libguile/lang.c

   1 /*      Copyright (C) 1999, 2000, 2001 Free Software Foundation, Inc.
   2  *
   3  * This program is free software; you can redistribute it and/or modify
   4  * it under the terms of the GNU General Public License as published by
   5  * the Free Software Foundation; either version 2, or (at your option)
   6  * any later version.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License
  14  * along with this software; see the file COPYING.  If not, write to
  15  * the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  16  * Boston, MA 02111-1307 USA
  17  *
  18  * As a special exception, the Free Software Foundation gives permission
  19  * for additional uses of the text contained in its release of GUILE.
  20  *
  21  * The exception is that, if you link the GUILE library with other files
  22  * to produce an executable, this does not by itself cause the
  23  * resulting executable to be covered by the GNU General Public License.
  24  * Your use of that executable is in no way restricted on account of
  25  * linking the GUILE library code into it.
  26  *
  27  * This exception does not however invalidate any other reasons why
  28  * the executable file might be covered by the GNU General Public License.
  29  *
  30  * This exception applies only to the code released by the
  31  * Free Software Foundation under the name GUILE.  If you copy
  32  * code from other Free Software Foundation releases into a copy of
  33  * GUILE, as the General Public License permits, the exception does
  34  * not apply to the code that you add in this way.  To avoid misleading
  35  * anyone as to the status of such modified files, you must delete
  36  * this exception notice from them.
  37  *
  38  * If you write modifications of your own for GUILE, it is your choice
  39  * whether to permit this exception to apply to your modifications.
  40  * If you do not wish that, delete this exception notice.  */
  41
  42
  43 \f
  44
  45 #include "libguile/_scm.h"
  46
  47 #include "libguile/eval.h"
  48 #include "libguile/macros.h"
  49 #include "libguile/root.h"
  50
  51 #include "libguile/validate.h"
  52 #include "libguile/lang.h"
  53
  54 \f
  55
  56 /* {Multi-language support}
  57  */
  58
  59 /* Representation of pairs:
  60  *
  61  * Since we're going to share data with Scheme, we use EOL instead of nil
  62  * in all data structures.
  63  */
  64
  65 #ifdef SCM_ENABLE_ELISP
  66 #if 0
  67
  68 SCM_DEFINE (scm_nil_cons, "nil-cons", 2, 0, 0,
  69             (SCM x, SCM y),
  70             "Create a new cons cell with @var{x} as the car and @var{y} as\n"
  71             "the cdr, but convert @var{y} to Scheme's end-of-list if it is\n"
  72             "a LISP nil.")
  73 #define FUNC_NAME s_scm_nil_cons
  74 {
  75   return scm_cons (x, SCM_NIL2EOL (y, y));
  76 }
  77 #undef FUNC_NAME
  78
  79
  80 SCM_DEFINE (scm_nil_car, "nil-car", 1, 0, 0,
  81             (SCM x),
  82             "Return the car of @var{x}, but convert it to LISP nil if it\n"
  83             "is Scheme's end-of-list.")
  84 #define FUNC_NAME s_scm_nil_car
  85 {
  86   if (SCM_NILP (x))
  87     return scm_lisp_nil;
  88   SCM_VALIDATE_CONS (1,x);
  89   return SCM_CAR (x);
  90 }
  91 #undef FUNC_NAME
  92
  93 SCM_DEFINE (scm_nil_cdr, "nil-cdr", 1, 0, 0,
  94             (SCM x),
  95             "Return the cdr of @var{x}, but convert it to LISP nil if it\n"
  96             "is Scheme's end-of-list.")
  97 #define FUNC_NAME s_scm_nil_cdr
  98 {
  99   if (SCM_NILP (x))
 100     return scm_lisp_nil;
 101   SCM_VALIDATE_CONS (1,x);
 102   return SCM_EOL2NIL (SCM_CDR (x), x);
 103 }
 104 #undef FUNC_NAME
 105
 106 /* GJB:FIXME:: why does this return scm_lisp_nil instead of SCM_BOOL_F?
 107    Could use SCM_BOOL, below, otherwise */
 108 SCM_DEFINE (scm_null, "null", 1, 0, 0,
 109             (SCM x),
 110             "Return LISP's @code{t} if @var{x} is nil in the LISP sense,\n"
 111             "return LISP's nil otherwise.")
 112 #define FUNC_NAME s_scm_null
 113 {
 114   return (SCM_NILP (x) || SCM_NULLP (x) || SCM_FALSEP (x)) ? scm_lisp_t : scm_lisp_nil;
 115 }
 116 #undef FUNC_NAME
 117
 118 SCM
 119 scm_m_while (SCM exp, SCM env)
 120 {
 121   register SCM x = exp = SCM_CDR (exp);
 122   SCM z = scm_eval_car (x, env);
 123   while (!SCM_NILP (z) && SCM_NFALSEP (z))
 124     {
 125       while (SCM_NNULLP (x = SCM_CDR (x)))
 126         {
 127           if (SCM_NIMP (SCM_CAR (x)))
 128             (*scm_ceval_ptr) (SCM_CAR (x), env);
 129         }
 130       z = scm_eval_car (x = exp, env);
 131     }
 132   return scm_lisp_nil;
 133 }
 134
 135 /* GJB:FIXME:: why does this return scm_lisp_nil instead of SCM_BOOL_F?
 136    Could use SCM_BOOL, below, otherwise */
 137 SCM_DEFINE1 (scm_nil_eq, "nil-eq", scm_tc7_rpsubr,
 138              (SCM x, SCM y),
 139              "Compare @var{x} and @var{y} and return LISP's t if they are\n"
 140              "@code{eq?}, return LISP's nil otherwise.")
 141 #define FUNC_NAME s_scm_nil_eq
 142 {
 143   return ((SCM_EQ_P (x, y)
 144            || (SCM_NILP (x) && (SCM_NULLP (y) || SCM_FALSEP (y)))
 145            || (SCM_NILP (y) && (SCM_NULLP (x) || SCM_FALSEP (x))))
 146           ? scm_lisp_t
 147           : scm_lisp_nil);
 148 }
 149 #undef FUNC_NAME
 150
 151 #endif /* 0 */
 152 \f
 153
 154 void
 155 scm_init_lang ()
 156 {
 157 #if 0
 158 #ifndef SCM_MAGIC_SNARFER
 159 #include "libguile/lang.x"
 160 #endif
 161   scm_make_synt ("nil-while", scm_makacro, scm_m_while);
 162 #endif
 163
 164   scm_c_define ("%nil", SCM_ELISP_NIL);
 165 }
 166
 167 #endif /* SCM_ENABLE_ELISP */
 168
 169 /*
 170   Local Variables:
 171   c-file-style: "gnu"
 172   End:
 173 */