syntax.c 78.5 KB
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/* GNU Emacs routines to deal with syntax tables; also word and list parsing.
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   Copyright (C) 1985, 87, 93, 94, 95, 1997 Free Software Foundation, Inc.
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This file is part of GNU Emacs.

GNU Emacs is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.

GNU Emacs 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 GNU Emacs; see the file COPYING.  If not, write to
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the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */
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#include <config.h>
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#include <ctype.h>
#include "lisp.h"
#include "commands.h"
#include "buffer.h"
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#include "charset.h"
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/* Make syntax table lookup grant data in gl_state.  */
#define SYNTAX_ENTRY_VIA_PROPERTY

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#include "syntax.h"
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#include "intervals.h"

/* We use these constants in place for comment-style and
   string-ender-char to distinguish  comments/strings started by
   comment_fence and string_fence codes.  */

#define ST_COMMENT_STYLE (256 + 1)
#define ST_STRING_STYLE (256 + 2)
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#include "category.h"
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Lisp_Object Qsyntax_table_p, Qsyntax_table, Qscan_error;
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static void scan_sexps_forward ();
static int char_quoted ();

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int words_include_escapes;
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int parse_sexp_lookup_properties;
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/* Used as a temporary in SYNTAX_ENTRY and other macros in syntax.h,
   if not compiled with GCC.  No need to mark it, since it is used
   only very temporarily.  */
Lisp_Object syntax_temp;

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/* This is the internal form of the parse state used in parse-partial-sexp.  */

struct lisp_parse_state
  {
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    int depth;		/* Depth at end of parsing.  */
    int instring;	/* -1 if not within string, else desired terminator.  */
    int incomment;	/* Nonzero if within a comment at end of parsing.  */
    int comstyle;	/* comment style a=0, or b=1, or ST_COMMENT_STYLE.  */
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    int quoted;		/* Nonzero if just after an escape char at end of parsing */
    int thislevelstart;	/* Char number of most recent start-of-expression at current level */
    int prevlevelstart; /* Char number of start of containing expression */
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    int location;	/* Char number at which parsing stopped.  */
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    int mindepth;	/* Minimum depth seen while scanning.  */
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    int comstr_start;	/* Position just after last comment/string starter.  */
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  };

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/* These variables are a cache for finding the start of a defun.
   find_start_pos is the place for which the defun start was found.
   find_start_value is the defun start position found for it.
   find_start_buffer is the buffer it was found in.
   find_start_begv is the BEGV value when it was found.
   find_start_modiff is the value of MODIFF when it was found.  */

static int find_start_pos;
static int find_start_value;
static struct buffer *find_start_buffer;
static int find_start_begv;
static int find_start_modiff;
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struct gl_state_s gl_state;		/* Global state of syntax parser.  */

INTERVAL interval_of ();
#define INTERVALS_AT_ONCE 10		/* 1 + max-number of intervals
					   to scan to property-change.  */

/* 
   Update gl_state to an appropriate interval which contains POS.  The
   sign of COUNT give the relative position of POS wrt the previously
   valid interval.  If INIT, only [be]_property fields of gl_state are
   valid at start, the  rest is filled basing on OBJECT.

   `gl_state.*_i' are the intervals, and pos is further in the search
   direction than the intervals - or in an interval.  We update the
   current syntax-table basing on the property of this interval, and
   update the interval to start further than POS - or be
   NULL_INTERVAL.  We also update lim_property to be the next value of
   pos to call this subroutine again - or be before/after the
   start/end of OBJECT.  */

void
update_syntax_table (pos, count, init, object)
     int pos, count, init;
     Lisp_Object object;
{
  Lisp_Object tmp_table;
  int cnt = 0, doing_extra = 0, invalidate = 1;
  INTERVAL i, oldi;

  if (init)
    {
      gl_state.start = gl_state.b_property;
      gl_state.stop = gl_state.e_property;
      gl_state.forward_i = interval_of (pos, object);
      i = gl_state.backward_i = gl_state.forward_i;
      gl_state.left_ok = gl_state.right_ok = 1;
      invalidate = 0;
      if (NULL_INTERVAL_P (i))
	return;
      gl_state.b_property = i->position - 1;
      gl_state.e_property = INTERVAL_LAST_POS (i);
      goto update;
    }
  oldi = i = count > 0 ? gl_state.forward_i : gl_state.backward_i;

  /* We are guarantied to be called with pos either in i, of further off.  */
  if (NULL_INTERVAL_P (i))
    error ("Error in syntax_table logic for to-the-end intervals");
  else if (pos < i->position)		/* Move left.  */
    {
      if (count > 0)
	error ("Error in syntax_table logic for intervals <-.");
      /* Update the interval.  */
      i = update_interval (i, pos);
      if (oldi->position != INTERVAL_LAST_POS (i))
	{
	  invalidate = 0;
	  gl_state.right_ok = 1;	/* Invalidate the other end.  */
	  gl_state.forward_i = i;
	  gl_state.e_property = INTERVAL_LAST_POS (i);
	}
    } 
  else if (pos >= INTERVAL_LAST_POS (i)) /* Move right.  */
    {
      if (count < 0)
	error ("Error in syntax_table logic for intervals ->.");
      /* Update the interval.  */
      i = update_interval (i, pos);
      if (i->position != INTERVAL_LAST_POS (oldi))
	{
	  invalidate = 0;
	  gl_state.left_ok = 1;		/* Invalidate the other end.  */
	  gl_state.backward_i = i;
	  gl_state.b_property = i->position - 1;
	}
    }
  else if (count > 0 ? gl_state.right_ok : gl_state.left_ok)
    {
      /* We do not need to recalculate tmp_table.  */
      tmp_table = gl_state.old_prop;
    }

  update:
  tmp_table = textget (i->plist, Qsyntax_table);

  if (invalidate)
    invalidate = !EQ (tmp_table, gl_state.old_prop); /* Need to invalidate? */
      
  if (invalidate)			/* Did not get to adjacent interval.  */
    {					/* with the same table => */
					/* invalidate the old range.  */
      if (count > 0)
	{
	  gl_state.backward_i = i;
	  gl_state.left_ok = 1;		/* Invalidate the other end.  */
	  gl_state.b_property = i->position - 1;
	} 
      else 
	{
	  gl_state.forward_i = i;	
	  gl_state.right_ok = 1;	/* Invalidate the other end.  */
	  gl_state.e_property = INTERVAL_LAST_POS (i);
	}
    }
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  gl_state.current_syntax_table = tmp_table;
  gl_state.old_prop = tmp_table;
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  if (EQ (Fsyntax_table_p (tmp_table), Qt))
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    {
      gl_state.use_global = 0;
    } 
  else if (CONSP (tmp_table))
    {
      gl_state.use_global = 1;
      gl_state.global_code = tmp_table;
    }
  else 
    {
      gl_state.use_global = 0;
      gl_state.current_syntax_table = current_buffer->syntax_table;
    }

  while (!NULL_INTERVAL_P (i))
    {
      if (cnt && !EQ (tmp_table, textget (i->plist, Qsyntax_table)))
	{
	  if (count > 0)
	    gl_state.right_ok = 0;
	  else 
	    gl_state.left_ok = 0;
	  break;	  
	}
      else if (cnt == INTERVALS_AT_ONCE) 
	{
	  if (count > 0)
	    gl_state.right_ok = 1;
	  else 
	    gl_state.left_ok = 1;
	  break;
	}
      cnt++;
      i = count > 0 ? next_interval (i) : previous_interval (i);
    }
  if (NULL_INTERVAL_P (i)) 
    {					/* This property goes to the end.  */
      if (count > 0)
	gl_state.e_property = gl_state.stop;
      else
	gl_state.b_property = gl_state.start;
    } 
  else 
    {
      if (count > 0) 
	{
	  gl_state.e_property = i->position;
	  gl_state.forward_i = i;
	}
      else 
	{
	  gl_state.b_property = i->position + LENGTH (i) - 1;
	  gl_state.backward_i = i;
	}
    }    
}

/* Returns TRUE if char at POS is quoted.
   Global syntax-table data should be set up already to be good at pos
   or after.  On return global syntax data is good for lookup at POS. */

static int
char_quoted (pos)
     register int pos;
{
  register enum syntaxcode code;
  register int beg = BEGV;
  register int quoted = 0;
  int temp_pos = pos;

  DEC_POS (temp_pos);
  while (temp_pos >= beg
	 && ( UPDATE_SYNTAX_TABLE_BACKWARD (temp_pos), 1)
	 && ((code = SYNTAX (FETCH_CHAR (temp_pos))) == Scharquote
	     || code == Sescape))
    {
      temp_pos--, quoted = !quoted;
    }
  UPDATE_SYNTAX_TABLE (pos);
  return quoted;
}

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/* Find a defun-start that is the last one before POS (or nearly the last).
   We record what we find, so that another call in the same area
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   can return the same value right away.  

   There is no promise at which position the global syntax data is
   valid on return from the subroutine, so the caller should explicitly
   update the global data.  */
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static int
find_defun_start (pos)
     int pos;
{
  int tem;
  int shortage;

  /* Use previous finding, if it's valid and applies to this inquiry.  */
  if (current_buffer == find_start_buffer
      /* Reuse the defun-start even if POS is a little farther on.
	 POS might be in the next defun, but that's ok.
	 Our value may not be the best possible, but will still be usable.  */
      && pos <= find_start_pos + 1000
      && pos >= find_start_value
      && BEGV == find_start_begv
      && MODIFF == find_start_modiff)
    return find_start_value;

  /* Back up to start of line.  */
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  tem = scan_buffer ('\n', pos, BEGV, -1, &shortage, 1);
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  /* We optimize syntax-table lookup for rare updates.  Thus we accept
     only those `^\s(' which are good in global _and_ text-property
     syntax-tables.  */
  gl_state.current_syntax_table = current_buffer->syntax_table;
  gl_state.use_global = 0;
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  while (tem > BEGV)
    {
      /* Open-paren at start of line means we found our defun-start.  */
      if (SYNTAX (FETCH_CHAR (tem)) == Sopen)
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	{
	  SETUP_SYNTAX_TABLE (tem + 1, -1);	/* Try again... */
	  if (SYNTAX (FETCH_CHAR (tem)) == Sopen)
	    break;
	  /* Now fallback to the default value.  */
	  gl_state.current_syntax_table = current_buffer->syntax_table;
	  gl_state.use_global = 0;
	}
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      /* Move to beg of previous line.  */
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      tem = scan_buffer ('\n', tem, BEGV, -2, &shortage, 1);
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    }

  /* Record what we found, for the next try.  */
  find_start_value = tem;
  find_start_buffer = current_buffer;
  find_start_modiff = MODIFF;
  find_start_begv = BEGV;
  find_start_pos = pos;

  return find_start_value;
}

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/* Checks whether FROM is at the end of a comment;
   and if so, returns position of the start of the comment.
   But does not move back before STOP.
   Returns -1 if there is no comment ending at FROM.

   Global syntax data remains valid for backward search starting at
   the returned value (or at FROM, if the search was not successful).  */
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static int
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back_comment (from, stop, comstyle)
     int from, stop, comstyle;
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{
  /* Look back, counting the parity of string-quotes,
     and recording the comment-starters seen.
     When we reach a safe place, assume that's not in a string;
     then step the main scan to the earliest comment-starter seen
     an even number of string quotes away from the safe place.

     OFROM[I] is position of the earliest comment-starter seen
     which is I+2X quotes from the comment-end.
     PARITY is current parity of quotes from the comment end.  */
  int parity = 0;
  int my_stringend = 0;
  int string_lossage = 0;
  int comment_end = from;
  int comstart_pos = 0;
  int comstart_parity = 0;
  int scanstart = from - 1;
  register enum syntaxcode code;
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  int c;
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  /* At beginning of range to scan, we're outside of strings;
     that determines quote parity to the comment-end.  */
  while (from != stop)
    {
      /* Move back and examine a character.  */
      DEC_POS (from);
      UPDATE_SYNTAX_TABLE_BACKWARD (from);

      c = FETCH_CHAR (from);
      code = SYNTAX (c);

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      /* If this char is the second of a 2-char comment end sequence,
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	 back up and give the pair the appropriate syntax.  */
      if (from > stop && SYNTAX_COMEND_SECOND (c)
	  && SYNTAX_COMEND_FIRST (FETCH_CHAR (from - 1)))
	{
	  code = Sendcomment;
	  DEC_POS (from);
	  /* This is apparently the best we can do: */
	  UPDATE_SYNTAX_TABLE_BACKWARD (from);
	  c = FETCH_CHAR (from);
	}
			
      /* If this char starts a 2-char comment start sequence,
	 treat it like a 1-char comment starter.  */
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      if (from < scanstart && SYNTAX_COMSTART_FIRST (c)
	  && SYNTAX_COMSTART_SECOND (FETCH_CHAR (from + 1))
	  && comstyle == SYNTAX_COMMENT_STYLE (FETCH_CHAR (from + 1)))
	code = Scomment;
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      /* Ignore escaped characters.  */
      if (char_quoted (from))
	continue;

      /* Track parity of quotes.  */
      if (code == Sstring)
	{
	  parity ^= 1;
	  if (my_stringend == 0)
	    my_stringend = c;
	  /* If we have two kinds of string delimiters.
	     There's no way to grok this scanning backwards.  */
	  else if (my_stringend != c)
	    string_lossage = 1;
	}

      if (code == Sstring_fence || code == Scomment_fence)
	{
	  parity ^= 1;
	  if (my_stringend == 0)
	    my_stringend = 
		code == Sstring_fence ? ST_STRING_STYLE : ST_COMMENT_STYLE;
	  /* If we have two kinds of string delimiters.
	     There's no way to grok this scanning backwards.  */
	  else if (my_stringend != (code == Sstring_fence 
				    ? ST_STRING_STYLE : ST_COMMENT_STYLE))
	    string_lossage = 1;
	}

      /* Record comment-starters according to that
	 quote-parity to the comment-end.  */
      if (code == Scomment)
	{
	  comstart_parity = parity;
	  comstart_pos = from;
	}

      /* If we find another earlier comment-ender,
	 any comment-starts earlier than that don't count
	 (because they go with the earlier comment-ender).  */
      if (code == Sendcomment
	  && SYNTAX_COMMENT_STYLE (FETCH_CHAR (from)) == comstyle)
	break;

      /* Assume a defun-start point is outside of strings.  */
      if (code == Sopen
	  && (from == stop || FETCH_CHAR (from - 1) == '\n'))
	break;
    }

  if (comstart_pos == 0)
    {
      from = comment_end;
      UPDATE_SYNTAX_TABLE_FORWARD (comment_end - 1);
    }
  /* If the earliest comment starter
     is followed by uniform paired string quotes or none,
     we know it can't be inside a string
     since if it were then the comment ender would be inside one.
     So it does start a comment.  Skip back to it.  */
  else if (comstart_parity == 0 && !string_lossage) 
    {
      from = comstart_pos;
      /* Globals are correct now.  */
    }
  else
    {
      /* We had two kinds of string delimiters mixed up
	 together.  Decode this going forwards.
	 Scan fwd from the previous comment ender
	 to the one in question; this records where we
	 last passed a comment starter.  */
      struct lisp_parse_state state;
      scan_sexps_forward (&state, find_defun_start (comment_end),
			  comment_end - 1, -10000, 0, Qnil, 0);
      if (state.incomment)
	{
	  /* scan_sexps_forward changed the direction of search in
	     global variables, so we need to update it completely.  */
	  
	  from = state.comstr_start;
	}
      else
	{
	  from = comment_end;	  
	}
      UPDATE_SYNTAX_TABLE_FORWARD (from - 1);
    }
    
  return from;
}

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DEFUN ("syntax-table-p", Fsyntax_table_p, Ssyntax_table_p, 1, 1, 0,
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  "Return t if OBJECT is a syntax table.\n\
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Currently, any char-table counts as a syntax table.")
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  (object)
     Lisp_Object object;
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{
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  if (CHAR_TABLE_P (object)
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      && EQ (XCHAR_TABLE (object)->purpose, Qsyntax_table))
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    return Qt;
  return Qnil;
}

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static void
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check_syntax_table (obj)
     Lisp_Object obj;
{
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  if (!(CHAR_TABLE_P (obj)
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	&& EQ (XCHAR_TABLE (obj)->purpose, Qsyntax_table)))
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    wrong_type_argument (Qsyntax_table_p, obj);
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}   

DEFUN ("syntax-table", Fsyntax_table, Ssyntax_table, 0, 0, 0,
  "Return the current syntax table.\n\
This is the one specified by the current buffer.")
  ()
{
  return current_buffer->syntax_table;
}

DEFUN ("standard-syntax-table", Fstandard_syntax_table,
   Sstandard_syntax_table, 0, 0, 0,
  "Return the standard syntax table.\n\
This is the one used for new buffers.")
  ()
{
  return Vstandard_syntax_table;
}

DEFUN ("copy-syntax-table", Fcopy_syntax_table, Scopy_syntax_table, 0, 1, 0,
  "Construct a new syntax table and return it.\n\
It is a copy of the TABLE, which defaults to the standard syntax table.")
  (table)
     Lisp_Object table;
{
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  Lisp_Object copy;

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  if (!NILP (table))
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    check_syntax_table (table);
  else
    table = Vstandard_syntax_table;

  copy = Fcopy_sequence (table);
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  /* Only the standard syntax table should have a default element.
     Other syntax tables should inherit from parents instead.  */
  XCHAR_TABLE (copy)->defalt = Qnil;

  /* Copied syntax tables should all have parents.
     If we copied one with no parent, such as the standard syntax table,
     use the standard syntax table as the copy's parent.  */
  if (NILP (XCHAR_TABLE (copy)->parent))
    Fset_char_table_parent (copy, Vstandard_syntax_table);
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  return copy;
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}

DEFUN ("set-syntax-table", Fset_syntax_table, Sset_syntax_table, 1, 1, 0,
  "Select a new syntax table for the current buffer.\n\
One argument, a syntax table.")
  (table)
     Lisp_Object table;
{
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  check_syntax_table (table);
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  current_buffer->syntax_table = table;
  /* Indicate that this buffer now has a specified syntax table.  */
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  current_buffer->local_var_flags
    |= XFASTINT (buffer_local_flags.syntax_table);
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  return table;
}

/* Convert a letter which signifies a syntax code
 into the code it signifies.
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 This is used by modify-syntax-entry, and other things.  */
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unsigned char syntax_spec_code[0400] =
  { 0377, 0377, 0377, 0377, 0377, 0377, 0377, 0377,
    0377, 0377, 0377, 0377, 0377, 0377, 0377, 0377,
    0377, 0377, 0377, 0377, 0377, 0377, 0377, 0377,
    0377, 0377, 0377, 0377, 0377, 0377, 0377, 0377,
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    (char) Swhitespace, (char) Scomment_fence, (char) Sstring, 0377,
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        (char) Smath, 0377, 0377, (char) Squote,
    (char) Sopen, (char) Sclose, 0377, 0377,
	0377, (char) Swhitespace, (char) Spunct, (char) Scharquote,
    0377, 0377, 0377, 0377, 0377, 0377, 0377, 0377,
    0377, 0377, 0377, 0377,
	(char) Scomment, 0377, (char) Sendcomment, 0377,
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    (char) Sinherit, 0377, 0377, 0377, 0377, 0377, 0377, 0377,   /* @, A ... */
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    0377, 0377, 0377, 0377, 0377, 0377, 0377, 0377,
    0377, 0377, 0377, 0377, 0377, 0377, 0377, (char) Sword,
    0377, 0377, 0377, 0377, (char) Sescape, 0377, 0377, (char) Ssymbol,
    0377, 0377, 0377, 0377, 0377, 0377, 0377, 0377,   /* `, a, ... */
    0377, 0377, 0377, 0377, 0377, 0377, 0377, 0377,
    0377, 0377, 0377, 0377, 0377, 0377, 0377, (char) Sword,
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    0377, 0377, 0377, 0377, (char) Sstring_fence, 0377, 0377, 0377
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  };

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/* Indexed by syntax code, give the letter that describes it.  */
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char syntax_code_spec[16] =
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  {
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    ' ', '.', 'w', '_', '(', ')', '\'', '\"', '$', '\\', '/', '<', '>', '@',
    '!', '|'
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  };
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/* Indexed by syntax code, give the object (cons of syntax code and
   nil) to be stored in syntax table.  Since these objects can be
   shared among syntax tables, we generate them in advance.  By
   sharing objects, the function `describe-syntax' can give a more
   compact listing.  */
static Lisp_Object Vsyntax_code_object;

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/* Look up the value for CHARACTER in syntax table TABLE's parent
   and its parents.  SYNTAX_ENTRY calls this, when TABLE itself has nil
   for CHARACTER.  It's actually used only when not compiled with GCC.  */

Lisp_Object
syntax_parent_lookup (table, character)
     Lisp_Object table;
     int character;
{
  Lisp_Object value;

  while (1)
    {
      table = XCHAR_TABLE (table)->parent;
      if (NILP (table))
	return Qnil;

      value = XCHAR_TABLE (table)->contents[character];
      if (!NILP (value))
	return value;
    }
}

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DEFUN ("char-syntax", Fchar_syntax, Schar_syntax, 1, 1, 0,
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  "Return the syntax code of CHARACTER, described by a character.\n\
For example, if CHARACTER is a word constituent,\n\
the character `w' is returned.\n\
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The characters that correspond to various syntax codes\n\
are listed in the documentation of `modify-syntax-entry'.")
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  (character)
     Lisp_Object character;
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{
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  int char_int;
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  gl_state.current_syntax_table = current_buffer->syntax_table;

  gl_state.use_global = 0;
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  CHECK_NUMBER (character, 0);
  char_int = XINT (character);
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  return make_number (syntax_code_spec[(int) SYNTAX (char_int)]);
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}

DEFUN ("matching-paren", Fmatching_paren, Smatching_paren, 1, 1, 0,
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  "Return the matching parenthesis of CHARACTER, or nil if none.")
  (character)
     Lisp_Object character;
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{
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  int char_int, code;
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  gl_state.current_syntax_table = current_buffer->syntax_table;
  gl_state.use_global = 0;
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  CHECK_NUMBER (character, 0);
  char_int = XINT (character);
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  code = SYNTAX (char_int);
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  if (code == Sopen || code == Sclose)
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    return SYNTAX_MATCH (char_int);
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  return Qnil;
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}

/* This comment supplies the doc string for modify-syntax-entry,
   for make-docfile to see.  We cannot put this in the real DEFUN
   due to limits in the Unix cpp.

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DEFUN ("modify-syntax-entry", foo, bar, 2, 3, 0,
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  "Set syntax for character CHAR according to string S.\n\
The syntax is changed only for table TABLE, which defaults to\n\
 the current buffer's syntax table.\n\
The first character of S should be one of the following:\n\
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  Space or -  whitespace syntax.    w   word constituent.\n\
  _           symbol constituent.   .   punctuation.\n\
  (           open-parenthesis.     )   close-parenthesis.\n\
  \"           string quote.         \\   escape.\n\
  $           paired delimiter.     '   expression quote or prefix operator.\n\
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  <           comment starter.      >   comment ender.\n\
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  /           character-quote.      @   inherit from `standard-syntax-table'.\n\
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\n\
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Only single-character comment start and end sequences are represented thus.\n\
Two-character sequences are represented as described below.\n\
The second character of S is the matching parenthesis,\n\
 used only if the first character is `(' or `)'.\n\
Any additional characters are flags.\n\
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Defined flags are the characters 1, 2, 3, 4, b, and p.\n\
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 1 means CHAR is the start of a two-char comment start sequence.\n\
 2 means CHAR is the second character of such a sequence.\n\
 3 means CHAR is the start of a two-char comment end sequence.\n\
 4 means CHAR is the second character of such a sequence.\n\
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\n\
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There can be up to two orthogonal comment sequences.  This is to support\n\
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language modes such as C++.  By default, all comment sequences are of style\n\
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a, but you can set the comment sequence style to b (on the second character\n\
of a comment-start, or the first character of a comment-end sequence) using\n\
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this flag:\n\
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 b means CHAR is part of comment sequence b.\n\
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\n\
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 p means CHAR is a prefix character for `backward-prefix-chars';\n\
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   such characters are treated as whitespace when they occur\n\
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   between expressions.")
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  (char, s, table)
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*/

DEFUN ("modify-syntax-entry", Fmodify_syntax_entry, Smodify_syntax_entry, 2, 3, 
  /* I really don't know why this is interactive
     help-form should at least be made useful whilst reading the second arg
   */
  "cSet syntax for character: \nsSet syntax for %s to: ",
  0 /* See immediately above */)
  (c, newentry, syntax_table)
     Lisp_Object c, newentry, syntax_table;
{
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  register unsigned char *p;
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  register enum syntaxcode code;
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  int val;
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  Lisp_Object match;
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  CHECK_NUMBER (c, 0);
  CHECK_STRING (newentry, 1);
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  if (NILP (syntax_table))
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    syntax_table = current_buffer->syntax_table;
  else
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    check_syntax_table (syntax_table);
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  p = XSTRING (newentry)->data;
  code = (enum syntaxcode) syntax_spec_code[*p++];
  if (((int) code & 0377) == 0377)
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    error ("invalid syntax description letter: %c", p[-1]);
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  if (code == Sinherit)
    {
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      SET_RAW_SYNTAX_ENTRY (syntax_table, XINT (c), Qnil);
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      return Qnil;
    }

  if (*p)
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    {
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      int len;
      int character = STRING_CHAR_AND_LENGTH (p, XSTRING (newentry)->size - 1,
					      len);
      XSETINT (match, character);
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      if (XFASTINT (match) == ' ')
	match = Qnil;
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      p += len;
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    }
  else
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    match = Qnil;
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  val = (int) code;
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  while (*p)
    switch (*p++)
      {
      case '1':
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	val |= 1 << 16;
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	break;

      case '2':
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	val |= 1 << 17;
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	break;

      case '3':
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	val |= 1 << 18;
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	break;

      case '4':
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	val |= 1 << 19;
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	break;

      case 'p':
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	val |= 1 << 20;
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	break;
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      case 'b':
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	val |= 1 << 21;
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	break;
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      }
	
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  if (val < XVECTOR (Vsyntax_code_object)->size && NILP (match))
    newentry = XVECTOR (Vsyntax_code_object)->contents[val];
  else
    /* Since we can't use a shared object, let's make a new one.  */
    newentry = Fcons (make_number (val), match);
    
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  SET_RAW_SYNTAX_ENTRY (syntax_table, XINT (c), newentry);
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  return Qnil;
}

/* Dump syntax table to buffer in human-readable format */

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static void
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describe_syntax (value)
    Lisp_Object value;
{
  register enum syntaxcode code;
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  char desc, match, start1, start2, end1, end2, prefix, comstyle;
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  char str[2];
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  Lisp_Object first, match_lisp;
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  Findent_to (make_number (16), make_number (1));

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  if (NILP (value))
    {
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      insert_string ("default\n");
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      return;
    }

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  if (CHAR_TABLE_P (value))
    {
      insert_string ("deeper char-table ...\n");
      return;
    }

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  if (!CONSP (value))
    {
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      insert_string ("invalid\n");
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      return;
    }

  first = XCONS (value)->car;
  match_lisp = XCONS (value)->cdr;

  if (!INTEGERP (first) || !(NILP (match_lisp) || INTEGERP (match_lisp)))
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    {
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      insert_string ("invalid\n");
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      return;
    }

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  code = (enum syntaxcode) (XINT (first) & 0377);
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  start1 = (XINT (first) >> 16) & 1;
  start2 = (XINT (first) >> 17) & 1;
  end1 = (XINT (first) >> 18) & 1;
  end2 = (XINT (first) >> 19) & 1;
  prefix = (XINT (first) >> 20) & 1;
  comstyle = (XINT (first) >> 21) & 1;
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  if ((int) code < 0 || (int) code >= (int) Smax)
    {
      insert_string ("invalid");
      return;
    }
  desc = syntax_code_spec[(int) code];

  str[0] = desc, str[1] = 0;
  insert (str, 1);

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  if (NILP (match_lisp))
    insert (" ", 1);
  else
    insert_char (XINT (match_lisp));
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  if (start1)
    insert ("1", 1);
  if (start2)
    insert ("2", 1);

  if (end1)
    insert ("3", 1);
  if (end2)
    insert ("4", 1);

  if (prefix)
    insert ("p", 1);
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  if (comstyle)
    insert ("b", 1);
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  insert_string ("\twhich means: ");

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  switch (SWITCH_ENUM_CAST (code))
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    {
    case Swhitespace:
      insert_string ("whitespace"); break;
    case Spunct:
      insert_string ("punctuation"); break;
    case Sword:
      insert_string ("word"); break;
    case Ssymbol:
      insert_string ("symbol"); break;
    case Sopen:
      insert_string ("open"); break;
    case Sclose:
      insert_string ("close"); break;
    case Squote:
      insert_string ("quote"); break;
    case Sstring:
      insert_string ("string"); break;
    case Smath:
      insert_string ("math"); break;
    case Sescape:
      insert_string ("escape"); break;
    case Scharquote:
      insert_string ("charquote"); break;
    case Scomment:
      insert_string ("comment"); break;
    case Sendcomment:
      insert_string ("endcomment"); break;
    default:
      insert_string ("invalid");
      return;
    }

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  if (!NILP (match_lisp))
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    {
      insert_string (", matches ");
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      insert_char (XINT (match_lisp));
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    }

  if (start1)
    insert_string (",\n\t  is the first character of a comment-start sequence");
  if (start2)
    insert_string (",\n\t  is the second character of a comment-start sequence");

  if (end1)
    insert_string (",\n\t  is the first character of a comment-end sequence");
  if (end2)
    insert_string (",\n\t  is the second character of a comment-end sequence");
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  if (comstyle)
    insert_string (" (comment style b)");

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  if (prefix)
    insert_string (",\n\t  is a prefix character for `backward-prefix-chars'");

  insert_string ("\n");
}

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static Lisp_Object
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describe_syntax_1 (vector)
     Lisp_Object vector;
{
  struct buffer *old = current_buffer;
  set_buffer_internal (XBUFFER (Vstandard_output));
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  describe_vector (vector, Qnil, describe_syntax, 0, Qnil, Qnil, (int *) 0, 0);
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  while (! NILP (XCHAR_TABLE (vector)->parent))
    {
      vector = XCHAR_TABLE (vector)->parent;
      insert_string ("\nThe parent syntax table is:");
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      describe_vector (vector, Qnil, describe_syntax, 0, Qnil, Qnil,
		       (int *) 0, 0);
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    }
	
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  call0 (intern ("help-mode"));
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  set_buffer_internal (old);
  return Qnil;
}

DEFUN ("describe-syntax", Fdescribe_syntax, Sdescribe_syntax, 0, 0, "",
  "Describe the syntax specifications in the syntax table.\n\
The descriptions are inserted in a buffer, which is then displayed.")
  ()
{
  internal_with_output_to_temp_buffer
     ("*Help*", describe_syntax_1, current_buffer->syntax_table);

  return Qnil;
}

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int parse_sexp_ignore_comments;

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/* Return the position across COUNT words from FROM.
   If that many words cannot be found before the end of the buffer, return 0.
   COUNT negative means scan backward and stop at word beginning.  */

scan_words (from, count)
     register int from, count;
{
  register int beg = BEGV;
  register int end = ZV;
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  register enum syntaxcode code;
  int ch0, ch1;
  int temp_pos;
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  immediate_quit = 1;
  QUIT;

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  SETUP_SYNTAX_TABLE (from, count);

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  while (count > 0)
    {
      while (1)
	{
	  if (from == end)
	    {
	      immediate_quit = 0;
	      return 0;
	    }
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	  UPDATE_SYNTAX_TABLE_FORWARD (from);
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	  ch0 = FETCH_CHAR (from);
	  code = SYNTAX (ch0);
	  INC_POS (from);
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	  if (words_include_escapes
	      && (code == Sescape || code == Scharquote))
	    break;
	  if (code == Sword)
	    break;
	}
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      /* Now CH0 is a character which begins a word and FROM is the
         position of the next character.  */
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      while (1)
	{
	  if (from == end) break;
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	  UPDATE_SYNTAX_TABLE_FORWARD (from);
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	  ch1 = FETCH_CHAR (from);
	  code = SYNTAX (ch1);
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	  if (!(words_include_escapes
		&& (code == Sescape || code == Scharquote)))
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	    if (code != Sword || WORD_BOUNDARY_P (ch0, ch1))
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	      break;
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	  INC_POS (from);
	  ch0 = ch1;
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	}
      count--;
    }
  while (count < 0)
    {
      while (1)
	{
	  if (from == beg)
	    {
	      immediate_quit = 0;
	      return 0;
	    }
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	  DEC_POS (from);
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	  UPDATE_SYNTAX_TABLE_BACKWARD (from);
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	  ch1 = FETCH_CHAR (from);
	  code = SYNTAX (ch1);
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	  if (words_include_escapes
	      && (code == Sescape || code == Scharquote))
	    break;
	  if (code == Sword)
	    break;
	}
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      /* Now CH1 is a character which ends a word and FROM is the
         position of it.  */
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      while (1)
	{
	  if (from == beg) break;
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	  temp_pos = from;
	  DEC_POS (temp_pos);
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	  UPDATE_SYNTAX_TABLE_BACKWARD (from);
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	  ch0 = FETCH_CHAR (temp_pos);
	  code = SYNTAX (ch0);
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	  if (!(words_include_escapes
		&& (code == Sescape || code == Scharquote)))
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	    if (code != Sword || WORD_BOUNDARY_P (ch0, ch1))
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	      break;
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	  from = temp_pos;
	  ch1 = ch0;
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	}
      count++;
    }

  immediate_quit = 0;

  return from;
}

DEFUN ("forward-word", Fforward_word, Sforward_word, 1, 1, "p",
  "Move point forward ARG words (backward if ARG is negative).\n\
Normally returns t.\n\
If an edge of the buffer is reached, point is left there\n\
and nil is returned.")
  (count)
     Lisp_Object count;
{
  int val;
  CHECK_NUMBER (count, 0);

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  if (!(val = scan_words (PT, XINT (count))))
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    {
      SET_PT (XINT (count) > 0 ? ZV : BEGV);
      return Qnil;
    }
  SET_PT (val);
  return Qt;
}

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Lisp_Object skip_chars ();

DEFUN ("skip-chars-forward", Fskip_chars_forward, Sskip_chars_forward, 1, 2, 0,
  "Move point forward, stopping before a char not in STRING, or at pos LIM.\n\
STRING is like the inside of a `[...]' in a regular expression\n\
except that `]' is never special and `\\' quotes `^', `-' or `\\'.\n\
Thus, with arg \"a-zA-Z\", this skips letters stopping before first nonletter.\n\
With arg \"^a-zA-Z\", skips nonletters stopping before first letter.\n\
Returns the distance traveled, either zero or positive.")
  (string, lim)
     Lisp_Object string, lim;
{
  return skip_chars (1, 0, string, lim);
}

DEFUN ("skip-chars-backward", Fskip_chars_backward, Sskip_chars_backward, 1, 2, 0,
  "Move point backward, stopping after a char not in STRING, or at pos LIM.\n\
See `skip-chars-forward' for details.\n\
Returns the distance traveled, either zero or negative.")
  (string, lim)
     Lisp_Object string, lim;
{
  return skip_chars (0, 0, string, lim);
}

DEFUN ("skip-syntax-forward", Fskip_syntax_forward, Sskip_syntax_forward, 1, 2, 0,
  "Move point forward across chars in specified syntax classes.\n\
SYNTAX is a string of syntax code characters.\n\
Stop before a char whose syntax is not in SYNTAX, or at position LIM.\n\
If SYNTAX starts with ^, skip characters whose syntax is NOT in SYNTAX.\n\
This function returns the distance traveled, either zero or positive.")
  (syntax, lim)
     Lisp_Object syntax, lim;
{
  return skip_chars (1, 1, syntax, lim);
}

DEFUN ("skip-syntax-backward", Fskip_syntax_backward, Sskip_syntax_backward, 1, 2, 0,
  "Move point backward across chars in specified syntax classes.\n\
SYNTAX is a string of syntax code characters.\n\
Stop on reaching a char whose syntax is not in SYNTAX, or at position LIM.\n\
If SYNTAX starts with ^, skip characters whose syntax is NOT in SYNTAX.\n\
This function returns the distance traveled, either zero or negative.")
  (syntax, lim)
     Lisp_Object syntax, lim;
{
  return skip_chars (0, 1, syntax, lim);
}

Lisp_Object
skip_chars (forwardp, syntaxp, string, lim)
     int forwardp, syntaxp;
     Lisp_Object string, lim;
{
  register unsigned char *p, *pend;
  register unsigned int c;
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  register int ch;
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  unsigned char fastmap[0400];
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  /* If SYNTAXP is 0, STRING may contain multi-byte form of characters
     of which codes don't fit in FASTMAP.  In that case, we set the
     first byte of multibyte form (i.e. base leading-code) in FASTMAP
     and set the actual ranges of characters in CHAR_RANGES.  In the
     form "X-Y" of STRING, both X and Y must belong to the same
     character set because a range striding across character sets is
     meaningless.  */
1147
  int *char_ranges;
1148
  int n_char_ranges = 0;
1149 1150
  int negate = 0;
  register int i;
1151
  int multibyte = !NILP (current_buffer->enable_multibyte_characters);
1152 1153

  CHECK_STRING (string, 0);
1154
  char_ranges = (int *) alloca (XSTRING (string)->size * (sizeof (int)) * 2);
1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184

  if (NILP (lim))
    XSETINT (lim, forwardp ? ZV : BEGV);
  else
    CHECK_NUMBER_COERCE_MARKER (lim, 1);

  /* In any case, don't allow scan outside bounds of buffer.  */
  /* jla turned this off, for no known reason.
     bfox turned the ZV part on, and rms turned the
     BEGV part back on.  */
  if (XINT (lim) > ZV)
    XSETFASTINT (lim, ZV);
  if (XINT (lim) < BEGV)
    XSETFASTINT (lim, BEGV);

  p = XSTRING (string)->data;
  pend = p + XSTRING (string)->size;
  bzero (fastmap, sizeof fastmap);

  if (p != pend && *p == '^')
    {
      negate = 1; p++;
    }

  /* Find the characters specified and set their elements of fastmap.
     If syntaxp, each character counts as itself.
     Otherwise, handle backslashes and ranges specially.  */

  while (p != pend)
    {
1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195
      c = *p;
      if (multibyte)
	{
	  ch = STRING_CHAR (p, pend - p);
	  p += BYTES_BY_CHAR_HEAD (*p);
	}
      else
	{
	  ch = c;
	  p++;
	}
1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206
      if (syntaxp)
	fastmap[syntax_spec_code[c]] = 1;
      else
	{
	  if (c == '\\')
	    {
	      if (p == pend) break;
	      c = *p++;
	    }
	  if (p != pend && *p == '-')
	    {
1207 1208
	      unsigned int ch2;

1209 1210
	      p++;
	      if (p == pend) break;
1211 1212 1213 1214 1215 1216 1217
	      if (SINGLE_BYTE_CHAR_P (ch))
		while (c <= *p)
		  {
		    fastmap[c] = 1;
		    c++;
		  }
	      else
1218
		{
1219 1220 1221 1222 1223
		  fastmap[c] = 1; /* C is the base leading-code.  */
		  ch2 = STRING_CHAR (p, pend - p);
		  if (ch <= ch2)
		    char_ranges[n_char_ranges++] = ch,
		    char_ranges[n_char_ranges++] = ch2;
1224
		}
1225
	      p += multibyte ? BYTES_BY_CHAR_HEAD (*p) : 1;
1226 1227
	    }
	  else
1228 1229 1230 1231 1232 1233 1234 1235
	    {
	      fastmap[c] = 1;
	      if (!SINGLE_BYTE_CHAR_P (ch))
		{
		  char_ranges[n_char_ranges++] = ch;
		  char_ranges[n_char_ranges++] = ch;
		}
	    }
1236 1237 1238
	}
    }

1239 1240 1241 1242
  /* If ^ was the first character, complement the fastmap.  In
     addition, as all multibyte characters have possibility of
     matching, set all entries for base leading codes, which is
     harmless even if SYNTAXP is 1.  */
1243 1244 1245

  if (negate)
    for (i = 0; i < sizeof fastmap; i++)
1246 1247 1248 1249 1250 1251
      {
	if (!multibyte || !BASE_LEADING_CODE_P (i))
	  fastmap[i] ^= 1;
	else
	  fastmap[i] = 1;
      }
1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262

  {
    int start_point = PT;
    int pos = PT;

    immediate_quit = 1;
    if (syntaxp)
      {
        SETUP_SYNTAX_TABLE (pos, forwardp ? 1 : -1);
	if (forwardp)
	  {
1263
	    if (multibyte)
1264
	      {
1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279
		while (pos < XINT (lim)
		       && fastmap[(int) SYNTAX (FETCH_CHAR (pos))])
		  {
		    INC_POS (pos);
		    UPDATE_SYNTAX_TABLE_FORWARD (pos);
		  }
	      }
	    else
	      {
		while (pos < XINT (lim)
		       && fastmap[(int) SYNTAX (FETCH_BYTE (pos))])
		  {
		    pos++;
		    UPDATE_SYNTAX_TABLE_FORWARD (pos);
		  }
1280 1281 1282 1283
	      }
	  }
	else
	  {
1284
	    if (multibyte)
1285
	      {
1286 1287 1288 1289
		while (pos > XINT (lim))
		  {
		    int savepos = pos;
		    DEC_POS (pos);
1290
		    UPDATE_SYNTAX_TABLE_BACKWARD (pos);
1291 1292 1293 1294 1295 1296 1297 1298 1299
		    if (!fastmap[(int) SYNTAX (FETCH_CHAR (pos))])
		      {
			pos = savepos;
			break;
		      }
		  }
	      }
	    else
	      {
1300
		while (pos > XINT (lim))
1301 1302
		  {
		    pos--;
1303 1304 1305 1306 1307 1308
		    UPDATE_SYNTAX_TABLE_BACKWARD (pos);
		    if (!fastmap[(int) SYNTAX (FETCH_BYTE (pos))])
		      {
			pos++;
			break;
		      }
1309
		  }
1310 1311 1312 1313 1314 1315 1316
	      }
	  }
      }
    else
      {
	if (forwardp)
	  {
1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343
	    if (multibyte)
	      while (pos < XINT (lim) && fastmap[(c = FETCH_BYTE (pos))])
		{
		  if (!BASE_LEADING_CODE_P (c))
		    pos++;
		  else if (n_char_ranges)
		    {
		      /* We much check CHAR_RANGES for a multibyte
			 character.  */
		      ch = FETCH_MULTIBYTE_CHAR (pos);
		      for (i = 0; i < n_char_ranges; i += 2)
			if ((ch >= char_ranges[i] && ch <= char_ranges[i + 1]))
			  break;
		      if (!(negate ^ (i < n_char_ranges)))
			break;

		      INC_POS (pos);
		    }
		  else
		    {
		      if (!negate) break;
		      INC_POS (pos);
		    }
		}
	    else
	      while (pos < XINT (lim) && fastmap[FETCH_BYTE (pos)])
		pos++;
1344 1345 1346
	  }
	else
	  {
1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385
	    if (multibyte)
	      while (pos > XINT (lim))
		{
		  int savepos = pos;
		  DEC_POS (pos);
		  if (fastmap[(c = FETCH_BYTE (pos))])
		    {
		      if (!BASE_LEADING_CODE_P (c))
			;
		      else if (n_char_ranges)
			{
			  /* We much check CHAR_RANGES for a multibyte
			     character.  */
			  ch = FETCH_MULTIBYTE_CHAR (pos);
			  for (i = 0; i < n_char_ranges; i += 2)
			    if (ch >= char_ranges[i] && ch <= char_ranges[i + 1])
			      break;
			  if (!(negate ^ (i < n_char_ranges)))
			    {
			      pos = savepos;
			      break;
			    }
			}
		      else
			if (!negate)
			  {
			    pos = savepos;
			    break;
			  }
		    }
		  else
		    {
		      pos = savepos;
		      break;
		    }
		}
	    else
	      while (pos > XINT (lim) && fastmap[FETCH_BYTE (pos - 1)])
		pos--;
1386 1387
	  }
      }
1388 1389 1390 1391 1392 1393

    if (multibyte
	/* INC_POS or DEC_POS might have moved POS over LIM.  */
	&& (forwardp ? (pos > XINT (lim)) : (pos < XINT (lim))))
      pos = XINT (lim);

1394 1395 1396 1397 1398 1399 1400
    SET_PT (pos);
    immediate_quit = 0;

    return make_number (PT - start_point);
  }
}

1401 1402 1403
DEFUN ("forward-comment", Fforward_comment, Sforward_comment, 1, 1, 0,
  "Move forward across up to N comments.  If N is negative, move backward.\n\
Stop scanning if we find something other than a comment or whitespace.\n\
1404
Set point to where scanning stops.\n\
1405 1406 1407
If N comments are found as expected, with nothing except whitespace\n\
between them, return t; otherwise return nil.")
  (count)
1408