fns.c

/* Random utility Lisp functions.
   Copyright (C) 1985, 86, 87, 93, 94, 95, 97, 1998 Free Software Foundation, Inc.

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
the Free Software Foundation; either version 2, or (at your option)
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
the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */


#include <config.h>

/* Note on some machines this defines `vector' as a typedef,
   so make sure we don't use that name in this file.  */
#undef vector
#define vector *****

#include "lisp.h"
#include "commands.h"
#include "charset.h"

#include "buffer.h"
#include "keyboard.h"
#include "intervals.h"
#include "frame.h"
#include "window.h"

#ifndef NULL
#define NULL (void *)0
#endif

/* Nonzero enables use of dialog boxes for questions
   asked by mouse commands.  */
int use_dialog_box;

extern Lisp_Object Flookup_key ();

extern int minibuffer_auto_raise;
extern Lisp_Object minibuf_window;

Lisp_Object Qstring_lessp, Qprovide, Qrequire;
Lisp_Object Qyes_or_no_p_history;
Lisp_Object Qcursor_in_echo_area;
Lisp_Object Qwidget_type;

static int internal_equal ();

DEFUN ("identity", Fidentity, Sidentity, 1, 1, 0,
  "Return the argument unchanged.")
  (arg)
     Lisp_Object arg;
{
  return arg;
}

extern long get_random ();
extern void seed_random ();
extern long time ();

DEFUN ("random", Frandom, Srandom, 0, 1, 0,
  "Return a pseudo-random number.\n\
All integers representable in Lisp are equally likely.\n\
  On most systems, this is 28 bits' worth.\n\
With positive integer argument N, return random number in interval [0,N).\n\
With argument t, set the random number seed from the current time and pid.")
  (n)
     Lisp_Object n;
{
  EMACS_INT val;
  Lisp_Object lispy_val;
  unsigned long denominator;

  if (EQ (n, Qt))
    seed_random (getpid () + time (NULL));
  if (NATNUMP (n) && XFASTINT (n) != 0)
    {
      /* Try to take our random number from the higher bits of VAL,
	 not the lower, since (says Gentzel) the low bits of `random'
	 are less random than the higher ones.  We do this by using the
	 quotient rather than the remainder.  At the high end of the RNG
	 it's possible to get a quotient larger than n; discarding
	 these values eliminates the bias that would otherwise appear
	 when using a large n.  */
      denominator = ((unsigned long)1 << VALBITS) / XFASTINT (n);
      do
	val = get_random () / denominator;
      while (val >= XFASTINT (n));
    }
  else
    val = get_random ();
  XSETINT (lispy_val, val);
  return lispy_val;
}

/* Random data-structure functions */

DEFUN ("length", Flength, Slength, 1, 1, 0,
  "Return the length of vector, list or string SEQUENCE.\n\
A byte-code function object is also allowed.\n\
If the string contains multibyte characters, this is not the necessarily\n\
the number of characters in the string; it is the number of bytes.\n\
To get the number of characters, use `chars-in-string'")
  (sequence)
     register Lisp_Object sequence;
{
  register Lisp_Object tail, val;
  register int i;

 retry:
  if (STRINGP (sequence))
    XSETFASTINT (val, XSTRING (sequence)->size);
  else if (VECTORP (sequence))
    XSETFASTINT (val, XVECTOR (sequence)->size);
  else if (CHAR_TABLE_P (sequence))
    XSETFASTINT (val, (MIN_CHAR_COMPOSITION
		       + (CHAR_FIELD2_MASK | CHAR_FIELD3_MASK)
		       - 1));
  else if (BOOL_VECTOR_P (sequence))
    XSETFASTINT (val, XBOOL_VECTOR (sequence)->size);
  else if (COMPILEDP (sequence))
    XSETFASTINT (val, XVECTOR (sequence)->size & PSEUDOVECTOR_SIZE_MASK);
  else if (CONSP (sequence))
    {
      for (i = 0, tail = sequence; !NILP (tail); i++)
	{
	  QUIT;
	  tail = Fcdr (tail);
	}

      XSETFASTINT (val, i);
    }
  else if (NILP (sequence))
    XSETFASTINT (val, 0);
  else
    {
      sequence = wrong_type_argument (Qsequencep, sequence);
      goto retry;
    }
  return val;
}

/* This does not check for quits.  That is safe
   since it must terminate.  */

DEFUN ("safe-length", Fsafe_length, Ssafe_length, 1, 1, 0,
  "Return the length of a list, but avoid error or infinite loop.\n\
This function never gets an error.  If LIST is not really a list,\n\
it returns 0.  If LIST is circular, it returns a finite value\n\
which is at least the number of distinct elements.")
  (list)
     Lisp_Object list;
{
  Lisp_Object tail, halftail, length;
  int len = 0;

  /* halftail is used to detect circular lists.  */
  halftail = list;
  for (tail = list; CONSP (tail); tail = XCONS (tail)->cdr)
    {
      if (EQ (tail, halftail) && len != 0)
	break;
      len++;
      if ((len & 1) == 0)
	halftail = XCONS (halftail)->cdr;
    }

  XSETINT (length, len);
  return length;
}

DEFUN ("string-bytes", Fstring_bytes, Sstring_bytes, 1, 1, 0,
  "Return the number of bytes in STRING.\n\
If STRING is a multibyte string, this is greater than the length of STRING.")
  (string)
     Lisp_Object string;
{
  CHECK_STRING (string, 1);
  return make_number (STRING_BYTES (XSTRING (string)));
}

DEFUN ("string-equal", Fstring_equal, Sstring_equal, 2, 2, 0,
  "Return t if two strings have identical contents.\n\
Case is significant, but text properties are ignored.\n\
Symbols are also allowed; their print names are used instead.")
  (s1, s2)
     register Lisp_Object s1, s2;
{
  if (SYMBOLP (s1))
    XSETSTRING (s1, XSYMBOL (s1)->name);
  if (SYMBOLP (s2))
    XSETSTRING (s2, XSYMBOL (s2)->name);
  CHECK_STRING (s1, 0);
  CHECK_STRING (s2, 1);

  if (XSTRING (s1)->size != XSTRING (s2)->size
      || STRING_BYTES (XSTRING (s1)) != STRING_BYTES (XSTRING (s2))
      || bcmp (XSTRING (s1)->data, XSTRING (s2)->data, STRING_BYTES (XSTRING (s1))))
    return Qnil;
  return Qt;
}

DEFUN ("string-lessp", Fstring_lessp, Sstring_lessp, 2, 2, 0,
  "Return t if first arg string is less than second in lexicographic order.\n\
Case is significant.\n\
Symbols are also allowed; their print names are used instead.")
  (s1, s2)
     register Lisp_Object s1, s2;
{
  register int end;
  register int i1, i1_byte, i2, i2_byte;

  if (SYMBOLP (s1))
    XSETSTRING (s1, XSYMBOL (s1)->name);
  if (SYMBOLP (s2))
    XSETSTRING (s2, XSYMBOL (s2)->name);
  CHECK_STRING (s1, 0);
  CHECK_STRING (s2, 1);

  i1 = i1_byte = i2 = i2_byte = 0;

  end = XSTRING (s1)->size;
  if (end > XSTRING (s2)->size)
    end = XSTRING (s2)->size;

  while (i1 < end)
    {
      /* When we find a mismatch, we must compare the
	 characters, not just the bytes.  */
      int c1, c2;

      if (STRING_MULTIBYTE (s1))
	FETCH_STRING_CHAR_ADVANCE (c1, s1, i1, i1_byte);
      else
	c1 = XSTRING (s1)->data[i1++];

      if (STRING_MULTIBYTE (s2))
	FETCH_STRING_CHAR_ADVANCE (c2, s2, i2, i2_byte);
      else
	c2 = XSTRING (s2)->data[i2++];

      if (c1 != c2)
	return c1 < c2 ? Qt : Qnil;
    }
  return i1 < XSTRING (s2)->size ? Qt : Qnil;
}

static Lisp_Object concat ();

/* ARGSUSED */
Lisp_Object
concat2 (s1, s2)
     Lisp_Object s1, s2;
{
#ifdef NO_ARG_ARRAY
  Lisp_Object args[2];
  args[0] = s1;
  args[1] = s2;
  return concat (2, args, Lisp_String, 0);
#else
  return concat (2, &s1, Lisp_String, 0);
#endif /* NO_ARG_ARRAY */
}

/* ARGSUSED */
Lisp_Object
concat3 (s1, s2, s3)
     Lisp_Object s1, s2, s3;
{
#ifdef NO_ARG_ARRAY
  Lisp_Object args[3];
  args[0] = s1;
  args[1] = s2;
  args[2] = s3;
  return concat (3, args, Lisp_String, 0);
#else
  return concat (3, &s1, Lisp_String, 0);
#endif /* NO_ARG_ARRAY */
}

DEFUN ("append", Fappend, Sappend, 0, MANY, 0,
  "Concatenate all the arguments and make the result a list.\n\
The result is a list whose elements are the elements of all the arguments.\n\
Each argument may be a list, vector or string.\n\
The last argument is not copied, just used as the tail of the new list.")
  (nargs, args)
     int nargs;
     Lisp_Object *args;
{
  return concat (nargs, args, Lisp_Cons, 1);
}

DEFUN ("concat", Fconcat, Sconcat, 0, MANY, 0,
  "Concatenate all the arguments and make the result a string.\n\
The result is a string whose elements are the elements of all the arguments.\n\
Each argument may be a string or a list or vector of characters (integers).\n\
\n\
Do not use individual integers as arguments!\n\
The behavior of `concat' in that case will be changed later!\n\
If your program passes an integer as an argument to `concat',\n\
you should change it right away not to do so.")
  (nargs, args)
     int nargs;
     Lisp_Object *args;
{
  return concat (nargs, args, Lisp_String, 0);
}

DEFUN ("vconcat", Fvconcat, Svconcat, 0, MANY, 0,
  "Concatenate all the arguments and make the result a vector.\n\
The result is a vector whose elements are the elements of all the arguments.\n\
Each argument may be a list, vector or string.")
  (nargs, args)
     int nargs;
     Lisp_Object *args;
{
  return concat (nargs, args, Lisp_Vectorlike, 0);
}

/* Retrun a copy of a sub char table ARG.  The elements except for a
   nested sub char table are not copied.  */
static Lisp_Object
copy_sub_char_table (arg)
     Lisp_Object arg;
{
  Lisp_Object copy = make_sub_char_table (XCHAR_TABLE (arg)->defalt);
  int i;

  /* Copy all the contents.  */
  bcopy (XCHAR_TABLE (arg)->contents, XCHAR_TABLE (copy)->contents,
	 SUB_CHAR_TABLE_ORDINARY_SLOTS * sizeof (Lisp_Object));
  /* Recursively copy any sub char-tables in the ordinary slots.  */
  for (i = 32; i < SUB_CHAR_TABLE_ORDINARY_SLOTS; i++)
    if (SUB_CHAR_TABLE_P (XCHAR_TABLE (arg)->contents[i]))
      XCHAR_TABLE (copy)->contents[i]
	= copy_sub_char_table (XCHAR_TABLE (copy)->contents[i]);

  return copy;
}


DEFUN ("copy-sequence", Fcopy_sequence, Scopy_sequence, 1, 1, 0,
  "Return a copy of a list, vector or string.\n\
The elements of a list or vector are not copied; they are shared\n\
with the original.")
  (arg)
     Lisp_Object arg;
{
  if (NILP (arg)) return arg;

  if (CHAR_TABLE_P (arg))
    {
      int i;
      Lisp_Object copy;

      copy = Fmake_char_table (XCHAR_TABLE (arg)->purpose, Qnil);
      /* Copy all the slots, including the extra ones.  */
      bcopy (XVECTOR (arg)->contents, XVECTOR (copy)->contents,
	     ((XCHAR_TABLE (arg)->size & PSEUDOVECTOR_SIZE_MASK)
	      * sizeof (Lisp_Object)));

      /* Recursively copy any sub char tables in the ordinary slots
         for multibyte characters.  */
      for (i = CHAR_TABLE_SINGLE_BYTE_SLOTS;
	   i < CHAR_TABLE_ORDINARY_SLOTS; i++)
	if (SUB_CHAR_TABLE_P (XCHAR_TABLE (arg)->contents[i]))
	  XCHAR_TABLE (copy)->contents[i]
	    = copy_sub_char_table (XCHAR_TABLE (copy)->contents[i]);

      return copy;
    }

  if (BOOL_VECTOR_P (arg))
    {
      Lisp_Object val;
      int size_in_chars
	= (XBOOL_VECTOR (arg)->size + BITS_PER_CHAR - 1) / BITS_PER_CHAR;

      val = Fmake_bool_vector (Flength (arg), Qnil);
      bcopy (XBOOL_VECTOR (arg)->data, XBOOL_VECTOR (val)->data,
	     size_in_chars);
      return val;
    }

  if (!CONSP (arg) && !VECTORP (arg) && !STRINGP (arg))
    arg = wrong_type_argument (Qsequencep, arg);
  return concat (1, &arg, CONSP (arg) ? Lisp_Cons : XTYPE (arg), 0);
}

static Lisp_Object
concat (nargs, args, target_type, last_special)
     int nargs;
     Lisp_Object *args;
     enum Lisp_Type target_type;
     int last_special;
{
  Lisp_Object val;
  register Lisp_Object tail;
  register Lisp_Object this;
  int toindex;
  int toindex_byte;
  register int result_len;
  register int result_len_byte;
  register int argnum;
  Lisp_Object last_tail;
  Lisp_Object prev;
  int some_multibyte;

  /* In append, the last arg isn't treated like the others */
  if (last_special && nargs > 0)
    {
      nargs--;
      last_tail = args[nargs];
    }
  else
    last_tail = Qnil;

  /* Canonicalize each argument.  */
  for (argnum = 0; argnum < nargs; argnum++)
    {
      this = args[argnum];
      if (!(CONSP (this) || NILP (this) || VECTORP (this) || STRINGP (this)
	    || COMPILEDP (this) || BOOL_VECTOR_P (this)))
	{
	  if (INTEGERP (this))
            args[argnum] = Fnumber_to_string (this);
	  else
	    args[argnum] = wrong_type_argument (Qsequencep, this);
	}
    }

  /* Compute total length in chars of arguments in RESULT_LEN.
     If desired output is a string, also compute length in bytes
     in RESULT_LEN_BYTE, and determine in SOME_MULTIBYTE
     whether the result should be a multibyte string.  */
  result_len_byte = 0;
  result_len = 0;
  some_multibyte = 0;
  for (argnum = 0; argnum < nargs; argnum++)
    {
      int len;
      this = args[argnum];
      len = XFASTINT (Flength (this));
      if (target_type == Lisp_String)
	{
	  /* We must count the number of bytes needed in the string
	     as well as the number of characters.  */
	  int i;
	  Lisp_Object ch;
	  int this_len_byte;

	  if (VECTORP (this))
	    for (i = 0; i < len; i++)
	      {
		ch = XVECTOR (this)->contents[i];
		if (! INTEGERP (ch))
		  wrong_type_argument (Qintegerp, ch);
		this_len_byte = XFASTINT (Fchar_bytes (ch));
		result_len_byte += this_len_byte;
		if (this_len_byte > 1)
		  some_multibyte = 1;
	      }
	  else if (BOOL_VECTOR_P (this) && XBOOL_VECTOR (this)->size > 0)
	    wrong_type_argument (Qintegerp, Faref (this, make_number (0)));
	  else if (CONSP (this))
	    for (; CONSP (this); this = XCONS (this)->cdr)
	      {
		ch = XCONS (this)->car;
		if (! INTEGERP (ch))
		  wrong_type_argument (Qintegerp, ch);
		this_len_byte = XFASTINT (Fchar_bytes (ch));
		result_len_byte += this_len_byte;
		if (this_len_byte > 1)
		  some_multibyte = 1;
	      }
	  else if (STRINGP (this))
	    {
	      if (STRING_MULTIBYTE (this))
		{
		  some_multibyte = 1;
		  result_len_byte += STRING_BYTES (XSTRING (this));
		}
	      else
		result_len_byte += count_size_as_multibyte (XSTRING (this)->data,
							    XSTRING (this)->size);
	    }
	}

      result_len += len;
    }

  if (! some_multibyte)
    result_len_byte = result_len;

  /* Create the output object.  */
  if (target_type == Lisp_Cons)
    val = Fmake_list (make_number (result_len), Qnil);
  else if (target_type == Lisp_Vectorlike)
    val = Fmake_vector (make_number (result_len), Qnil);
  else
    val = make_uninit_multibyte_string (result_len, result_len_byte);

  /* In `append', if all but last arg are nil, return last arg.  */
  if (target_type == Lisp_Cons && EQ (val, Qnil))
    return last_tail;

  /* Copy the contents of the args into the result.  */
  if (CONSP (val))
    tail = val, toindex = -1;		/* -1 in toindex is flag we are making a list */
  else
    toindex = 0, toindex_byte = 0;

  prev = Qnil;

  for (argnum = 0; argnum < nargs; argnum++)
    {
      Lisp_Object thislen;
      int thisleni;
      register unsigned int thisindex = 0;
      register unsigned int thisindex_byte = 0;

      this = args[argnum];
      if (!CONSP (this))
	thislen = Flength (this), thisleni = XINT (thislen);

      if (STRINGP (this) && STRINGP (val)
	  && ! NULL_INTERVAL_P (XSTRING (this)->intervals))
	copy_text_properties (make_number (0), thislen, this,
			      make_number (toindex), val, Qnil);

      /* Between strings of the same kind, copy fast.  */
      if (STRINGP (this) && STRINGP (val)
	  && STRING_MULTIBYTE (this) == some_multibyte)
	{
	  int thislen_byte = STRING_BYTES (XSTRING (this));
	  bcopy (XSTRING (this)->data, XSTRING (val)->data + toindex_byte,
		 STRING_BYTES (XSTRING (this)));
	  toindex_byte += thislen_byte;
	  toindex += thisleni;
	}
      /* Copy a single-byte string to a multibyte string.  */
      else if (STRINGP (this) && STRINGP (val))
	{
	  toindex_byte += copy_text (XSTRING (this)->data,
				     XSTRING (val)->data + toindex_byte,
				     XSTRING (this)->size, 0, 1);
	  toindex += thisleni;
	}
      else
	/* Copy element by element.  */
	while (1)
	  {
	    register Lisp_Object elt;

	    /* Fetch next element of `this' arg into `elt', or break if
	       `this' is exhausted. */
	    if (NILP (this)) break;
	    if (CONSP (this))
	      elt = XCONS (this)->car, this = XCONS (this)->cdr;
	    else if (thisindex >= thisleni)
	      break;
	    else if (STRINGP (this))
	      {
		int c;
		if (STRING_MULTIBYTE (this))
		  {
		    FETCH_STRING_CHAR_ADVANCE (c, this,
					       thisindex,
					       thisindex_byte);
		    XSETFASTINT (elt, c);
		  }
		else
		  {
		    XSETFASTINT (elt, XSTRING (this)->data[thisindex++]);
		    if (some_multibyte && XINT (elt) >= 0200
			&& XINT (elt) < 0400)
		      {
			c = unibyte_char_to_multibyte (XINT (elt));
			XSETINT (elt, c);
		      }
		  }
	      }
	    else if (BOOL_VECTOR_P (this))
	      {
		int byte;
		byte = XBOOL_VECTOR (this)->data[thisindex / BITS_PER_CHAR];
		if (byte & (1 << (thisindex % BITS_PER_CHAR)))
		  elt = Qt;
		else
		  elt = Qnil;
		thisindex++;
	      }
	    else
	      elt = XVECTOR (this)->contents[thisindex++];

	    /* Store this element into the result.  */
	    if (toindex < 0)
	      {
		XCONS (tail)->car = elt;
		prev = tail;
		tail = XCONS (tail)->cdr;
	      }
	    else if (VECTORP (val))
	      XVECTOR (val)->contents[toindex++] = elt;
	    else
	      {
		CHECK_NUMBER (elt, 0);
		if (SINGLE_BYTE_CHAR_P (XINT (elt)))
		  {
		    XSTRING (val)->data[toindex++] = XINT (elt);
		    toindex_byte++;
		  }
		else
		  /* If we have any multibyte characters,
		     we already decided to make a multibyte string.  */
		  {
		    int c = XINT (elt);
		    unsigned char work[4], *str;
		    int i = CHAR_STRING (c, work, str);

		    /* P exists as a variable
		       to avoid a bug on the Masscomp C compiler.  */
		    unsigned char *p = & XSTRING (val)->data[toindex_byte];
		    bcopy (str, p, i);
		    toindex_byte += i;
		    toindex++;
		  }
	      }
	  }
    }
  if (!NILP (prev))
    XCONS (prev)->cdr = last_tail;

  return val;
}

static Lisp_Object string_char_byte_cache_string;
static int string_char_byte_cache_charpos;
static int string_char_byte_cache_bytepos;

/* Return the character index corresponding to CHAR_INDEX in STRING.  */

int
string_char_to_byte (string, char_index)
     Lisp_Object string;
     int char_index;
{
  int i, i_byte;
  int best_below, best_below_byte;
  int best_above, best_above_byte;

  if (! STRING_MULTIBYTE (string))
    return char_index;

  best_below = best_below_byte = 0;
  best_above = XSTRING (string)->size;
  best_above_byte = STRING_BYTES (XSTRING (string));

  if (EQ (string, string_char_byte_cache_string))
    {
      if (string_char_byte_cache_charpos < char_index)
	{
	  best_below = string_char_byte_cache_charpos;
	  best_below_byte = string_char_byte_cache_bytepos;
	}
      else
	{
	  best_above = string_char_byte_cache_charpos;
	  best_above_byte = string_char_byte_cache_bytepos;
	}
    }

  if (char_index - best_below < best_above - char_index)
    {
      while (best_below < char_index)
	{
	  int c;
	  FETCH_STRING_CHAR_ADVANCE (c, string, best_below, best_below_byte);
	}
      i = best_below;
      i_byte = best_below_byte;
    }
  else
    {
      while (best_above > char_index)
	{
	  int best_above_byte_saved = --best_above_byte;

	  while (best_above_byte > 0
		 && !CHAR_HEAD_P (XSTRING (string)->data[best_above_byte]))
	    best_above_byte--;
	  if (XSTRING (string)->data[best_above_byte] < 0x80)
	    best_above_byte = best_above_byte_saved;
	  best_above--;
	}
      i = best_above;
      i_byte = best_above_byte;
    }

  string_char_byte_cache_bytepos = i_byte;
  string_char_byte_cache_charpos = i;
  string_char_byte_cache_string = string;

  return i_byte;
}

/* Return the character index corresponding to BYTE_INDEX in STRING.  */

int
string_byte_to_char (string, byte_index)
     Lisp_Object string;
     int byte_index;
{
  int i, i_byte;
  int best_below, best_below_byte;
  int best_above, best_above_byte;

  if (! STRING_MULTIBYTE (string))
    return byte_index;

  best_below = best_below_byte = 0;
  best_above = XSTRING (string)->size;
  best_above_byte = STRING_BYTES (XSTRING (string));

  if (EQ (string, string_char_byte_cache_string))
    {
      if (string_char_byte_cache_bytepos < byte_index)
	{
	  best_below = string_char_byte_cache_charpos;
	  best_below_byte = string_char_byte_cache_bytepos;
	}
      else
	{
	  best_above = string_char_byte_cache_charpos;
	  best_above_byte = string_char_byte_cache_bytepos;
	}
    }

  if (byte_index - best_below_byte < best_above_byte - byte_index)
    {
      while (best_below_byte < byte_index)
	{
	  int c;
	  FETCH_STRING_CHAR_ADVANCE (c, string, best_below, best_below_byte);
	}
      i = best_below;
      i_byte = best_below_byte;
    }
  else
    {
      while (best_above_byte > byte_index)
	{
	  int best_above_byte_saved = --best_above_byte;

	  while (best_above_byte > 0
		 && !CHAR_HEAD_P (XSTRING (string)->data[best_above_byte]))
	    best_above_byte--;
	  if (XSTRING (string)->data[best_above_byte] < 0x80)
	    best_above_byte = best_above_byte_saved;
	  best_above--;
	}
      i = best_above;
      i_byte = best_above_byte;
    }

  string_char_byte_cache_bytepos = i_byte;
  string_char_byte_cache_charpos = i;
  string_char_byte_cache_string = string;

  return i;
}

/* Convert STRING to a multibyte string.
   Single-byte characters 0240 through 0377 are converted
   by adding nonascii_insert_offset to each.  */

Lisp_Object
string_make_multibyte (string)
     Lisp_Object string;
{
  unsigned char *buf;
  int nbytes;

  if (STRING_MULTIBYTE (string))
    return string;

  nbytes = count_size_as_multibyte (XSTRING (string)->data,
				    XSTRING (string)->size);
  /* If all the chars are ASCII, they won't need any more bytes
     once converted.  In that case, we can return STRING itself.  */
  if (nbytes == STRING_BYTES (XSTRING (string)))
    return string;

  buf = (unsigned char *) alloca (nbytes);
  copy_text (XSTRING (string)->data, buf, STRING_BYTES (XSTRING (string)),
	     0, 1);

  return make_multibyte_string (buf, XSTRING (string)->size, nbytes);
}

/* Convert STRING to a single-byte string.  */

Lisp_Object
string_make_unibyte (string)
     Lisp_Object string;
{
  unsigned char *buf;

  if (! STRING_MULTIBYTE (string))
    return string;

  buf = (unsigned char *) alloca (XSTRING (string)->size);

  copy_text (XSTRING (string)->data, buf, STRING_BYTES (XSTRING (string)),
	     1, 0);

  return make_unibyte_string (buf, XSTRING (string)->size);
}

DEFUN ("string-make-multibyte", Fstring_make_multibyte, Sstring_make_multibyte,
       1, 1, 0,
  "Return the multibyte equivalent of STRING.")
  (string)
     Lisp_Object string;
{
  return string_make_multibyte (string);
}

DEFUN ("string-make-unibyte", Fstring_make_unibyte, Sstring_make_unibyte,
       1, 1, 0,
  "Return the unibyte equivalent of STRING.")
  (string)
     Lisp_Object string;
{
  return string_make_unibyte (string);
}

DEFUN ("string-as-unibyte", Fstring_as_unibyte, Sstring_as_unibyte,
       1, 1, 0,
  "Return a unibyte string with the same individual bytes as STRING.\n\
If STRING is unibyte, the result is STRING itself.")
  (string)
     Lisp_Object string;
{
  if (STRING_MULTIBYTE (string))
    {
      string = Fcopy_sequence (string);
      XSTRING (string)->size = STRING_BYTES (XSTRING (string));
    }
  return string;
}

DEFUN ("string-as-multibyte", Fstring_as_multibyte, Sstring_as_multibyte,
       1, 1, 0,
  "Return a multibyte string with the same individual bytes as STRING.\n\
If STRING is multibyte, the result is STRING itself.")
  (string)
     Lisp_Object string;
{
  if (! STRING_MULTIBYTE (string))
    {
      int newlen = multibyte_chars_in_text (XSTRING (string)->data,
					    STRING_BYTES (XSTRING (string)));
      /* If all the chars are ASCII, STRING is already suitable.  */
      if (newlen != STRING_BYTES (XSTRING (string)))
	{
	  string = Fcopy_sequence (string);
	  XSTRING (string)->size = newlen;
	}
    }
  return string;
}

DEFUN ("copy-alist", Fcopy_alist, Scopy_alist, 1, 1, 0,
  "Return a copy of ALIST.\n\
This is an alist which represents the same mapping from objects to objects,\n\
but does not share the alist structure with ALIST.\n\
The objects mapped (cars and cdrs of elements of the alist)\n\
are shared, however.\n\
Elements of ALIST that are not conses are also shared.")
  (alist)
     Lisp_Object alist;
{
  register Lisp_Object tem;

  CHECK_LIST (alist, 0);
  if (NILP (alist))
    return alist;
  alist = concat (1, &alist, Lisp_Cons, 0);
  for (tem = alist; CONSP (tem); tem = XCONS (tem)->cdr)
    {
      register Lisp_Object car;
      car = XCONS (tem)->car;

      if (CONSP (car))
	XCONS (tem)->car = Fcons (XCONS (car)->car, XCONS (car)->cdr);
    }
  return alist;
}

DEFUN ("substring", Fsubstring, Ssubstring, 2, 3, 0,
  "Return a substring of STRING, starting at index FROM and ending before TO.\n\
TO may be nil or omitted; then the substring runs to the end of STRING.\n\
If FROM or TO is negative, it counts from the end.\n\
\n\
This function allows vectors as well as strings.")
  (string, from, to)
     Lisp_Object string;
     register Lisp_Object from, to;
{
  Lisp_Object res;
  int size;
  int size_byte;
  int from_char, to_char;
  int from_byte, to_byte;

  if (! (STRINGP (string) || VECTORP (string)))
    wrong_type_argument (Qarrayp, string);

  CHECK_NUMBER (from, 1);

  if (STRINGP (string))
    {
      size = XSTRING (string)->size;
      size_byte = STRING_BYTES (XSTRING (string));
    }
  else
    size = XVECTOR (string)->size;

  if (NILP (to))
    {
      to_char = size;
      to_byte = size_byte;
    }
  else
    {
      CHECK_NUMBER (to, 2);

      to_char = XINT (to);
      if (to_char < 0)
	to_char += size;

      if (STRINGP (string))
	to_byte = string_char_to_byte (string, to_char);
    }

  from_char = XINT (from);
  if (from_char < 0)
    from_char += size;
  if (STRINGP (string))
    from_byte = string_char_to_byte (string, from_char);

  if (!(0 <= from_char && from_char <= to_char && to_char <= size))
    args_out_of_range_3 (string, make_number (from_char),
			 make_number (to_char));

  if (STRINGP (string))
    {
      res = make_multibyte_string (XSTRING (string)->data + from_byte,
				   to_char - from_char, to_byte - from_byte);
      copy_text_properties (from_char, to_char, string,
			    make_number (0), res, Qnil);
    }
  else
    res = Fvector (to_char - from_char,
		   XVECTOR (string)->contents + from_char);

  return res;
}

/* Extract a substring of STRING, giving start and end positions
   both in characters and in bytes.  */

Lisp_Object
substring_both (string, from, from_byte, to, to_byte)
     Lisp_Object string;
     int from, from_byte, to, to_byte;
{
  Lisp_Object res;
  int size;
  int size_byte;

  if (! (STRINGP (string) || VECTORP (string)))
    wrong_type_argument (Qarrayp, string);

  if (STRINGP (string))
    {
      size = XSTRING (string)->size;
      size_byte = STRING_BYTES (XSTRING (string));
    }
  else
    size = XVECTOR (string)->size;

  if (!(0 <= from && from <= to && to <= size))
    args_out_of_range_3 (string, make_number (from), make_number (to));

  if (STRINGP (string))
    {
      res = make_multibyte_string (XSTRING (string)->data + from_byte,
				   to - from, to_byte - from_byte);
      copy_text_properties (from, to, string, make_number (0), res, Qnil);
    }
  else
    res = Fvector (to - from,
		   XVECTOR (string)->contents + from);

  return res;
}

DEFUN ("nthcdr", Fnthcdr, Snthcdr, 2, 2, 0,
  "Take cdr N times on LIST, returns the result.")
  (n, list)
     Lisp_Object n;
     register Lisp_Object list;
{
  register int i, num;
  CHECK_NUMBER (n, 0);
  num = XINT (n);
  for (i = 0; i < num && !NILP (list); i++)
    {
      QUIT;
      list = Fcdr (list);
    }
  return list;
}

DEFUN ("nth", Fnth, Snth, 2, 2, 0,
  "Return the Nth element of LIST.\n\
N counts from zero.  If LIST is not that long, nil is returned.")
  (n, list)
     Lisp_Object n, list;
{
  return Fcar (Fnthcdr (n, list));
}

DEFUN ("elt", Felt, Selt, 2, 2, 0,
  "Return element of SEQUENCE at index N.")
  (sequence, n)
     register Lisp_Object sequence, n;
{
  CHECK_NUMBER (n, 0);
  while (1)
    {
      if (CONSP (sequence) || NILP (sequence))
	return Fcar (Fnthcdr (n, sequence));
      else if (STRINGP (sequence) || VECTORP (sequence)
	       || BOOL_VECTOR_P (sequence) || CHAR_TABLE_P (sequence))
	return Faref (sequence, n);
      else
	sequence = wrong_type_argument (Qsequencep, sequence);
    }
}

DEFUN ("member", Fmember, Smember, 2, 2, 0,
  "Return non-nil if ELT is an element of LIST.  Comparison done with `equal'.\n\
The value is actually the tail of LIST whose car is ELT.")
  (elt, list)
     register Lisp_Object elt;
     Lisp_Object list;
{
  register Lisp_Object tail;
  for (tail = list; !NILP (tail); tail = XCONS (tail)->cdr)
    {
      register Lisp_Object tem;
      tem = Fcar (tail);
      if (! NILP (Fequal (elt, tem)))