldered):
 *
 *   SCM_CEVAL is the symbol used within one evaluator to call itself.
 *   Originally, it is defined to scm_ceval, but is redefined to
 *   scm_deval during the second pass.
 *  
 *   SIDEVAL corresponds to SCM_CEVAL, but is used in situations where
 *   only side effects of expressions matter.  All immediates are
 *   ignored.
 *  
 *   EVALIM is used when it is known that the expression is an
 *   immediate.  (This macro never calls an evaluator.)
 *  
 *   EVALCAR evaluates the car of an expression.
 *  
 *   EVALCELLCAR is like EVALCAR, but is used when it is known that the
 *   car is a lisp cell.
 *
 * The following macros should be used in code which is read once
 * (where the choice of evaluator is dynamic):
 *
 *   XEVAL takes care of immediates without calling an evaluator.  It
 *   then calls scm_ceval *or* scm_deval, depending on the debugging
 *   mode.
 *  
 *   XEVALCAR corresponds to EVALCAR, but uses scm_ceval *or* scm_deval
 *   depending on the debugging mode.
 *
 * The main motivation for keeping this plethora is efficiency
 * together with maintainability (=> locality of code).
 */

#define EVALCELLCAR(x, env) (SCM_SYMBOLP (SCM_CAR(x)) \
                             ? *scm_lookupcar(x, env) \
                             : SCM_CEVAL(SCM_CAR(x), env))

#ifdef MEMOIZE_LOCALS
#define EVALIM(x, env) (SCM_ILOCP(x)?*scm_ilookup((x), env):x)
#else
#define EVALIM(x, env) x
#endif
#define EVALCAR(x, env) (SCM_NCELLP(SCM_CAR(x))\
                        ? (SCM_IMP(SCM_CAR(x)) \
                           ? EVALIM(SCM_CAR(x), env) \
                           : SCM_GLOC_VAL(SCM_CAR(x))) \
                        : EVALCELLCAR(x, env))
#ifdef DEBUG_EXTENSIONS
#define XEVALCAR(x, env) (SCM_NCELLP(SCM_CAR(x)) \
                          ? (SCM_IMP(SCM_CAR(x)) \
                             ? EVALIM(SCM_CAR(x), env) \
                             : SCM_GLOC_VAL(SCM_CAR(x))) \
                          : (SCM_SYMBOLP(SCM_CAR(x)) \
                             ? *scm_lookupcar(x, env) \
                             : (*scm_ceval_ptr) (SCM_CAR(x), env)))
#else
#define XEVALCAR(x, env) EVALCAR(x, env)
#endif

#define EXTEND_ENV SCM_EXTEND_ENV

#ifdef MEMOIZE_LOCALS

SCM *
scm_ilookup (iloc, env)
     SCM iloc;
     SCM env;
{
  register int ir = SCM_IFRAME (iloc);
  register SCM er = env;
  for (; 0 != ir; --ir)
    er = SCM_CDR (er);
  er = SCM_CAR (er);
  for (ir = SCM_IDIST (iloc); 0 != ir; --ir)
    er = SCM_CDR (er);
  if (SCM_ICDRP (iloc))
    return SCM_CDRLOC (er);
  return SCM_CARLOC (SCM_CDR (er));
}
#endif


SCM *
scm_lookupcar (vloc, genv)
     SCM vloc;
     SCM genv;
{
  SCM env = genv;
  register SCM *al, fl, var = SCM_CAR (vloc);
#ifdef MEMOIZE_LOCALS
  register SCM iloc = SCM_ILOC00;
#endif
  for (; SCM_NIMP (env); env = SCM_CDR (env))
    {
      if (SCM_BOOL_T == scm_procedure_p (SCM_CAR (env)))
        break;
      al = SCM_CARLOC (env);
      for (fl = SCM_CAR (*al); SCM_NIMP (fl); fl = SCM_CDR (fl))
        {
          if (SCM_NCONSP (fl))
              if (fl == var)
              {
#ifdef MEMOIZE_LOCALS
                SCM_SETCAR (vloc, iloc + SCM_ICDR);
#endif
                return SCM_CDRLOC (*al);
              }
            else
              break;
          al = SCM_CDRLOC (*al);
          if (SCM_CAR (fl) == var)
            {
#ifdef MEMOIZE_LOCALS
#ifndef RECKLESS                /* letrec inits to SCM_UNDEFINED */
              if (SCM_UNBNDP (SCM_CAR (*al)))
                {
                  env = SCM_EOL;
                  goto errout;
                }
#endif
              SCM_SETCAR (vloc, iloc);
#endif
              return SCM_CARLOC (*al);
            }
#ifdef MEMOIZE_LOCALS
          iloc += SCM_IDINC;
#endif
        }
#ifdef MEMOIZE_LOCALS
      iloc = (~SCM_IDSTMSK) & (iloc + SCM_IFRINC);
#endif
    }
  {
    SCM top_thunk, vcell;
    if (SCM_NIMP(env))
      {
        top_thunk = SCM_CAR(env);       /* env now refers to a top level env thunk */
        env = SCM_CDR (env);
      }
    else
      top_thunk = SCM_BOOL_F;
    vcell = scm_sym2vcell (var, top_thunk, SCM_BOOL_F);
    if (vcell == SCM_BOOL_F)
      goto errout;
    else
      var = vcell;
  }
#ifndef RECKLESS
  if (SCM_NNULLP (env) || SCM_UNBNDP (SCM_CDR (var)))
    {
      var = SCM_CAR (var);
    errout:
      /* scm_everr (vloc, genv,...) */
      scm_misc_error (NULL,
                      SCM_NULLP (env)
                      ? "Unbound variable: %S"
                      : "Damaged environment: %S",
                      scm_listify (var, SCM_UNDEFINED));
    }
#endif
  SCM_SETCAR (vloc, var + 1);
  /* Except wait...what if the var is not a vcell,
   * but syntax or something....
   */
  return SCM_CDRLOC (var);
}

#define unmemocar scm_unmemocar

SCM 
scm_unmemocar (form, env)
     SCM form;
     SCM env;
{
#ifdef DEBUG_EXTENSIONS
  register int ir;
#endif
  SCM c;

  if (SCM_IMP (form))
    return form;
  c = SCM_CAR (form);
  if (1 == (c & 7))
    SCM_SETCAR (form, SCM_CAR (c - 1));
#ifdef MEMOIZE_LOCALS
#ifdef DEBUG_EXTENSIONS
  else if (SCM_ILOCP (c))
    {
      for (ir = SCM_IFRAME (c); ir != 0; --ir)
        env = SCM_CDR (env);
      env = SCM_CAR (SCM_CAR (env));
      for (ir = SCM_IDIST (c); ir != 0; --ir)
        env = SCM_CDR (env);
      SCM_SETCAR (form, SCM_ICDRP (c) ? env : SCM_CAR (env));
    }
#endif
#endif
  return form;
}


SCM
scm_eval_car (pair, env)
     SCM pair;
     SCM env;
{
  return XEVALCAR (pair, env);
}

\f
/* 
 * The following rewrite expressions and
 * some memoized forms have different syntax 
 */

static char s_expression[] = "missing or extra expression";
static char s_test[] = "bad test";
static char s_body[] = "bad body";
static char s_bindings[] = "bad bindings";
static char s_variable[] = "bad variable";
static char s_clauses[] = "bad or missing clauses";
static char s_formals[] = "bad formals";
#define ASSYNT(_cond, _arg, _pos, _subr) if(!(_cond))scm_wta(_arg, (char *)_pos, _subr);

SCM scm_i_dot, scm_i_quote, scm_i_quasiquote, scm_i_lambda, scm_i_let,
  scm_i_arrow, scm_i_else, scm_i_unquote, scm_i_uq_splicing, scm_i_apply;
SCM scm_i_define, scm_i_and, scm_i_begin, scm_i_case, scm_i_cond,
  scm_i_do, scm_i_if, scm_i_let, scm_i_letrec, scm_i_letstar,
  scm_i_or, scm_i_set, scm_i_atapply, scm_i_atcall_cc;
static char s_quasiquote[] = "quasiquote";
static char s_delay[] = "delay";
static char s_undefine[] = "undefine";
#ifdef DEBUG_EXTENSIONS
SCM scm_i_enter_frame, scm_i_apply_frame, scm_i_exit_frame;
SCM scm_i_trace;
#endif

#define ASRTSYNTAX(cond_, msg_) if(!(cond_))scm_wta(xorig, (msg_), what);



static void  bodycheck SCM_P ((SCM xorig, SCM *bodyloc, char *what));

static void 
bodycheck (xorig, bodyloc, what)
     SCM xorig;
     SCM *bodyloc;
     char *what;
{
  ASRTSYNTAX (scm_ilength (*bodyloc) >= 1, s_expression);
}



SCM 
scm_m_quote (xorig, env)
     SCM xorig;
     SCM env;
{
  ASSYNT (scm_ilength (SCM_CDR (xorig)) == 1, xorig, s_expression, "quote");
  return scm_cons (SCM_IM_QUOTE, SCM_CDR (xorig));
}



SCM 
scm_m_begin (xorig, env)
     SCM xorig;
     SCM env;
{
  ASSYNT (scm_ilength (SCM_CDR (xorig)) >= 1, xorig, s_expression, "begin");
  return scm_cons (SCM_IM_BEGIN, SCM_CDR (xorig));
}



SCM 
scm_m_if (xorig, env)
     SCM xorig;
     SCM env;
{
  int len = scm_ilength (SCM_CDR (xorig));
  ASSYNT (len >= 2 && len <= 3, xorig, s_expression, "if");
  return scm_cons (SCM_IM_IF, SCM_CDR (xorig));
}



SCM 
scm_m_set (xorig, env)
     SCM xorig;
     SCM env;
{
  SCM x = SCM_CDR (xorig);
  ASSYNT (2 == scm_ilength (x), xorig, s_expression, "set!");
  ASSYNT (SCM_NIMP (SCM_CAR (x)) && SCM_SYMBOLP (SCM_CAR (x)),
          xorig, s_variable, "set!");
  return scm_cons (SCM_IM_SET, x);
}


#if 0

SCM 
scm_m_vref (xorig, env)
     SCM xorig;
     SCM env;
{
  SCM x = SCM_CDR (xorig);
  ASSYNT (1 == scm_ilength (x), xorig, s_expression, s_vref);
  if (SCM_NIMP(x) && UDSCM_VARIABLEP (SCM_CAR (x)))
    {
      /* scm_everr (SCM_UNDEFINED, env,..., "global variable reference") */
      scm_misc_error (NULL,
                      "Bad variable: %S",
                      scm_listify (SCM_CAR (SCM_CDR (x)), SCM_UNDEFINED));
    }
  ASSYNT (SCM_NIMP(x) && DEFSCM_VARIABLEP (SCM_CAR (x)),
          xorig, s_variable, s_vref);
  return 
  return scm_cons (IM_VREF, x);
}



SCM 
scm_m_vset (xorig, env)
     SCM xorig;
     SCM env;
{
  SCM x = SCM_CDR (xorig);
  ASSYNT (3 == scm_ilength (x), xorig, s_expression, s_vset);
  ASSYNT ((   DEFSCM_VARIABLEP (SCM_CAR (x))
           || UDSCM_VARIABLEP (SCM_CAR (x))),
          xorig, s_variable, s_vset);
  return scm_cons (IM_VSET, x);
}
#endif 



SCM 
scm_m_and (xorig, env)
     SCM xorig;
     SCM env;
{
  int len = scm_ilength (SCM_CDR (xorig));
  ASSYNT (len >= 0, xorig, s_test, "and");
  if (len >= 1)
    return scm_cons (SCM_IM_AND, SCM_CDR (xorig));
  else
    return SCM_BOOL_T;
}



SCM 
scm_m_or (xorig, env)
     SCM xorig;
     SCM env;
{
  int len = scm_ilength (SCM_CDR (xorig));
  ASSYNT (len >= 0, xorig, s_test, "or");
  if (len >= 1)
    return scm_cons (SCM_IM_OR, SCM_CDR (xorig));
  else
    return SCM_BOOL_F;
}



SCM 
scm_m_case (xorig, env)
     SCM xorig;
     SCM env;
{
  SCM proc, x = SCM_CDR (xorig);
  ASSYNT (scm_ilength (x) >= 2, xorig, s_clauses, "case");
  while (SCM_NIMP (x = SCM_CDR (x)))
    {
      proc = SCM_CAR (x);
      ASSYNT (scm_ilength (proc) >= 2, xorig, s_clauses, "case");
      ASSYNT (scm_ilength (SCM_CAR (proc)) >= 0 || scm_i_else == SCM_CAR (proc),
              xorig, s_clauses, "case");
    }
  return scm_cons (SCM_IM_CASE, SCM_CDR (xorig));
}



SCM 
scm_m_cond (xorig, env)
     SCM xorig;
     SCM env;
{
  SCM arg1, x = SCM_CDR (xorig);
  int len = scm_ilength (x);
  ASSYNT (len >= 1, xorig, s_clauses, "cond");
  while (SCM_NIMP (x))
    {
      arg1 = SCM_CAR (x);
      len = scm_ilength (arg1);
      ASSYNT (len >= 1, xorig, s_clauses, "cond");
      if (scm_i_else == SCM_CAR (arg1))
        {
          ASSYNT (SCM_NULLP (SCM_CDR (x)) && len >= 2, xorig, "bad ELSE clause", "cond");
          SCM_SETCAR (arg1, SCM_BOOL_T);
        }
      if (len >= 2 && scm_i_arrow == SCM_CAR (SCM_CDR (arg1)))
        ASSYNT (3 == len && SCM_NIMP (SCM_CAR (SCM_CDR (SCM_CDR (arg1)))),
                xorig, "bad recipient", "cond");
      x = SCM_CDR (x);
    }
  return scm_cons (SCM_IM_COND, SCM_CDR (xorig));
}



SCM 
scm_m_lambda (xorig, env)
     SCM xorig;
     SCM env;
{
  SCM proc, x = SCM_CDR (xorig);
  if (scm_ilength (x) < 2)
    goto badforms;
  proc = SCM_CAR (x);
  if SCM_NULLP
    (proc) goto memlambda;
  if SCM_IMP
    (proc) goto badforms;
  if SCM_SYMBOLP
    (proc) goto memlambda;
  if SCM_NCONSP
    (proc) goto badforms;
  while SCM_NIMP
    (proc)
    {
      if SCM_NCONSP
        (proc)
          if (!SCM_SYMBOLP (proc))
          goto badforms;
        else
          goto memlambda;
      if (!(SCM_NIMP (SCM_CAR (proc)) && SCM_SYMBOLP (SCM_CAR (proc))))
        goto badforms;
      proc = SCM_CDR (proc);
    }
  if SCM_NNULLP
    (proc)
  badforms:scm_wta (xorig, s_formals, "lambda");
memlambda:
  bodycheck (xorig, SCM_CDRLOC (x), "lambda");
  return scm_cons (SCM_IM_LAMBDA, SCM_CDR (xorig));
}



SCM 
scm_m_letstar (xorig, env)
     SCM xorig;
     SCM env;
{
  SCM x = SCM_CDR (xorig), arg1, proc, vars = SCM_EOL, *varloc = &vars;
  int len = scm_ilength (x);
  ASSYNT (len >= 2, xorig, s_body, "let*");
  proc = SCM_CAR (x);
  ASSYNT (scm_ilength (proc) >= 0, xorig, s_bindings, "let*");
  while SCM_NIMP (proc)
    {
      arg1 = SCM_CAR (proc);
      ASSYNT (2 == scm_ilength (arg1), xorig, s_bindings, "let*");
      ASSYNT (SCM_NIMP (SCM_CAR (arg1)) && SCM_SYMBOLP (SCM_CAR (arg1)), xorig, s_variable, "let*");
      *varloc = scm_cons2 (SCM_CAR (arg1), SCM_CAR (SCM_CDR (arg1)), SCM_EOL);
      varloc = SCM_CDRLOC (SCM_CDR (*varloc));
      proc = SCM_CDR (proc);
    }
  x = scm_cons (vars, SCM_CDR (x));
  bodycheck (xorig, SCM_CDRLOC (x), "let*");
  return scm_cons (SCM_IM_LETSTAR, x);
}

/* DO gets the most radically altered syntax
   (do ((<var1> <init1> <step1>)
   (<var2> <init2>)
   ... )
   (<test> <return>)
   <body>)
   ;; becomes
   (do_mem (varn ... var2 var1)
   (<init1> <init2> ... <initn>)
   (<test> <return>)
   (<body>)
   <step1> <step2> ... <stepn>) ;; missing steps replaced by var
   */



SCM 
scm_m_do (xorig, env)
     SCM xorig;
     SCM env;
{
  SCM x = SCM_CDR (xorig), arg1, proc;
  SCM vars = SCM_EOL, inits = SCM_EOL, steps = SCM_EOL;
  SCM *initloc = &inits, *steploc = &steps;
  int len = scm_ilength (x);
  ASSYNT (len >= 2, xorig, s_test, "do");
  proc = SCM_CAR (x);
  ASSYNT (scm_ilength (proc) >= 0, xorig, s_bindings, "do");
  while SCM_NIMP
    (proc)
    {
      arg1 = SCM_CAR (proc);
      len = scm_ilength (arg1);
      ASSYNT (2 == len || 3 == len, xorig, s_bindings, "do");
      ASSYNT (SCM_NIMP (SCM_CAR (arg1)) && SCM_SYMBOLP (SCM_CAR (arg1)), xorig, s_variable, "do");
      /* vars reversed here, inits and steps reversed at evaluation */
      vars = scm_cons (SCM_CAR (arg1), vars);   /* variable */
      arg1 = SCM_CDR (arg1);
      *initloc = scm_cons (SCM_CAR (arg1), SCM_EOL);    /* init */
      initloc = SCM_CDRLOC (*initloc);
      arg1 = SCM_CDR (arg1);
      *steploc = scm_cons (SCM_IMP (arg1) ? SCM_CAR (vars) : SCM_CAR (arg1), SCM_EOL);  /* step */
      steploc = SCM_CDRLOC (*steploc);
      proc = SCM_CDR (proc);
    }
  x = SCM_CDR (x);
  ASSYNT (scm_ilength (SCM_CAR (x)) >= 1, xorig, s_test, "do");
  x = scm_cons2 (SCM_CAR (x), SCM_CDR (x), steps);
  x = scm_cons2 (vars, inits, x);
  bodycheck (xorig, SCM_CARLOC (SCM_CDR (SCM_CDR (x))), "do");
  return scm_cons (SCM_IM_DO, x);
}

/* evalcar is small version of inline EVALCAR when we don't care about
 * speed
 */
#define evalcar scm_eval_car


static SCM  iqq SCM_P ((SCM form, SCM env, int depth));

static SCM 
iqq (form, env, depth)
     SCM form;
     SCM env;
     int depth;
{
  SCM tmp;
  int edepth = depth;
  if SCM_IMP
    (form) return form;
  if (SCM_VECTORP (form))
    {
      long i = SCM_LENGTH (form);
      SCM *data = SCM_VELTS (form);
      tmp = SCM_EOL;
      for (; --i >= 0;)
        tmp = scm_cons (data[i], tmp);
      return scm_vector (iqq (tmp, env, depth));
    }
  if SCM_NCONSP
    (form) return form;
  tmp = SCM_CAR (form);
  if (scm_i_quasiquote == tmp)
    {
      depth++;
      goto label;
    }
  if (scm_i_unquote == tmp)
    {
      --depth;
    label:
      form = SCM_CDR (form);
      /* !!! might need a check here to be sure that form isn't a struct. */
      SCM_ASSERT (SCM_NIMP (form) && SCM_ECONSP (form) && SCM_NULLP (SCM_CDR (form)),
              form, SCM_ARG1, s_quasiquote);
      if (0 == depth)
        return evalcar (form, env);
      return scm_cons2 (tmp, iqq (SCM_CAR (form), env, depth), SCM_EOL);
    }
  if (SCM_NIMP (tmp) && (scm_i_uq_splicing == SCM_CAR (tmp)))
    {
      tmp = SCM_CDR (tmp);
      if (0 == --edepth)
        return scm_append (scm_cons2 (evalcar (tmp, env), iqq (SCM_CDR (form), env, depth), SCM_EOL));
    }
  return scm_cons (iqq (SCM_CAR (form), env, edepth), iqq (SCM_CDR (form), env, depth));
}

/* Here are acros which return values rather than code. */


SCM 
scm_m_quasiquote (xorig, env)
     SCM xorig;
     SCM env;
{
  SCM x = SCM_CDR (xorig);
  ASSYNT (scm_ilength (x) == 1, xorig, s_expression, s_quasiquote);
  return iqq (SCM_CAR (x), env, 1);
}


SCM 
scm_m_delay (xorig, env)
     SCM xorig;
     SCM env;
{
  ASSYNT (scm_ilength (xorig) == 2, xorig, s_expression, s_delay);
  xorig = SCM_CDR (xorig);
  return scm_makprom (scm_closure (scm_cons2 (SCM_EOL, SCM_CAR (xorig), SCM_CDR (xorig)),
                                   env));
}


static SCM env_top_level SCM_P ((SCM env));

static SCM
env_top_level (env)
     SCM env;
{
  while (SCM_NIMP(env))
    {
      if (SCM_BOOL_T == scm_procedure_p (SCM_CAR(env)))
        return SCM_CAR(env);
      env = SCM_CDR (env);
    }
  return SCM_BOOL_F;
}


SCM 
scm_m_define (x, env)
     SCM x;
     SCM env;
{
  SCM proc, arg1 = x;
  x = SCM_CDR (x);
  /*  ASSYNT(SCM_NULLP(env), x, "bad placement", s_define);*/
  ASSYNT (scm_ilength (x) >= 2, arg1, s_expression, "define");
  proc = SCM_CAR (x);
  x = SCM_CDR (x);
  while (SCM_NIMP (proc) && SCM_CONSP (proc))
    {                           /* nested define syntax */
      x = scm_cons (scm_cons2 (scm_i_lambda, SCM_CDR (proc), x), SCM_EOL);
      proc = SCM_CAR (proc);
    }
  ASSYNT (SCM_NIMP (proc) && SCM_SYMBOLP (proc), arg1, s_variable, "define");
  ASSYNT (1 == scm_ilength (x), arg1, s_expression, "define");
  if (SCM_TOP_LEVEL (env))
    {
      x = evalcar (x, env);
#ifdef DEBUG_EXTENSIONS
      if (SCM_REC_PROCNAMES_P)
        scm_set_procedure_property_x (x, scm_i_name, proc);
#endif
      arg1 = scm_sym2vcell (proc, env_top_level (env), SCM_BOOL_T);
#if 0
#ifndef RECKLESS
      if (SCM_NIMP (SCM_CDR (arg1)) && ((SCM) SCM_SNAME (SCM_CDR (arg1)) == proc)
          && (SCM_CDR (arg1) != x))
        scm_warn ("redefining built-in ", SCM_CHARS (proc));
      else
#endif
      if (5 <= scm_verbose && SCM_UNDEFINED != SCM_CDR (arg1))
        scm_warn ("redefining ", SCM_CHARS (proc));
#endif
      SCM_SETCDR (arg1, x);
#ifdef SICP
      return scm_cons2 (scm_i_quote, SCM_CAR (arg1), SCM_EOL);
#else
      return SCM_UNSPECIFIED;
#endif
    }
  return scm_cons2 (SCM_IM_DEFINE, proc, x);
}

SCM
scm_m_undefine (x, env)
     SCM x, env;
{
  SCM arg1 = x;
  x = SCM_CDR (x);
  ASSYNT (SCM_TOP_LEVEL (env), arg1, "bad placement ", s_undefine);
  ASSYNT (SCM_NIMP (x) && SCM_CONSP (x) && SCM_CDR (x) == SCM_EOL,
          arg1, s_expression, s_undefine);
  x = SCM_CAR (x);
  ASSYNT (SCM_NIMP (x) && SCM_SYMBOLP (x), arg1, s_variable, s_undefine);
  arg1 = scm_sym2vcell (x, env_top_level (env), SCM_BOOL_F);
  ASSYNT (SCM_NFALSEP (arg1) && !SCM_UNBNDP (SCM_CDR (arg1)),
          x, "variable already unbound ", s_undefine);
#if 0
#ifndef RECKLESS
  if (SCM_NIMP (SCM_CDR (arg1)) && ((SCM) SCM_SNAME (SCM_CDR (arg1)) == x))
    scm_warn ("undefining built-in ", SCM_CHARS (x));
  else
#endif
    if (5 <= scm_verbose && SCM_UNDEFINED != SCM_CDR (arg1))
      scm_warn ("redefining ", SCM_CHARS (x));
#endif
  SCM_SETCDR (arg1, SCM_UNDEFINED);
#ifdef SICP
  return SCM_CAR (arg1);
#else
  return SCM_UNSPECIFIED;
#endif
}

/* end of acros */


SCM 
scm_m_letrec (xorig, env)
     SCM xorig;
     SCM env;
{
  SCM cdrx = SCM_CDR (xorig);   /* locally mutable version of form */
  char *what = SCM_CHARS (SCM_CAR (xorig));
  SCM x = cdrx, proc, arg1;     /* structure traversers */
  SCM vars = SCM_EOL, inits = SCM_EOL, *initloc = &inits;

  ASRTSYNTAX (scm_ilength (x) >= 2, s_body);
  proc = SCM_CAR (x);
  if SCM_NULLP
    (proc) return scm_m_letstar (xorig, env);   /* null binding, let* faster */
  ASRTSYNTAX (scm_ilength (proc) >= 1, s_bindings);
  do
    {
      /* vars scm_list reversed here, inits reversed at evaluation */
      arg1 = SCM_CAR (proc);
      ASRTSYNTAX (2 == scm_ilength (arg1), s_bindings);
      ASRTSYNTAX (SCM_NIMP (SCM_CAR (arg1)) && SCM_SYMBOLP (SCM_CAR (arg1)), s_variable);
      vars = scm_cons (SCM_CAR (arg1), vars);
      *initloc = scm_cons (SCM_CAR (SCM_CDR (arg1)), SCM_EOL);
      initloc = SCM_CDRLOC (*initloc);
    }
  while SCM_NIMP
  (proc = SCM_CDR (proc));
  cdrx = scm_cons2 (vars, inits, SCM_CDR (x));
  bodycheck (xorig, SCM_CDRLOC (SCM_CDR (cdrx)), what);
  return scm_cons (SCM_IM_LETREC, cdrx);
}


SCM 
scm_m_let (xorig, env)
     SCM xorig;
     SCM env;
{
  SCM cdrx = SCM_CDR (xorig);   /* locally mutable version of form */
  SCM x = cdrx, proc, arg1, name;       /* structure traversers */
  SCM vars = SCM_EOL, inits = SCM_EOL, *varloc = &vars, *initloc = &inits;

  ASSYNT (scm_ilength (x) >= 2, xorig, s_body, "let");
  proc = SCM_CAR (x);
  if (SCM_NULLP (proc)
      || (SCM_NIMP (proc) && SCM_CONSP (proc)
          && SCM_NIMP (SCM_CAR (proc)) && SCM_CONSP (SCM_CAR (proc)) && SCM_NULLP (SCM_CDR (proc))))
    return scm_m_letstar (xorig, env);  /* null or single binding, let* is faster */
  ASSYNT (SCM_NIMP (proc), xorig, s_bindings, "let");
  if (SCM_CONSP (proc))                 /* plain let, proc is <bindings> */
      return scm_cons (SCM_IM_LET, SCM_CDR (scm_m_letrec (xorig, env)));
  if (!SCM_SYMBOLP (proc))
    scm_wta (xorig, s_bindings, "let"); /* bad let */
  name = proc;                  /* named let, build equiv letrec */
  x = SCM_CDR (x);
  ASSYNT (scm_ilength (x) >= 2, xorig, s_body, "let");
  proc = SCM_CAR (x);           /* bindings scm_list */
  ASSYNT (scm_ilength (proc) >= 0, xorig, s_bindings, "let");
  while SCM_NIMP
    (proc)
    {                           /* vars and inits both in order */
      arg1 = SCM_CAR (proc);
      ASSYNT (2 == scm_ilength (arg1), xorig, s_bindings, "let");
      ASSYNT (SCM_NIMP (SCM_CAR (arg1)) && SCM_SYMBOLP (SCM_CAR (arg1)), xorig, s_variable, "let");
      *varloc = scm_cons (SCM_CAR (arg1), SCM_EOL);
      varloc = SCM_CDRLOC (*varloc);
      *initloc = scm_cons (SCM_CAR (SCM_CDR (arg1)), SCM_EOL);
      initloc = SCM_CDRLOC (*initloc);
      proc = SCM_CDR (proc);
    }
  return
    scm_m_letrec (scm_cons2 (scm_i_let,
                             scm_cons (scm_cons2 (name, scm_cons2 (scm_i_lambda, vars, SCM_CDR (x)), SCM_EOL), SCM_EOL),
                             scm_acons (name, inits, SCM_EOL)),         /* body */
                  env);
}



SCM 
scm_m_apply (xorig, env)
     SCM xorig;
     SCM env;
{
  ASSYNT (scm_ilength (SCM_CDR (xorig)) == 2, xorig, s_expression, "@apply");
  return scm_cons (SCM_IM_APPLY, SCM_CDR (xorig));
}

#define s_atcall_cc (SCM_ISYMCHARS(SCM_IM_CONT)+1)


SCM 
scm_m_cont (xorig, env)
     SCM xorig;
     SCM env;
{
  ASSYNT (scm_ilength (SCM_CDR (xorig)) == 1, xorig, s_expression, "@call-with-current-continuation");
  return scm_cons (SCM_IM_CONT, SCM_CDR (xorig));
}

/* scm_unmemocopy takes a memoized expression together with its
 * environment and rewrites it to its original form.  Thus, it is the
 * inversion of the rewrite rules above.  The procedure is not
 * optimized for speed.  It's used in scm_iprin1 when printing the
 * code of a closure, in scm_procedure_source and in scm_expr_stack
 * when generating the source for a stackframe.
 */


static SCM unmemocopy SCM_P ((SCM x, SCM env));

static SCM
unmemocopy (x, env)
     SCM x;
     SCM env;
{
  SCM ls, z;
#ifdef DEBUG_EXTENSIONS
  SCM p;
#endif
  if (SCM_NCELLP (x) || SCM_NECONSP (x))
    return x;
#ifdef DEBUG_EXTENSIONS
  p = scm_whash_lookup (scm_source_whash, x);
#endif
  switch (SCM_TYP7 (x))
    {
    case (127 & SCM_IM_AND):
      ls = z = scm_cons (scm_i_and, SCM_UNSPECIFIED);
      break;
    case (127 & SCM_IM_BEGIN):
      ls = z = scm_cons (scm_i_begin, SCM_UNSPECIFIED);
      break;
    case (127 & SCM_IM_CASE):
      ls = z = scm_cons (scm_i_case, SCM_UNSPECIFIED);
      break;
    case (127 & SCM_IM_COND):
      ls = z = scm_cons (scm_i_cond, SCM_UNSPECIFIED);
      break;
    case (127 & SCM_IM_DO):
      ls = scm_cons (scm_i_do, SCM_UNSPECIFIED);
      goto transform;
    case (127 & SCM_IM_IF):
      ls = z = scm_cons (scm_i_if, SCM_UNSPECIFIED);
      break;
    case (127 & SCM_IM_LET):
      ls = scm_cons (scm_i_let, SCM_UNSPECIFIED);
      goto transform;
    case (127 & SCM_IM_LETREC):
      {
        SCM f, v, e, s;
        ls = scm_cons (scm_i_letrec, SCM_UNSPECIFIED);
      transform:
        x = SCM_CDR (x);
        f = v = SCM_CAR (x);
        x = SCM_CDR (x);
        z = EXTEND_ENV (f, SCM_EOL, env);
        e = scm_reverse (unmemocopy (SCM_CAR (x),
                                     SCM_CAR (ls) == scm_i_letrec ? z : env));
        env = z;
        s = SCM_CAR (ls) == scm_i_do
            ? scm_reverse (unmemocopy (SCM_CDR (SCM_CDR (SCM_CDR (x))), env))
            : f;
        z = SCM_EOL;
        do
          {
            z = scm_acons (SCM_CAR (v),
                           scm_cons (SCM_CAR (e),
                                     SCM_CAR (s) == SCM_CAR (v)
                                     ? SCM_EOL
                                     : scm_cons (SCM_CAR (s), SCM_EOL)),
                           z);
            v = SCM_CDR (v);
            e = SCM_CDR (e);
            s = SCM_CDR (s);
          }
        while SCM_NIMP (v);
        z = scm_cons (z, SCM_UNSPECIFIED);
        SCM_SETCDR (ls, z);
        if (SCM_CAR (ls) == scm_i_do)
          {
            x = SCM_CDR (x);
            SCM_SETCDR (z, scm_cons (unmemocopy (SCM_CAR (x), env),
                                     SCM_UNSPECIFIED));
            z = SCM_CDR (z);
            x = (SCM) (SCM_CARLOC (SCM_CDR (x)) - 1);
          }
        break;
      }
    case (127 & SCM_IM_LETSTAR):
      {
        SCM b, y;
        x = SCM_CDR (x);
        b = SCM_CAR (x);
        y = SCM_EOL;
        if SCM_IMP (b)
          {
            env = EXTEND_ENV (SCM_EOL, SCM_EOL, env);
            goto letstar;
          }
        y = z = scm_acons (SCM_CAR (b),
                           unmemocar (
        scm_cons (unmemocopy (SCM_CAR (SCM_CDR (b)), env), SCM_EOL), env),
                           SCM_UNSPECIFIED);
        env = EXTEND_ENV (SCM_CAR (b), SCM_BOOL_F, env);
        b = SCM_CDR (SCM_CDR (b));
        if (SCM_IMP (b))
          {
            SCM_SETCDR (y, SCM_EOL);
            ls = scm_cons (scm_i_let, z = scm_cons (y, SCM_UNSPECIFIED));
            break;
          }
        do
          {
            SCM_SETCDR (z, scm_acons (SCM_CAR (b),
                                      unmemocar (
            scm_cons (unmemocopy (SCM_CAR (SCM_CDR (b)), env), SCM_EOL), env),
                                      SCM_UNSPECIFIED));
            z = SCM_CDR (z);
            env = EXTEND_ENV (SCM_CAR (b), SCM_BOOL_F, env);
            b = SCM_CDR (SCM_CDR (b));
          }
        while SCM_NIMP (b);
        SCM_SETCDR (z, SCM_EOL);
      letstar:
        ls = scm_cons (scm_i_letstar, z = scm_cons (y, SCM_UNSPECIFIED));
        break;
      }
    case (127 & SCM_IM_OR):
      ls = z = scm_cons (scm_i_or, SCM_UNSPECIFIED);
      break;
    case (127 & SCM_IM_LAMBDA):
      x = SCM_CDR (x);
      ls = scm_cons (scm_i_lambda,
                     z = scm_cons (SCM_CAR (x), SCM_UNSPECIFIED));
      env = EXTEND_ENV (SCM_CAR (x), SCM_EOL, env);
      break;
    case (127 & SCM_IM_QUOTE):
      ls = z = scm_cons (scm_i_quote, SCM_UNSPECIFIED);
      break;
    case (127 & SCM_IM_SET):
      ls = z = scm_cons (scm_i_set, SCM_UNSPECIFIED);
      break;
    case (127 & SCM_IM_DEFINE):
      {
        SCM n;
        x = SCM_CDR (x);
        ls = scm_cons (scm_i_define,
                       z = scm_cons (n = SCM_CAR (x), SCM_UNSPECIFIED));
        if (SCM_NNULLP (env))
          SCM_SETCAR (SCM_CAR (env), scm_cons (n, SCM_CAR (SCM_CAR (env))));
        break;
      }
    case (127 & SCM_MAKISYM (0)):
      z = SCM_CAR (x);
      if (!SCM_ISYMP (z))
        goto unmemo;
      switch SCM_ISYMNUM (z)
        {
        case (SCM_ISYMNUM (SCM_IM_APPLY)):
          ls = z = scm_cons (scm_i_atapply, SCM_UNSPECIFIED);
          goto loop;
        case (SCM_ISYMNUM (SCM_IM_CONT)):
          ls = z = scm_cons (scm_i_atcall_cc, SCM_UNSPECIFIED);
          goto loop;
        default:
        }
    unmemo:
    default:
      ls = z = unmemocar (scm_cons (unmemocopy (SCM_CAR (x), env),
                                    SCM_UNSPECIFIED),
                          env);
    }
loop:
  while (SCM_CELLP (x = SCM_CDR (x)) && SCM_ECONSP (x))
    {
      SCM_SETCDR (z, unmemocar (scm_cons (unmemocopy (SCM_CAR (x), env),
                                          SCM_UNSPECIFIED),
                                env));
      z = SCM_CDR (z);
    }
  SCM_SETCDR (z, x);
#ifdef DEBUG_EXTENSIONS
  if (SCM_NFALSEP (p))
    scm_whash_insert (scm_source_whash, ls, p);
#endif
  return ls;
}


SCM
scm_unmemocopy (x, env)
     SCM x;
     SCM env;
{
  if (SCM_NNULLP (env))
    /* Make a copy of the lowest frame to protect it from
       modifications by SCM_IM_DEFINE */
    return unmemocopy (x, scm_cons (SCM_CAR (env), SCM_CDR (env)));
  else
    return unmemocopy (x, env);
}

#ifndef RECKLESS

int 
scm_badargsp (formals, args)
     SCM formals;
     SCM args;
{
  while SCM_NIMP
    (formals)
    {
      if SCM_NCONSP
        (formals) return 0;
      if SCM_IMP
        (args) return 1;
      formals = SCM_CDR (formals);
      args = SCM_CDR (args);
    }
  return SCM_NNULLP (args) ? 1 : 0;
}
#endif


\f
long scm_tc16_macro;


SCM 
scm_eval_args (l, env)
     SCM l;
     SCM env;
{
  SCM res = SCM_EOL, *lloc = &res;
  while (SCM_NIMP (l))
    {
      *lloc = scm_cons (EVALCAR (l, env), SCM_EOL);
      lloc = SCM_CDRLOC (*lloc);
      l = SCM_CDR (l);
    }
  return res;
}
#endif /* !DEVAL */


/* SECTION: This code is specific for the debugging support.  One
 * branch is read when DEVAL isn't defined, the other when DEVAL is
 * defined.
 */

#ifndef DEVAL

#define SCM_APPLY scm_apply
#define PREP_APPLY(proc, args)
#define ENTER_APPLY
#define RETURN(x) return x;
#ifdef STACK_CHECKING
#ifndef NO_CEVAL_STACK_CHECKING
#define EVAL_STACK_CHECKING
#endif
#endif

#else /* !DEVAL */

#undef SCM_CEVAL
#define SCM_CEVAL scm_deval     /* Substitute all uses of scm_ceval */
#undef SCM_APPLY
#define SCM_APPLY scm_dapply
#undef PREP_APPLY
#define PREP_APPLY(p, l) \
{ ++debug.info; debug.info->a.proc = p; debug.info->a.args = l; }
#undef ENTER_APPLY
#define ENTER_APPLY \
{\
  SCM_SET_ARGSREADY (debug);\
  if (CHECK_APPLY)\
    if (SCM_APPLY_FRAME_P || (SCM_TRACE_P && PROCTRACEP (proc)))\
      {\
        SCM tmp, tail = SCM_TRACED_FRAME_P (debug) ? SCM_BOOL_T : SCM_BOOL_F;\
        SCM_SET_TRACED_FRAME (debug);\
        if (SCM_CHEAPTRAPS_P)\
          {\
            tmp = scm_make_debugobj ((scm_debug_frame *) &debug);\
            scm_ithrow (scm_i_apply_frame, scm_cons2 (tmp, tail, SCM_EOL), 0);\
          }\
        else\
          {\
            scm_make_cont (&tmp);\
            if (!setjmp (SCM_JMPBUF (tmp)))\
              scm_ithrow (scm_i_apply_frame, scm_cons2 (tmp, tail, SCM_EOL), 0);\
          }\
      }\
}
#undef RETURN
#define RETURN(e) {proc = (e); goto exit;}
#ifdef STACK_CHECKING
#ifndef EVAL_STACK_CHECKING
#define EVAL_STACK_CHECKING
#endif
#endif

/* scm_ceval_ptr points to the currently selected evaluator.
 * *fixme*: Although efficiency is important here, this state variable
 * should probably not be a global.  It should be related to the
 * current repl.
 */


SCM (*scm_ceval_ptr) SCM_P ((SCM x, SCM env));

/* scm_last_debug_frame contains a pointer to the last debugging
 * information stack frame.  It is accessed very often from the
 * debugging evaluator, so it should probably not be indirectly
 * addressed.  Better to save and restore it from the current root at
 * any stack swaps.
 */

#ifndef USE_THREADS
scm_debug_frame *scm_last_debug_frame;
#endif

/* scm_debug_eframe_size is the number of slots available for pseudo
 * stack frames at each real stack frame.
 */

int scm_debug_eframe_size;

int scm_debug_mode, scm_check_entry_p, scm_check_apply_p, scm_check_exit_p;

scm_option scm_debug_opts[] = {
  { SCM_OPTION_BOOLEAN, "cheap", 1,
    "*Flyweight representation of the stack at traps." },
  { SCM_OPTION_BOOLEAN, "breakpoints", 0, "*Check for breakpoints." },
  { SCM_OPTION_BOOLEAN, "trace", 0, "*Trace mode." },
  { SCM_OPTION_BOOLEAN, "procnames", 1,
    "Record procedure names at definition." },
  { SCM_OPTION_BOOLEAN, "backwards", 0,
    "Display backtrace in anti-chronological order." },
  { SCM_OPTION_INTEGER, "indent", 10, "Maximal indentation in backtrace." },
  { SCM_OPTION_INTEGER, "frames", 3,
    "Maximum number of tail-recursive frames in backtrace." },
  { SCM_OPTION_INTEGER, "maxdepth", 1000,
    "Maximal number of stored backtrace frames." },
  { SCM_OPTION_INTEGER, "depth", 20, "Maximal length of printed backtrace." },
  { SCM_OPTION_BOOLEAN, "backtrace", 1,
    "Show backtrace on error (use debugging evaluator)." },
  { SCM_OPTION_BOOLEAN, "deval", 0, "Use the debugging evaluator." },
  { SCM_OPTION_INTEGER, "stack", 20000, "Stack size limit (0 = no check)." }
};

scm_option scm_evaluator_trap_table[] = {
  { SCM_OPTION_BOOLEAN, "enter-frame", 0, "Trap when eval enters new frame." },
  { SCM_OPTION_BOOLEAN, "apply-frame", 0, "Trap when entering apply." },
  { SCM_OPTION_BOOLEAN, "exit-frame", 0, "Trap when exiting eval or apply." }
};

SCM
scm_deval_args (l, env, lloc)
     SCM l, env, *lloc;
{
  SCM *res = lloc;
  while (SCM_NIMP (l))
    {
      *lloc = scm_cons (EVALCAR (l, env), SCM_EOL);
      lloc = SCM_CDRLOC (*lloc);
      l = SCM_CDR (l);
    }
  return *res;
}

#endif /* !DEVAL */


/* SECTION: Some local definitions for the evaluator.
 */

#ifndef DEVAL
#ifdef SCM_FLOATS
#define CHECK_EQVISH(A,B)       (((A) == (B)) || (SCM_NFALSEP (scm_eqv_p ((A), (B)))))
#else
#define CHECK_EQVISH(A,B)       ((A) == (B))
#endif
#endif /* DEVAL */


/* SECTION: This is the evaluator.  Like any real monster, it has
 * three heads.  This code is compiled twice.
 */

#if 0

SCM 
scm_ceval (x, env)
     SCM x;
     SCM env;
{}
#endif
#if 0

SCM 
scm_deval (x, env)
     SCM x;
     SCM env;
{}
#endif


SCM 
SCM_CEVAL (x, env)
     SCM x;
     SCM env;
{
  union
    {
      SCM *lloc;
      SCM arg1;
    } t;
  SCM proc, arg2;
#ifdef DEVAL
  struct
  {
    scm_debug_frame *prev;
    long status;
    scm_debug_info vect[scm_debug_eframe_size];
    scm_debug_info *info;
  } debug;
  debug.prev = scm_last_debug_frame;
  debug.status = scm_debug_eframe_size;
  debug.info = &debug.vect[0];
  scm_last_debug_frame = (scm_debug_frame *) &debug;
#endif
#ifdef EVAL_STACK_CHECKING
  if (SCM_STACK_OVERFLOW_P ((SCM_STACKITEM *) &proc)
      && scm_stack_checking_enabled_p)
    {
#ifdef DEVAL
      debug.info->e.exp = x;
      debug.info->e.env = env;
#endif
      scm_report_stack_overflow ();
    }
#endif
#ifdef DEVAL
  goto start;
#endif
loopnoap:
  PREP_APPLY (SCM_UNDEFINED, SCM_EOL);
loop:
#ifdef DEVAL
#if 0 /* This will probably never have any practical use ... */
  if (CHECK_EXIT)
    {
      if (SINGLE_STEP || (SCM_TRACE_P && SCM_TRACED_FRAME_P (debug)))
        {
          SINGLE_STEP = 0;
          SCM_RESET_DEBUG_MODE;
          SCM_CLEAR_TRACED_FRAME (debug);
          scm_make_cont (&t.arg1);
          if (!setjmp (SCM_JMPBUF (t.arg1)))
            scm_ithrow (scm_i_exit_tail, scm_cons (t.arg1, SCM_EOL), 0);
        }
    }
nextframe:
#endif
  SCM_CLEAR_ARGSREADY (debug);
  if (SCM_OVERFLOWP (debug))
    --debug.info;
  else if (++debug.info == (scm_debug_info *) &debug.info)
    {
      SCM_SET_OVERFLOW (debug);
      debug.info -= 2;
    }
start:
  debug.info->e.exp = x;
  debug.info->e.env = env;
  if (CHECK_ENTRY)
    if (SCM_ENTER_FRAME_P || (SCM_BREAKPOINTS_P && SRCBRKP (x)))
      {
        SCM tail = SCM_TAILRECP (debug) ? SCM_BOOL_T : SCM_BOOL_F;
        SCM_SET_TAILREC (debug);
        SCM_ENTER_FRAME_P = 0;
        SCM_RESET_DEBUG_MODE;
        if (SCM_CHEAPTRAPS_P)
          t.arg1 = scm_make_debugobj ((scm_debug_frame *) &debug);
        else
          {
            scm_make_cont (&t.arg1);
            if (setjmp (SCM_JMPBUF (t.arg1)))
              {
                x = SCM_THROW_VALUE (t.arg1);
                if (SCM_IMP (x))
                  {
                    RETURN (x);
                  }
                else
                  /* This gives the possibility for the debugger to
                     modify the source expression before evaluation. */
                  goto dispatch;
              }
          }
        scm_ithrow (scm_i_enter_frame,
                    scm_cons2 (t.arg1, tail,
                               scm_cons (scm_unmemocopy (x, env), SCM_EOL)),
                    0);
      }
dispatch:
#endif
  SCM_ASYNC_TICK;
  switch (SCM_TYP7 (x))
    {
    case scm_tcs_symbols:
      /* Only happens when called at top level.
       */
      x = scm_cons (x, SCM_UNDEFINED);
      goto retval;

    case (127 & SCM_IM_AND):
      x = SCM_CDR (x);
      t.arg1 = x;
      while (SCM_NNULLP (t.arg1 = SCM_CDR (t.arg1)))
        if (SCM_FALSEP (EVALCAR (x, env)))
          {
            RETURN (SCM_BOOL_F);
          }
        else
          x = t.arg1;
      PREP_APPLY (SCM_UNDEFINED, SCM_EOL);
      goto carloop;

    case (127 & SCM_IM_BEGIN):
    cdrxnoap:
      PREP_APPLY (SCM_UNDEFINED, SCM_EOL);
    cdrxbegin:
      x = SCM_CDR (x);

    begin:
      t.arg1 = x;
      while (SCM_NNULLP (t.arg1 = SCM_CDR (t.arg1)))
        {
          SIDEVAL (SCM_CAR (x), env);
          x = t.arg1;
        }

    carloop:                    /* scm_eval car of last form in list */
      if (SCM_NCELLP (SCM_CAR (x)))
        {
          x = SCM_CAR (x);
          RETURN (SCM_IMP (x) ? EVALIM (x, env) : SCM_GLOC_VAL (x))
        }

      if (SCM_SYMBOLP (SCM_CAR (x)))
        {
        retval:
          RETURN (*scm_lookupcar (x, env))
        }

      x = SCM_CAR (x);
      goto loop;                /* tail recurse */


    case (127 & SCM_IM_CASE):
      x = SCM_CDR (x);
      t.arg1 = EVALCAR (x, env);
      while (SCM_NIMP (x = SCM_CDR (x)))
        {
          proc = SCM_CAR (x);
          if (scm_i_else == SCM_CAR (proc))
            {
              x = SCM_CDR (proc);
              PREP_APPLY (SCM_UNDEFINED, SCM_EOL);
              goto begin;
            }
          proc = SCM_CAR (proc);
          while (SCM_NIMP (proc))
            {
              if (CHECK_EQVISH (SCM_CAR (proc), t.arg1))
                {
                  x = SCM_CDR (SCM_CAR (x));
                  PREP_APPLY (SCM_UNDEFINED, SCM_EOL);
                  goto begin;
                }
              proc = SCM_CDR (proc);
            }
        }
      RETURN (SCM_UNSPECIFIED)


    case (127 & SCM_IM_COND):
      while (SCM_NIMP (x = SCM_CDR (x)))
        {
          proc = SCM_CAR (x);
          t.arg1 = EVALCAR (proc, env);
          if (SCM_NFALSEP (t.arg1))
            {
              x = SCM_CDR (proc);
              if SCM_NULLP (x)
                {
                  RETURN (t.arg1)
                }
              if (scm_i_arrow != SCM_CAR (x))
                {
                  PREP_APPLY (SCM_UNDEFINED, SCM_EOL);
                  goto begin;
                }
              proc = SCM_CDR (x);
              proc = EVALCAR (proc, env);
              SCM_ASRTGO (SCM_NIMP (proc), badfun);
              PREP_APPLY (proc, scm_cons (t.arg1, SCM_EOL));
              ENTER_APPLY;
              goto evap1;
            }
        }
      RETURN (SCM_UNSPECIFIED)


    case (127 & SCM_IM_DO):
      x = SCM_CDR (x);
      proc = SCM_CAR (SCM_CDR (x)); /* inits */
      t.arg1 = SCM_EOL;         /* values */
      while (SCM_NIMP (proc))
        {
          t.arg1 = scm_cons (EVALCAR (proc, env), t.arg1);
          proc = SCM_CDR (proc);
        }
      env = EXTEND_ENV (SCM_CAR (x), t.arg1, env);
      x = SCM_CDR (SCM_CDR (x));
      while (proc = SCM_CAR (x), SCM_FALSEP (EVALCAR (proc, env)))
        {
          for (proc = SCM_CAR (SCM_CDR (x)); SCM_NIMP (proc); proc = SCM_CDR (proc))
            {
              t.arg1 = SCM_CAR (proc); /* body */
              SIDEVAL (t.arg1, env);
            }
          for (t.arg1 = SCM_EOL, proc = SCM_CDR (SCM_CDR (x)); SCM_NIMP (proc); proc = SCM_CDR (proc))
            t.arg1 = scm_cons (EVALCAR (proc, env), t.arg1); /* steps */
          env = EXTEND_ENV (SCM_CAR (SCM_CAR (env)), t.arg1, SCM_CDR (env));
        }
      x = SCM_CDR (proc);
      if (SCM_NULLP (x))
        RETURN (SCM_UNSPECIFIED);
      PREP_APPLY (SCM_UNDEFINED, SCM_EOL);
      goto begin;


    case (127 & SCM_IM_IF):
      x = SCM_CDR (x);
      if (SCM_NFALSEP (EVALCAR (x, env)))
        x = SCM_CDR (x);
      else if (SCM_IMP (x = SCM_CDR (SCM_CDR (x))))
        {
          RETURN (SCM_UNSPECIFIED);
        }
      PREP_APPLY (SCM_UNDEFINED, SCM_EOL);
      goto carloop;


    case (127 & SCM_IM_LET):
      x = SCM_CDR (x);
      proc = SCM_CAR (SCM_CDR (x));
      t.arg1 = SCM_EOL;
      do
        {
          t.arg1 = scm_cons (EVALCAR (proc, env), t.arg1);
        }
      while (SCM_NIMP (proc = SCM_CDR (proc)));
      env = EXTEND_ENV (SCM_CAR (x), t.arg1, env);
      x = SCM_CDR (x);
      goto cdrxnoap;


    case (127 & SCM_IM_LETREC):
      x = SCM_CDR (x);
      env = EXTEND_ENV (SCM_CAR (x), scm_undefineds, env);
      x = SCM_CDR (x);
      proc = SCM_CAR (x);
      t.arg1 = SCM_EOL;
      do
        {
          t.arg1 = scm_cons (EVALCAR (proc, env), t.arg1);
        }
      while (SCM_NIMP (proc = SCM_CDR (proc)));
      SCM_SETCDR (SCM_CAR (env), t.arg1);
      goto cdrxnoap;


    case (127 & SCM_IM_LETSTAR):
      x = SCM_CDR (x);
      proc = SCM_CAR (x);
      if (SCM_IMP (proc))
        {
          env = EXTEND_ENV (SCM_EOL, SCM_EOL, env);
          goto cdrxnoap;
        }
      do
        {
          t.arg1 = SCM_CAR (proc);
          proc = SCM_CDR (proc);
          env = EXTEND_ENV (t.arg1, EVALCAR (proc, env), env);
        }
      while (SCM_NIMP (proc = SCM_CDR (proc)));
      goto cdrxnoap;

    case (127 & SCM_IM_OR):
      x = SCM_CDR (x);
      t.arg1 = x;
      while (SCM_NNULLP (t.arg1 = SCM_CDR (t.arg1)))
        {
          x = EVALCAR (x, env);
          if (SCM_NFALSEP (x))
            {
              RETURN (x);
            }
          x = t.arg1;
        }
      PREP_APPLY (SCM_UNDEFINED, SCM_EOL);
      goto carloop;


    case (127 & SCM_IM_LAMBDA):
      RETURN (scm_closure (SCM_CDR (x), env));


    case (127 & SCM_IM_QUOTE):
      RETURN (SCM_CAR (SCM_CDR (x)));


    case (127 & SCM_IM_SET):
      x = SCM_CDR (x);
      proc = SCM_CAR (x);
      switch (7 & (int) proc)
        {
        case 0:
          t.lloc = scm_lookupcar (x, env);
          break;
        case 1:
          t.lloc = SCM_GLOC_VAL_LOC (proc);
          break;
#ifdef MEMOIZE_LOCALS
        case 4:
          t.lloc = scm_ilookup (proc, env);
          break;
#endif
        }
      x = SCM_CDR (x);
      *t.lloc = EVALCAR (x, env);
#ifdef SICP
      RETURN (*t.lloc);
#else
      RETURN (SCM_UNSPECIFIED);
#endif


    case (127 & SCM_IM_DEFINE): /* only for internal defines */
      x = SCM_CDR (x);
      proc = SCM_CAR (x);
      x = SCM_CDR (x);
      x = evalcar (x, env);
#ifdef DEBUG_EXTENSIONS
      if (SCM_REC_PROCNAMES_P && SCM_NIMP (x) && SCM_CLOSUREP (x))
        scm_set_procedure_property_x (x, scm_i_name, proc);
#endif
      env = SCM_CAR (env);
      SCM_DEFER_INTS;
      SCM_SETCAR (env, scm_cons (proc, SCM_CAR (env)));
      SCM_SETCDR (env, scm_cons (x, SCM_CDR (env)));
      SCM_ALLOW_INTS;
      RETURN (SCM_UNSPECIFIED);



      /* new syntactic forms go here. */
    case (127 & SCM_MAKISYM (0)):
      proc = SCM_CAR (x);
      SCM_ASRTGO (SCM_ISYMP (proc), badfun);
      switch SCM_ISYMNUM (proc)
        {
#if 0
        case (SCM_ISYMNUM (IM_VREF)):
          {
            SCM var;
            var = SCM_CAR (SCM_CDR (x));
            RETURN (SCM_CDR(var));
          }
        case (SCM_ISYMNUM (IM_VSET)):
          SCM_CDR (SCM_CAR ( SCM_CDR (x))) = EVALCAR( SCM_CDR ( SCM_CDR (x)), env);
          SCM_CAR (SCM_CAR ( SCM_CDR (x))) = scm_tc16_variable;
          RETURN (SCM_UNSPECIFIED)
#endif

        case (SCM_ISYMNUM (SCM_IM_APPLY)):
          proc = SCM_CDR (x);
          proc = EVALCAR (proc, env);
          SCM_ASRTGO (SCM_NIMP (proc), badfun);
          if (SCM_CLOSUREP (proc))
            {
              PREP_APPLY (proc, SCM_EOL);
              t.arg1 = SCM_CDR (SCM_CDR (x));
              t.arg1 = EVALCAR (t.arg1, env);
#ifdef DEVAL
              debug.info->a.args = t.arg1;
#endif
#ifndef RECKLESS
              if (scm_badargsp (SCM_CAR (SCM_CODE (proc)), t.arg1))
                goto wrongnumargs;
#endif
              env = EXTEND_ENV (SCM_CAR (SCM_CODE (proc)), t.arg1, SCM_ENV (proc));
              x = SCM_CODE (proc);
              goto cdrxbegin;
            }
          proc = scm_i_apply;
          goto evapply;

        case (SCM_ISYMNUM (SCM_IM_CONT)):
          scm_make_cont (&t.arg1);
          if (setjmp (SCM_JMPBUF (t.arg1)))
            {
              SCM val;
              val = SCM_THROW_VALUE (t.arg1);
              RETURN (val);
            }
          proc = SCM_CDR (x);
          proc = evalcar (proc, env);
          SCM_ASRTGO (SCM_NIMP (proc), badfun);
          PREP_APPLY (proc, scm_cons (t.arg1, SCM_EOL));
          ENTER_APPLY;
          goto evap1;

        default:
          goto badfun;
        }

    default:
      proc = x;
    badfun:
      /* scm_everr (x, env,...) */
      scm_misc_error (NULL,
                      "Wrong type to apply: %S",
                      scm_listify (proc, SCM_UNDEFINED));
    case scm_tc7_vector:
    case scm_tc7_wvect:
    case scm_tc7_bvect:
    case scm_tc7_byvect:
    case scm_tc7_svect:
    case scm_tc7_ivect:
    case scm_tc7_uvect:
    case scm_tc7_fvect:
    case scm_tc7_dvect:
    case scm_tc7_cvect:
#ifdef LONGLONGS
    case scm_tc7_llvect:
#endif
    case scm_tc7_string:
    case scm_tc7_mb_string:
    case scm_tc7_substring:
    case scm_tc7_mb_substring:
    case scm_tc7_smob:
    case scm_tcs_closures:
    case scm_tcs_subrs:
      RETURN (x);

#ifdef MEMOIZE_LOCALS
    case (127 & SCM_ILOC00):
      proc = *scm_ilookup (SCM_CAR (x), env);
      SCM_ASRTGO (SCM_NIMP (proc), badfun);
#ifndef RECKLESS
#ifdef CAUTIOUS
      goto checkargs;
#endif
#endif
      break;
#endif /* ifdef MEMOIZE_LOCALS */


    case scm_tcs_cons_gloc:
      proc = SCM_GLOC_VAL (SCM_CAR (x));
      SCM_ASRTGO (SCM_NIMP (proc), badfun);
#ifndef RECKLESS
#ifdef CAUTIOUS
      goto checkargs;
#endif
#endif
      break;


    case scm_tcs_cons_nimcar:
      if (SCM_SYMBOLP (SCM_CAR (x)))
        {
          proc = *scm_lookupcar (x, env);
          if (SCM_IMP (proc))
            {
              unmemocar (x, env);
              goto badfun;
            }
          if (scm_tc16_macro == SCM_TYP16 (proc))
            {
              unmemocar (x, env);

            handle_a_macro:
              t.arg1 = SCM_APPLY (SCM_CDR (proc), x, scm_cons (env, scm_listofnull));
              switch ((int) (SCM_CAR (proc) >> 16))
                {
                case 2:
                  if (scm_ilength (t.arg1) <= 0)
                    t.arg1 = scm_cons2 (SCM_IM_BEGIN, t.arg1, SCM_EOL);
#ifdef DEVAL
                  if (!SCM_CLOSUREP (SCM_CDR (proc)))
                    {
#if 0 /* Top-level defines doesn't very often occur in backtraces */
                      if (scm_m_define == SCM_SUBRF (SCM_CDR (proc)) && SCM_TOP_LEVEL (env))
                        /* Prevent memoizing result of define macro */
                        {
                          debug.info->e.exp = scm_cons (SCM_CAR (x), SCM_CDR (x));
                          scm_set_source_properties_x (debug.info->e.exp,
                                                       scm_source_properties (x));
                        }
#endif
                      SCM_DEFER_INTS;
                      SCM_SETCAR (x, SCM_CAR (t.arg1));
                      SCM_SETCDR (x, SCM_CDR (t.arg1));
                      SCM_ALLOW_INTS;
                      goto dispatch;
                    }
                  /* Prevent memoizing of debug info expression. */
                  debug.info->e.exp = scm_cons (SCM_CAR (x), SCM_CDR (x));
                  scm_set_source_properties_x (debug.info->e.exp,
                                               scm_source_properties (x));
#endif
                  SCM_DEFER_INTS;
                  SCM_SETCAR (x, SCM_CAR (t.arg1));
                  SCM_SETCDR (x, SCM_CDR (t.arg1));
                  SCM_ALLOW_INTS;
                  goto loopnoap;
                case 1:
                  if (SCM_NIMP (x = t.arg1))
                    goto loopnoap;
                case 0:
                  RETURN (t.arg1);
                }
            }
        }
      else
        proc = SCM_CEVAL (SCM_CAR (x), env);
      SCM_ASRTGO (SCM_NIMP (proc), badfun);
#ifndef RECKLESS
#ifdef CAUTIOUS
    checkargs:
#endif
      if (SCM_CLOSUREP (proc))
        {
          arg2 = SCM_CAR (SCM_CODE (proc));
          t.arg1 = SCM_CDR (x);
          while (SCM_NIMP (arg2))
            {
              if (SCM_NCONSP (arg2))
                goto evapply;
              if (SCM_IMP (t.arg1))
                goto umwrongnumargs;
              arg2 = SCM_CDR (arg2);
              t.arg1 = SCM_CDR (t.arg1);
            }
          if (SCM_NNULLP (t.arg1))
            goto umwrongnumargs;
        }
      else if (scm_tc16_macro == SCM_TYP16 (proc))
        goto handle_a_macro;
#endif
    }


evapply:
  PREP_APPLY (proc, SCM_EOL);
  if (SCM_NULLP (SCM_CDR (x))) {
    ENTER_APPLY;
    switch (SCM_TYP7 (proc))
      {                         /* no arguments given */
      case scm_tc7_subr_0:
        RETURN (SCM_SUBRF (proc) ());
      case scm_tc7_subr_1o:
        RETURN (SCM_SUBRF (proc) (SCM_UNDEFINED));
      case scm_tc7_lsubr:
        RETURN (SCM_SUBRF (proc) (SCM_EOL));
      case scm_tc7_rpsubr:
        RETURN (SCM_BOOL_T);
      case scm_tc7_asubr:
        RETURN (SCM_SUBRF (proc) (SCM_UNDEFINED, SCM_UNDEFINED));
#ifdef CCLO
      case scm_tc7_cclo:
        t.arg1 = proc;
        proc = SCM_CCLO_SUBR (proc);
#ifdef DEVAL
        debug.info->a.proc = proc;
        debug.info->a.args = scm_cons (t.arg1, SCM_EOL);
#endif
        goto evap1;
#endif
      case scm_tcs_closures:
        x = SCM_CODE (proc);
        env = EXTEND_ENV (SCM_CAR (x), SCM_EOL, SCM_ENV (proc));
        goto cdrxbegin;
      case scm_tc7_contin:
      case scm_tc7_subr_1:
      case scm_tc7_subr_2:
      case scm_tc7_subr_2o:
      case scm_tc7_cxr:
      case scm_tc7_subr_3:
      case scm_tc7_lsubr_2:
      umwrongnumargs:
        unmemocar (x, env);
      wrongnumargs:
        /* scm_everr (x, env,...)  */
        scm_wrong_num_args (proc);
      default:
        /* handle macros here */
        goto badfun;
      }
  }

  /* must handle macros by here */
  x = SCM_CDR (x);
#ifdef CAUTIOUS
  if (SCM_IMP (x))
    goto wrongnumargs;
#endif
  t.arg1 = EVALCAR (x, env);
#ifdef DEVAL
  debug.info->a.args = scm_cons (t.arg1, SCM_EOL);
#endif
  x = SCM_CDR (x);
  if (SCM_NULLP (x))
    {
      ENTER_APPLY;
    evap1:
      switch (SCM_TYP7 (proc))
        {                               /* have one argument in t.arg1 */
        case scm_tc7_subr_2o:
          RETURN (SCM_SUBRF (proc) (t.arg1, SCM_UNDEFINED));
        case scm_tc7_subr_1:
        case scm_tc7_subr_1o:
          RETURN (SCM_SUBRF (proc) (t.arg1));
        case scm_tc7_cxr:
#ifdef SCM_FLOATS
          if (SCM_SUBRF (proc))
            {
              if (SCM_INUMP (t.arg1))
                {
                  RETURN (scm_makdbl (SCM_DSUBRF (proc) ((double) SCM_INUM (t.arg1)),
                                      0.0));
                }
              SCM_ASRTGO (SCM_NIMP (t.arg1), floerr);
              if (SCM_REALP (t.arg1))
                {
                  RETURN (scm_makdbl (SCM_DSUBRF (proc) (SCM_REALPART (t.arg1)), 0.0));
                }
#ifdef SCM_BIGDIG
              if (SCM_BIGP (t.arg1))
                {
                  RETURN (scm_makdbl (SCM_DSUBRF (proc) (scm_big2dbl (t.arg1)), 0.0));
                }
#endif
            floerr:
              scm_wta (t.arg1, (char *) SCM_ARG1, SCM_CHARS (SCM_SNAME (proc)));
            }
#endif
          proc = (SCM) SCM_SNAME (proc);
          {
            char *chrs = SCM_CHARS (proc) + SCM_LENGTH (proc) - 1;
            while ('c' != *--chrs)
              {
                SCM_ASSERT (SCM_NIMP (t.arg1) && SCM_CONSP (t.arg1),
                            t.arg1, SCM_ARG1, SCM_CHARS (proc));
                t.arg1 = ('a' == *chrs) ? SCM_CAR (t.arg1) : SCM_CDR (t.arg1);
              }
            RETURN (t.arg1);
          }
        case scm_tc7_rpsubr:
          RETURN (SCM_BOOL_T);
        case scm_tc7_asubr:
          RETURN (SCM_SUBRF (proc) (t.arg1, SCM_UNDEFINED));
        case scm_tc7_lsubr:
#ifdef DEVAL
          RETURN (SCM_SUBRF (proc) (debug.info->a.args))
#else
          RETURN (SCM_SUBRF (proc) (scm_cons (t.arg1, SCM_EOL)));
#endif
#ifdef CCLO
        case scm_tc7_cclo:
          arg2 = t.arg1;
          t.arg1 = proc;
          proc = SCM_CCLO_SUBR (proc);
#ifdef DEVAL
          debug.info->a.args = scm_cons (t.arg1, debug.info->a.args);
          debug.info->a.proc = proc;
#endif
          goto evap2;
#endif
        case scm_tcs_closures:
          x = SCM_CODE (proc);
#ifdef DEVAL
          env = EXTEND_ENV (SCM_CAR (x), debug.info->a.args, SCM_ENV (proc));
#else
          env = EXTEND_ENV (SCM_CAR (x), scm_cons (t.arg1, SCM_EOL), SCM_ENV (proc));
#endif
          goto cdrxbegin;
        case scm_tc7_contin:
          scm_call_continuation (proc, t.arg1);
        case scm_tc7_subr_2:
        case scm_tc7_subr_0:
        case scm_tc7_subr_3:
        case scm_tc7_lsubr_2:
          goto wrongnumargs;
        default:
          goto badfun;
        }
    }
#ifdef CAUTIOUS
  if (SCM_IMP (x))
    goto wrongnumargs;
#endif
  {                             /* have two or more arguments */
    arg2 = EVALCAR (x, env);
#ifdef DEVAL
    debug.info->a.args = scm_cons2 (t.arg1, arg2, SCM_EOL);
#endif
    x = SCM_CDR (x);
    if (SCM_NULLP (x)) {
      ENTER_APPLY;
#ifdef CCLO
    evap2:
#endif
      switch (SCM_TYP7 (proc))
        {                       /* have two arguments */
        case scm_tc7_subr_2:
        case scm_tc7_subr_2o:
          RETURN (SCM_SUBRF (proc) (t.arg1, arg2));
        case scm_tc7_lsubr:
#ifdef DEVAL
          RETURN (SCM_SUBRF (proc) (debug.info->a.args))
#else
          RETURN (SCM_SUBRF (proc) (scm_cons2 (t.arg1, arg2, SCM_EOL)));
#endif
        case scm_tc7_lsubr_2:
          RETURN (SCM_SUBRF (proc) (t.arg1, arg2, SCM_EOL));
        case scm_tc7_rpsubr:
        case scm_tc7_asubr:
          RETURN (SCM_SUBRF (proc) (t.arg1, arg2));
#ifdef CCLO
        cclon:
        case scm_tc7_cclo:
#ifdef DEVAL
          RETURN (SCM_APPLY (SCM_CCLO_SUBR (proc), proc,
                             scm_cons (debug.info->a.args, SCM_EOL)));
#else
          RETURN (SCM_APPLY (SCM_CCLO_SUBR (proc), proc,
                             scm_cons2 (t.arg1, arg2,
                                        scm_cons (scm_eval_args (x, env), SCM_EOL))));
#endif
          /*    case scm_tc7_cclo:
                x = scm_cons(arg2, scm_eval_args(x, env));
                arg2 = t.arg1;
                t.arg1 = proc;
                proc = SCM_CCLO_SUBR(proc);
                goto evap3; */
#endif
        case scm_tc7_subr_0:
        case scm_tc7_cxr:
        case scm_tc7_subr_1o:
        case scm_tc7_subr_1:
        case scm_tc7_subr_3:
        case scm_tc7_contin:
          goto wrongnumargs;
        default:
          goto badfun;
        case scm_tcs_closures:
#ifdef DEVAL
          env = EXTEND_ENV (SCM_CAR (SCM_CODE (proc)), debug.info->a.args, SCM_ENV (proc));
#else
          env = EXTEND_ENV (SCM_CAR (SCM_CODE (proc)), scm_cons2 (t.arg1, arg2, SCM_EOL), SCM_ENV (proc));
#endif
          x = SCM_CODE (proc);
          goto cdrxbegin;
        }
    }
#ifdef DEVAL
    debug.info->a.args = scm_cons2 (t.arg1, arg2,
            scm_deval_args (x, env, SCM_CDRLOC (SCM_CDR (debug.info->a.args))));
#endif
    ENTER_APPLY;
    switch (SCM_TYP7 (proc))
      {                 /* have 3 or more arguments */
#ifdef DEVAL
      case scm_tc7_subr_3:
        SCM_ASRTGO (SCM_NULLP (SCM_CDR (x)), wrongnumargs);
        RETURN (SCM_SUBRF (proc) (t.arg1, arg2, SCM_CAR (SCM_CDR (SCM_CDR (debug.info->a.args)))));
      case scm_tc7_asubr:
        /*      t.arg1 = SCM_SUBRF(proc)(t.arg1, arg2);
                while SCM_NIMP(x) {
                t.arg1 = SCM_SUBRF(proc)(t.arg1, EVALCAR(x, env));
                x = SCM_CDR(x);
                }
                RETURN (t.arg1) */
      case scm_tc7_rpsubr:
        RETURN (SCM_APPLY (proc, t.arg1, scm_acons (arg2, SCM_CDR (SCM_CDR (debug.info->a.args)), SCM_EOL)))
          case scm_tc7_lsubr_2:
            RETURN (SCM_SUBRF (proc) (t.arg1, arg2, SCM_CDR (SCM_CDR (debug.info->a.args))))
          case scm_tc7_lsubr:
            RETURN (SCM_SUBRF (proc) (debug.info->a.args))
#ifdef CCLO
      case scm_tc7_cclo:
        goto cclon;
#endif
      case scm_tcs_closures:
        SCM_SET_ARGSREADY (debug);
        env = EXTEND_ENV (SCM_CAR (SCM_CODE (proc)),
                              debug.info->a.args,
                              SCM_ENV (proc));
        x = SCM_CODE (proc);
        goto cdrxbegin;
#else /* DEVAL */
      case scm_tc7_subr_3:
        SCM_ASRTGO (SCM_NULLP (SCM_CDR (x)), wrongnumargs);
        RETURN (SCM_SUBRF (proc) (t.arg1, arg2, EVALCAR (x, env)));
      case scm_tc7_asubr:
        /*      t.arg1 = SCM_SUBRF(proc)(t.arg1, arg2);
                while SCM_NIMP(x) {
                t.arg1 = SCM_SUBRF(proc)(t.arg1, EVALCAR(x, env));
                x = SCM_CDR(x);
                }
                RETURN (t.arg1) */
      case scm_tc7_rpsubr:
        RETURN (SCM_APPLY (proc, t.arg1, scm_acons (arg2, scm_eval_args (x, env), SCM_EOL)));
      case scm_tc7_lsubr_2:
        RETURN (SCM_SUBRF (proc) (t.arg1, arg2, scm_eval_args (x, env)));
      case scm_tc7_lsubr:
        RETURN (SCM_SUBRF (proc) (scm_cons2 (t.arg1, arg2, scm_eval_args (x, env))));
#ifdef CCLO
      case scm_tc7_cclo:
        goto cclon;
#endif
      case scm_tcs_closures:
#ifdef DEVAL
        SCM_SET_ARGSREADY (debug);
#endif
        env = EXTEND_ENV (SCM_CAR (SCM_CODE (proc)),
                              scm_cons2 (t.arg1, arg2, scm_eval_args (x, env)),
                              SCM_ENV (proc));
        x = SCM_CODE (proc);
        goto cdrxbegin;
#endif /* DEVAL */
      case scm_tc7_subr_2:
      case scm_tc7_subr_1o:
      case scm_tc7_subr_2o:
      case scm_tc7_subr_0:
      case scm_tc7_cxr:
      case scm_tc7_subr_1:
      case scm_tc7_contin:
        goto wrongnumargs;
      default:
        goto badfun;
      }
  }
#ifdef DEVAL
exit:
  if (CHECK_EXIT)
    if (SCM_EXIT_FRAME_P || (SCM_TRACE_P && SCM_TRACED_FRAME_P (debug)))
      {
        SCM_EXIT_FRAME_P = 0;
        SCM_RESET_DEBUG_MODE;
        SCM_CLEAR_TRACED_FRAME (debug);
        if (SCM_CHEAPTRAPS_P)
          t.arg1 = scm_make_debugobj ((scm_debug_frame *) &debug);
        else
          {
            scm_make_cont (&t.arg1);
            if (setjmp (SCM_JMPBUF (t.arg1)))
              {
                proc = SCM_THROW_VALUE (t.arg1);
                goto ret;
              }
          }
        scm_ithrow (scm_i_exit_frame, scm_cons2 (t.arg1, proc, SCM_EOL), 0);
      }
ret:
  scm_last_debug_frame = debug.prev;
  return proc;
#endif
}


/* SECTION: This code is compiled once.
 */

#ifndef DEVAL

SCM_PROC(s_procedure_documentation, "procedure-documentation", 1, 0, 0, scm_procedure_documentation);

SCM 
scm_procedure_documentation (proc)
     SCM proc;
{
  SCM code;
  SCM_ASSERT (SCM_BOOL_T == scm_procedure_p (proc) && SCM_NIMP (proc) && SCM_TYP7 (proc) != scm_tc7_contin,
          proc, SCM_ARG1, s_procedure_documentation);
  switch (SCM_TYP7 (proc))
    {
    case scm_tcs_closures:
      code = SCM_CDR (SCM_CODE (proc));
      if (SCM_IMP (SCM_CDR (code)))
        return SCM_BOOL_F;
      code = SCM_CAR (code);
      if (SCM_IMP (code))
        return SCM_BOOL_F;
      if (SCM_STRINGP (code))
        return code;
    default:
      return SCM_BOOL_F;
/*
  case scm_tcs_subrs:
#ifdef CCLO
  case scm_tc7_cclo:
#endif
*/
    }
}

/* This code processes the 'arg ...' parameters to apply.

   (apply PROC ARG1 ... ARGS)

   The ARG1 ... arguments are consed on to the front of ARGS (which
   must be a list), and then PROC is applied to the elements of the
   result.  apply:nconc2last takes care of building the list of
   arguments, given (ARG1 ... ARGS).

   apply:nconc2last destroys its argument.  On that topic, this code
   came into my care with the following beautifully cryptic comment on
   that topic: "This will only screw you if you do (scm_apply
   scm_apply '( ... ))"  If you know what they're referring to, send
   me a patch to this comment.  */

SCM_PROC(s_nconc2last, "apply:nconc2last", 1, 0, 0, scm_nconc2last);

SCM 
scm_nconc2last (lst)
     SCM lst;
{
  SCM *lloc;
  SCM_ASSERT (scm_ilength (lst) > 0, lst, SCM_ARG1, s_nconc2last);
  lloc = &lst;
  while (SCM_NNULLP (SCM_CDR (*lloc)))
    lloc = SCM_CDRLOC (*lloc);
  SCM_ASSERT (scm_ilength (SCM_CAR (*lloc)) >= 0, lst, SCM_ARG1, s_nconc2last);
  *lloc = SCM_CAR (*lloc);
  return lst;
}

#endif /* !DEVAL */


/* SECTION: When DEVAL is defined this code yields scm_dapply.
 * It is compiled twice.
 */

#if 0

SCM 
scm_apply (proc, arg1, args)
     SCM proc;
     SCM arg1;
     SCM args;
{}
#endif

#if 0

SCM 
scm_dapply (proc, arg1, args)
     SCM proc;
     SCM arg1;
     SCM args;
{}
#endif


SCM 
SCM_APPLY (proc, arg1, args)
     SCM proc;
     SCM arg1;
     SCM args;
{
#ifdef DEBUG_EXTENSIONS
#ifdef DEVAL
  scm_debug_frame debug;
  debug.prev = scm_last_debug_frame;
  debug.status = SCM_APPLYFRAME;
  debug.vect[0].a.proc = proc;
  debug.vect[0].a.args = SCM_EOL;
  scm_last_debug_frame = &debug;
#else
  if (SCM_DEBUGGINGP)
    return scm_dapply (proc, arg1, args);
#endif
#endif

  SCM_ASRTGO (SCM_NIMP (proc), badproc);
  if (SCM_NULLP (args))
    {
      if (SCM_NULLP (arg1))
        arg1 = SCM_UNDEFINED;
      else
        {
          args = SCM_CDR (arg1);
          arg1 = SCM_CAR (arg1);
        }
    }
  else
    {
      /*                SCM_ASRTGO(SCM_NIMP(args) && SCM_CONSP(args), wrongnumargs); */
      args = scm_nconc2last (args);
    }
#ifdef DEVAL
  debug.vect[0].a.args = scm_cons (arg1, args);
  if (SCM_ENTER_FRAME_P)
    {
      SCM tmp;
      SCM_ENTER_FRAME_P = 0;
      SCM_RESET_DEBUG_MODE;
      if (SCM_CHEAPTRAPS_P)
        tmp = scm_make_debugobj ((scm_debug_frame *) &debug);
      else
        {
          scm_make_cont (&tmp);
          if (setjmp (SCM_JMPBUF (tmp)))
            goto entap;
        }
      scm_ithrow (scm_i_enter_frame, scm_cons (tmp, SCM_EOL), 0);
    }
entap:
  ENTER_APPLY;
#endif
#ifdef CCLO
tail:
#endif
  switch (SCM_TYP7 (proc))
    {
    case scm_tc7_subr_2o:
      args = SCM_NULLP (args) ? SCM_UNDEFINED : SCM_CAR (args);
      RETURN (SCM_SUBRF (proc) (arg1, args))
    case scm_tc7_subr_2:
      SCM_ASRTGO (SCM_NULLP (SCM_CDR (args)), wrongnumargs);
      args = SCM_CAR (args);
      RETURN (SCM_SUBRF (proc) (arg1, args))
    case scm_tc7_subr_0:
      SCM_ASRTGO (SCM_UNBNDP (arg1), wrongnumargs);
      RETURN (SCM_SUBRF (proc) ())
    case scm_tc7_subr_1:
    case scm_tc7_subr_1o:
      SCM_ASRTGO (SCM_NULLP (args), wrongnumargs);
      RETURN (SCM_SUBRF (proc) (arg1))
    case scm_tc7_cxr:
      SCM_ASRTGO (SCM_NULLP (args), wrongnumargs);
#ifdef SCM_FLOATS
      if (SCM_SUBRF (proc))
        {
          if (SCM_INUMP (arg1))
            {
              RETURN (scm_makdbl (SCM_DSUBRF (proc) ((double) SCM_INUM (arg1)), 0.0));
            }
          SCM_ASRTGO (SCM_NIMP (arg1), floerr);
          if (SCM_REALP (arg1))
            {
              RETURN (scm_makdbl (SCM_DSUBRF (proc) (SCM_REALPART (arg1)), 0.0));
            }
#ifdef SCM_BIGDIG
          if SCM_BIGP
            (arg1)
              RETURN (scm_makdbl (SCM_DSUBRF (proc) (scm_big2dbl (arg1)), 0.0))
#endif
        floerr:
          scm_wta (arg1, (char *) SCM_ARG1, SCM_CHARS (SCM_SNAME (proc)));
        }
#endif
      proc = (SCM) SCM_SNAME (proc);
      {
        char *chrs = SCM_CHARS (proc) + SCM_LENGTH (proc) - 1;
        while ('c' != *--chrs)
          {
            SCM_ASSERT (SCM_NIMP (arg1) && SCM_CONSP (arg1),
                    arg1, SCM_ARG1, SCM_CHARS (proc));
            arg1 = ('a' == *chrs) ? SCM_CAR (arg1) : SCM_CDR (arg1);
          }
        RETURN (arg1)
      }
    case scm_tc7_subr_3:
      RETURN (SCM_SUBRF (proc) (arg1, SCM_CAR (args), SCM_CAR (SCM_CDR (args))))
    case scm_tc7_lsubr:
#ifdef DEVAL
      RETURN (SCM_SUBRF (proc) (SCM_UNBNDP (arg1) ? SCM_EOL : debug.vect[0].a.args))
#else
      RETURN (SCM_SUBRF (proc) (SCM_UNBNDP (arg1) ? SCM_EOL : scm_cons (arg1, args)))
#endif
    case scm_tc7_lsubr_2:
      SCM_ASRTGO (SCM_NIMP (args) && SCM_CONSP (args), wrongnumargs);
      RETURN (SCM_SUBRF (proc) (arg1, SCM_CAR (args), SCM_CDR (args)))
    case scm_tc7_asubr:
      if (SCM_NULLP (args))
        RETURN (SCM_SUBRF (proc) (arg1, SCM_UNDEFINED))
      while (SCM_NIMP (args))
        {
          SCM_ASSERT (SCM_CONSP (args), args, SCM_ARG2, "apply");
          arg1 = SCM_SUBRF (proc) (arg1, SCM_CAR (args));
          args = SCM_CDR (args);
        }
      RETURN (arg1);
    case scm_tc7_rpsubr:
      if (SCM_NULLP (args))
        RETURN (SCM_BOOL_T);
      while (SCM_NIMP (args))
        {
          SCM_ASSERT (SCM_CONSP (args), args, SCM_ARG2, "apply");
          if (SCM_FALSEP (SCM_SUBRF (proc) (arg1, SCM_CAR (args))))
            RETURN (SCM_BOOL_F);
          arg1 = SCM_CAR (args);
          args = SCM_CDR (args);
        }
      RETURN (SCM_BOOL_T);
    case scm_tcs_closures:
#ifdef DEVAL
      arg1 = (SCM_UNBNDP (arg1) ? SCM_EOL : debug.vect[0].a.args);
#else
      arg1 = (SCM_UNBNDP (arg1) ? SCM_EOL : scm_cons (arg1, args));
#endif
#ifndef RECKLESS
      if (scm_badargsp (SCM_CAR (SCM_CODE (proc)), arg1))
        goto wrongnumargs;
#endif
      args = EXTEND_ENV (SCM_CAR (SCM_CODE (proc)), arg1, SCM_ENV (proc));
      proc = SCM_CODE (proc);
      while (SCM_NNULLP (proc = SCM_CDR (proc)))
        arg1 = EVALCAR (proc, args);
      RETURN (arg1);
    case scm_tc7_contin:
      SCM_ASRTGO (SCM_NULLP (args), wrongnumargs);
      scm_call_continuation (proc, arg1);
#ifdef CCLO
    case scm_tc7_cclo:
#ifdef DEVAL
      args = (SCM_UNBNDP(arg1) ? SCM_EOL : debug.vect[0].a.args);
      arg1 = proc;
      proc = SCM_CCLO_SUBR (proc);
      debug.vect[0].a.proc = proc;
      debug.vect[0].a.args = scm_cons (arg1, args);
#else
      args = (SCM_UNBNDP(arg1) ? SCM_EOL : scm_cons (arg1, args));
      arg1 = proc;
      proc = SCM_CCLO_SUBR (proc);
#endif
      goto tail;
#endif
    wrongnumargs:
      scm_wrong_num_args (proc);
    default:
    badproc:
      scm_wta (proc, (char *) SCM_ARG1, "apply");
      RETURN (arg1);
    }
#ifdef DEVAL
exit:
  if (CHECK_EXIT)
    if (SCM_EXIT_FRAME_P || (SCM_TRACE_P && SCM_TRACED_FRAME_P (debug)))
      {
        SCM_EXIT_FRAME_P = 0;
        SCM_RESET_DEBUG_MODE;
        SCM_CLEAR_TRACED_FRAME (debug);
        if (SCM_CHEAPTRAPS_P)
          arg1 = scm_make_debugobj ((scm_debug_frame *) &debug);
        else
          {
            scm_make_cont (&arg1);
            if (setjmp (SCM_JMPBUF (arg1)))
              {
                proc = SCM_THROW_VALUE (arg1);
                goto ret;
              }
          }
        scm_ithrow (scm_i_exit_frame, scm_cons2 (arg1, proc, SCM_EOL), 0);
      }
ret:
  scm_last_debug_frame = debug.prev;
  return proc;
#endif
}


/* SECTION: The rest of this file is only read once.
 */

#ifndef DEVAL

SCM_PROC(s_map, "map", 2, 0, 1, scm_map);

SCM 
scm_map (proc, arg1, args)
     SCM proc;
     SCM arg1;
     SCM args;
{
  long i;
  SCM res = SCM_EOL;
  SCM *pres = &res;
  SCM *ve = &args;              /* Keep args from being optimized away. */

  if (SCM_NULLP (arg1))
    return res;
  SCM_ASSERT (SCM_NIMP (arg1), arg1, SCM_ARG2, s_map);
  if (SCM_NULLP (args))
    {
      while (SCM_NIMP (arg1))
        {
          SCM_ASSERT (SCM_CONSP (arg1), arg1, SCM_ARG2, s_map);
          *pres = scm_cons (scm_apply (proc, SCM_CAR (arg1), scm_listofnull), SCM_EOL);
          pres = SCM_CDRLOC (*pres);
          arg1 = SCM_CDR (arg1);
        }
      return res;
    }
  args = scm_vector (scm_cons (arg1, args));
  ve = SCM_VELTS (args);
#ifndef RECKLESS
  for (i = SCM_LENGTH (args) - 1; i >= 0; i--)
    SCM_ASSERT (SCM_NIMP (ve[i]) && SCM_CONSP (ve[i]), args, SCM_ARG2, s_map);
#endif
  while (1)
    {
      arg1 = SCM_EOL;
      for (i = SCM_LENGTH (args) - 1; i >= 0; i--)
        {
          if SCM_IMP
            (ve[i]) return res;
          arg1 = scm_cons (SCM_CAR (ve[i]), arg1);
          ve[i] = SCM_CDR (ve[i]);
        }
      *pres = scm_cons (scm_apply (proc, arg1, SCM_EOL), SCM_EOL);
      pres = SCM_CDRLOC (*pres);
    }
}


SCM_PROC(s_for_each, "for-each", 2, 0, 1, scm_for_each);

SCM 
scm_for_each (proc, arg1, args)
     SCM proc;
     SCM arg1;
     SCM args;
{
  SCM *ve = &args;              /* Keep args from being optimized away. */
  long i;
  if SCM_NULLP (arg1)
    return SCM_UNSPECIFIED;
  SCM_ASSERT (SCM_NIMP (arg1), arg1, SCM_ARG2, s_for_each);
  if SCM_NULLP (args)
    {
      while SCM_NIMP (arg1)
        {
          SCM_ASSERT (SCM_CONSP (arg1), arg1, SCM_ARG2, s_for_each);
          scm_apply (proc, SCM_CAR (arg1), scm_listofnull);
          arg1 = SCM_CDR (arg1);
        }
      return SCM_UNSPECIFIED;
    }
  args = scm_vector (scm_cons (arg1, args));
  ve = SCM_VELTS (args);
#ifndef RECKLESS
  for (i = SCM_LENGTH (args) - 1; i >= 0; i--)
    SCM_ASSERT (SCM_NIMP (ve[i]) && SCM_CONSP (ve[i]), args, SCM_ARG2, s_for_each);
#endif
  while (1)
    {
      arg1 = SCM_EOL;
      for (i = SCM_LENGTH (args) - 1; i >= 0; i--)
        {
          if SCM_IMP
            (ve[i]) return SCM_UNSPECIFIED;
          arg1 = scm_cons (SCM_CAR (ve[i]), arg1);
          ve[i] = SCM_CDR (ve[i]);
        }
      scm_apply (proc, arg1, SCM_EOL);
    }
}



SCM 
scm_closure (code, env)
     SCM code;
     SCM env;
{
  register SCM z;
  SCM_NEWCELL (z);
  SCM_SETCODE (z, code);
  SCM_SETENV (z, env);
  return z;
}


long scm_tc16_promise;

SCM 
scm_makprom (code)
     SCM code;
{
  register SCM z;
  SCM_NEWCELL (z);
  SCM_SETCDR (z, code);
  SCM_SETCAR (z, scm_tc16_promise);
  return z;
}



static int  prinprom SCM_P ((SCM exp, SCM port, scm_print_state *pstate));

static int 
prinprom (exp, port, pstate)
     SCM exp;
     SCM port;
     scm_print_state *pstate;
{
  int writingp = SCM_WRITINGP (pstate);
  scm_gen_puts (scm_regular_string, "#<promise ", port);
  SCM_SET_WRITINGP (pstate, 1);
  scm_iprin1 (SCM_CDR (exp), port, pstate);
  SCM_SET_WRITINGP (pstate, writingp);
  scm_gen_putc ('>', port);
  return !0;
}


SCM_PROC(s_makacro, "procedure->syntax", 1, 0, 0, scm_makacro);

SCM 
scm_makacro (code)
     SCM code;
{
  register SCM z;
  SCM_NEWCELL (z);
  SCM_SETCDR (z, code);
  SCM_SETCAR (z, scm_tc16_macro);
  return z;
}


SCM_PROC(s_makmacro, "procedure->macro", 1, 0, 0, scm_makmacro);

SCM 
scm_makmacro (code)
     SCM code;
{
  register SCM z;
  SCM_NEWCELL (z);
  SCM_SETCDR (z, code);
  SCM_SETCAR (z, scm_tc16_macro | (1L << 16));
  return z;
}


SCM_PROC(s_makmmacro, "procedure->memoizing-macro", 1, 0, 0, scm_makmmacro);

SCM 
scm_makmmacro (code)
     SCM code;
{
  register SCM z;
  SCM_NEWCELL (z);
  SCM_SETCDR (z, code);
  SCM_SETCAR (z, scm_tc16_macro | (2L << 16));
  return z;
}



static int  prinmacro SCM_P ((SCM exp, SCM port, scm_print_state *pstate));

static int 
prinmacro (exp, port, pstate)
     SCM exp;
     SCM port;
     scm_print_state *pstate;
{
  int writingp = SCM_WRITINGP (pstate);
  if (SCM_CAR (exp) & (3L << 16))
    scm_gen_puts (scm_regular_string, "#<macro", port);
  else
    scm_gen_puts (scm_regular_string, "#<syntax", port);
  if (SCM_CAR (exp) & (2L << 16))
    scm_gen_putc ('!', port);
  scm_gen_putc (' ', port);
  SCM_SET_WRITINGP (pstate, 1);
  scm_iprin1 (SCM_CDR (exp), port, pstate);
  SCM_SET_WRITINGP (pstate, writingp);
  scm_gen_putc ('>', port);
  return !0;
}

SCM_PROC(s_force, "force", 1, 0, 0, scm_force);

SCM 
scm_force (x)
     SCM x;
{
  SCM_ASSERT ((SCM_TYP16 (x) == scm_tc16_promise), x, SCM_ARG1, s_force);
  if (!((1L << 16) & SCM_CAR (x)))
    {
      SCM ans = scm_apply (SCM_CDR (x), SCM_EOL, SCM_EOL);
      if (!((1L << 16) & SCM_CAR (x)))
        {
          SCM_DEFER_INTS;
          SCM_SETCDR (x, ans);
          SCM_SETOR_CAR (x, (1L << 16));
          SCM_ALLOW_INTS;
        }
    }
  return SCM_CDR (x);
}

SCM_PROC (s_promise_p, "promise?", 1, 0, 0, scm_promise_p);

SCM
scm_promise_p (x)
     SCM x;
{
  return ((SCM_NIMP (x) && (SCM_TYP16 (x) == scm_tc16_promise))
           ? SCM_BOOL_T
           : SCM_BOOL_F);
}

SCM_PROC(s_copy_tree, "copy-tree", 1, 0, 0, scm_copy_tree);

SCM 
scm_copy_tree (obj)
     SCM obj;
{
  SCM ans, tl;
  if SCM_IMP
    (obj) return obj;
  if (SCM_VECTORP (obj))
    {
      scm_sizet i = SCM_LENGTH (obj);
      ans = scm_make_vector (SCM_MAKINUM (i), SCM_UNSPECIFIED, SCM_UNDEFINED);
      while (i--)
        SCM_VELTS (ans)[i] = scm_copy_tree (SCM_VELTS (obj)[i]);
      return ans;
    }
  if SCM_NCONSP (obj)
    return obj;
/*  return scm_cons(scm_copy_tree(SCM_CAR(obj)), scm_copy_tree(SCM_CDR(obj))); */
  ans = tl = scm_cons (scm_copy_tree (SCM_CAR (obj)), SCM_UNSPECIFIED);
  while (SCM_NIMP (obj = SCM_CDR (obj)) && SCM_CONSP (obj))
    {
      SCM_SETCDR (tl, scm_cons (scm_copy_tree (SCM_CAR (obj)),
                                SCM_UNSPECIFIED));
      tl = SCM_CDR (tl);
    }
  SCM_SETCDR (tl, obj);
  return ans;
}


SCM 
scm_eval_3 (obj, copyp, env)
     SCM obj;
     int copyp;
     SCM env;
{
  if (SCM_NIMP (SCM_CDR (scm_system_transformer)))
    obj = scm_apply (SCM_CDR (scm_system_transformer), obj, scm_listofnull);
  else if (copyp)
    obj = scm_copy_tree (obj);
  return XEVAL (obj, env);
}


SCM
scm_top_level_env (thunk)
     SCM thunk;
{
  if (SCM_IMP(thunk))
    return SCM_EOL;
  else
    return scm_cons(thunk, (SCM)SCM_EOL);
}

SCM_PROC(s_eval2, "eval2", 2, 0, 0, scm_eval2);

SCM
scm_eval2 (obj, env_thunk)
     SCM obj;
     SCM env_thunk;
{
  return scm_eval_3 (obj, 1, scm_top_level_env(env_thunk));
}

SCM_PROC(s_eval, "eval", 1, 0, 0, scm_eval);

SCM
scm_eval (obj)
     SCM obj;
{
  return
    scm_eval_3(obj, 1, scm_top_level_env(SCM_CDR(scm_top_level_lookup_thunk_var)));
}

SCM_PROC(s_eval_x, "eval!", 1, 0, 0, scm_eval_x);

SCM
scm_eval_x (obj)
     SCM obj;
{
  return
    scm_eval_3(obj,
               0,
               scm_top_level_env (SCM_CDR (scm_top_level_lookup_thunk_var)));
}

SCM_PROC (s_macro_eval_x, "macro-eval!", 2, 0, 0, scm_macro_eval_x);

SCM
scm_macro_eval_x (exp, env)
     SCM exp;
     SCM env;
{
  return scm_eval_3 (exp, 0, env);
}


SCM 
scm_definedp (x, env)
     SCM x;
     SCM env;
{
  SCM proc = SCM_CAR (x = SCM_CDR (x));
  if (SCM_ISYMP (proc))
    return SCM_BOOL_T;
  else if(SCM_IMP(proc) || !SCM_SYMBOLP(proc))
    return SCM_BOOL_F;
  else
    {
      SCM vcell = scm_sym2vcell(proc, env_top_level(env), SCM_BOOL_F);
      return (vcell == SCM_BOOL_F || SCM_UNBNDP(SCM_CDR(vcell))) ? SCM_BOOL_F : SCM_BOOL_T;
    }
}

static scm_smobfuns promsmob =
{scm_markcdr, scm_free0, prinprom};

static scm_smobfuns macrosmob =
{scm_markcdr, scm_free0, prinmacro};


SCM 
scm_make_synt (name, macroizer, fcn)
     char *name;
     SCM (*macroizer) ();
     SCM (*fcn) ();
{
  SCM symcell = scm_sysintern (name, SCM_UNDEFINED);
  long tmp = ((((SCM_CELLPTR) (SCM_CAR (symcell))) - scm_heap_org) << 8);
  register SCM z;
  if ((tmp >> 8) != ((SCM_CELLPTR) (SCM_CAR (symcell)) - scm_heap_org))
    tmp = 0;
  SCM_NEWCELL (z);
  SCM_SUBRF (z) = fcn;
  SCM_SETCAR (z, tmp + scm_tc7_subr_2);
  SCM_SETCDR (symcell, macroizer (z));
  return SCM_CAR (symcell);
}


/* At this point, scm_deval and scm_dapply are generated.
 */

#ifdef DEBUG_EXTENSIONS
# define DEVAL
# include "eval.c"
#endif



void 
scm_init_eval ()
{
  scm_tc16_promise = scm_newsmob (&promsmob);
  scm_tc16_macro = scm_newsmob (&macrosmob);
  scm_i_apply = scm_make_subr ("apply", scm_tc7_lsubr_2, scm_apply);
  scm_system_transformer = scm_sysintern ("scm:eval-transformer", SCM_UNDEFINED);
  scm_i_dot = SCM_CAR (scm_sysintern (".", SCM_UNDEFINED));
  scm_i_arrow = SCM_CAR (scm_sysintern ("=>", SCM_UNDEFINED));
  scm_i_else = SCM_CAR (scm_sysintern ("else", SCM_UNDEFINED));
  scm_i_unquote = SCM_CAR (scm_sysintern ("unquote", SCM_UNDEFINED));
  scm_i_uq_splicing = SCM_CAR (scm_sysintern ("unquote-splicing", SCM_UNDEFINED));

  /* acros */
  scm_i_quasiquote = scm_make_synt (s_quasiquote, scm_makacro, scm_m_quasiquote);
  scm_make_synt (s_undefine, scm_makacro, scm_m_undefine);
  scm_make_synt (s_delay, scm_makacro, scm_m_delay);
  /* end of acros */

  scm_top_level_lookup_thunk_var =
    scm_sysintern("*top-level-lookup-thunk*", SCM_BOOL_F);

  scm_i_and = scm_make_synt ("and", scm_makmmacro, scm_m_and);
  scm_i_begin = scm_make_synt ("begin", scm_makmmacro, scm_m_begin);
  scm_i_case = scm_make_synt ("case", scm_makmmacro, scm_m_case);
  scm_i_cond = scm_make_synt ("cond", scm_makmmacro, scm_m_cond);
  scm_i_define = scm_make_synt ("define", scm_makmmacro, scm_m_define);
  scm_i_do = scm_make_synt ("do", scm_makmmacro, scm_m_do);
  scm_i_if = scm_make_synt ("if", scm_makmmacro, scm_m_if);
  scm_i_lambda = scm_make_synt ("lambda", scm_makmmacro, scm_m_lambda);
  scm_i_let = scm_make_synt ("let", scm_makmmacro, scm_m_let);
  scm_i_letrec = scm_make_synt ("letrec", scm_makmmacro, scm_m_letrec);
  scm_i_letstar = scm_make_synt ("let*", scm_makmmacro, scm_m_letstar);
  scm_i_or = scm_make_synt ("or", scm_makmmacro, scm_m_or);
  scm_i_quote = scm_make_synt ("quote", scm_makmmacro, scm_m_quote);
  scm_i_set = scm_make_synt ("set!", scm_makmmacro, scm_m_set);
  scm_i_atapply = scm_make_synt ("@apply", scm_makmmacro, scm_m_apply);
  scm_i_atcall_cc = scm_make_synt ("@call-with-current-continuation",
                                   scm_makmmacro, scm_m_cont);

  scm_make_synt ("defined?", scm_makmmacro, scm_definedp);

#ifdef DEBUG_EXTENSIONS
  scm_i_enter_frame = SCM_CAR (scm_sysintern ("enter-frame", SCM_UNDEFINED));
  scm_i_apply_frame = SCM_CAR (scm_sysintern ("apply-frame", SCM_UNDEFINED));
  scm_i_exit_frame = SCM_CAR (scm_sysintern ("exit-frame", SCM_UNDEFINED));
  scm_i_trace = SCM_CAR (scm_sysintern ("trace", SCM_UNDEFINED));
#endif

#include "eval.x"
}

#endif /* !DEVAL */