libguile/dynwind.c

   1 /*      Copyright (C) 1995,1996 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, 675 Mass Ave, Cambridge, MA 02139, USA.
  16  *
  17  * As a special exception, the Free Software Foundation gives permission
  18  * for additional uses of the text contained in its release of GUILE.
  19  *
  20  * The exception is that, if you link the GUILE library with other files
  21  * to produce an executable, this does not by itself cause the
  22  * resulting executable to be covered by the GNU General Public License.
  23  * Your use of that executable is in no way restricted on account of
  24  * linking the GUILE library code into it.
  25  *
  26  * This exception does not however invalidate any other reasons why
  27  * the executable file might be covered by the GNU General Public License.
  28  *
  29  * This exception applies only to the code released by the
  30  * Free Software Foundation under the name GUILE.  If you copy
  31  * code from other Free Software Foundation releases into a copy of
  32  * GUILE, as the General Public License permits, the exception does
  33  * not apply to the code that you add in this way.  To avoid misleading
  34  * anyone as to the status of such modified files, you must delete
  35  * this exception notice from them.
  36  *
  37  * If you write modifications of your own for GUILE, it is your choice
  38  * whether to permit this exception to apply to your modifications.
  39  * If you do not wish that, delete this exception notice.
  40  */
  41 \f
  42
  43 #include <stdio.h>
  44 #include "_scm.h"
  45 #include "eval.h"
  46 #include "alist.h"
  47
  48 #include "dynwind.h"
  49 \f
  50
  51 /* {Dynamic wind}
  52  */
  53
  54
  55
  56 SCM_PROC(s_dynamic_wind, "dynamic-wind", 3, 0, 0, scm_dynamic_wind);
  57
  58 SCM
  59 scm_dynamic_wind (thunk1, thunk2, thunk3)
  60      SCM thunk1;
  61      SCM thunk2;
  62      SCM thunk3;
  63 {
  64   SCM ans;
  65   scm_apply (thunk1, SCM_EOL, SCM_EOL);
  66   scm_dynwinds = scm_acons (thunk1, thunk3, scm_dynwinds);
  67   ans = scm_apply (thunk2, SCM_EOL, SCM_EOL);
  68   scm_dynwinds = SCM_CDR (scm_dynwinds);
  69   scm_apply (thunk3, SCM_EOL, SCM_EOL);
  70   return ans;
  71 }
  72
  73
  74 void
  75 scm_dowinds (to, delta)
  76      SCM to;
  77      long delta;
  78 {
  79  tail:
  80   if (scm_dynwinds == to);
  81   else if (0 > delta)
  82     {
  83       SCM wind_elt;
  84       SCM wind_key;
  85
  86       scm_dowinds (SCM_CDR (to), 1 + delta);
  87       wind_elt = SCM_CAR (to);
  88 #if 0
  89       if (SCM_INUMP (wind_elt))
  90         {
  91           scm_cross_dynwind_binding_scope (wind_elt, 0);
  92         }
  93       else
  94 #endif
  95         {
  96           wind_key = SCM_CAR (wind_elt);
  97           if (   !(SCM_NIMP (wind_key) && SCM_SYMBOLP (wind_key))
  98               && (wind_key != SCM_BOOL_F)
  99               && (wind_key != SCM_BOOL_T))
 100             scm_apply (wind_key, SCM_EOL, SCM_EOL);
 101         }
 102       scm_dynwinds = to;
 103     }
 104   else
 105     {
 106       SCM from;
 107       SCM wind_elt;
 108       SCM wind_key;
 109
 110       from = SCM_CDR (SCM_CAR (scm_dynwinds));
 111       wind_elt = SCM_CAR (scm_dynwinds);
 112       scm_dynwinds = SCM_CDR (scm_dynwinds);
 113 #if 0
 114       if (SCM_INUMP (wind_elt))
 115         {
 116           scm_cross_dynwind_binding_scope (wind_elt, 0);
 117         }
 118       else
 119 #endif
 120         {
 121           wind_key = SCM_CAR (wind_elt);
 122           if (   !(SCM_NIMP (wind_key) && SCM_SYMBOLP (wind_key))
 123               && (wind_key != SCM_BOOL_F)
 124               && (wind_key != SCM_BOOL_T))
 125             scm_apply (from, SCM_EOL, SCM_EOL);
 126         }
 127       delta--;
 128       goto tail;                /* scm_dowinds(to, delta-1); */
 129     }
 130 }
 131
 132
 133
 134 void
 135 scm_init_dynwind ()
 136 {
 137 #include "dynwind.x"
 138 }
 139