/* lex.l                                                -*- C++ -*-

Copyright (C) 1992, 1993, 1994, 1995 John W. Eaton

This file is part of Octave.

Octave 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.

Octave 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 CC; see the file COPYING.  If not, write to the Free
Software Foundation, 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

*/

%s TEXT_FCN
%s MATRIX

%{
#define SHORT_CIRCUIT_LOGICALS 1

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <cctype>
#include <cstring>

#include <strstream.h>

#include "SLStack.h"

// These would be alphabetical, but y.tab.h must be included before
// oct-gperf.h and y.tab.h must be included after token.h and the tree
// class declarations.  We can't include y.tab.h in oct-gperf.h
// because it may not be protected to allow it to be included multiple
// times.

#include "error.h"
#include "input.h"
#include "lex.h"
#include "toplev.h"
#include "parse.h"
#include "symtab.h"
#include "token.h"
#include "pt-base.h"
#include "pt-cmd.h"
#include "pt-const.h"
#include "pt-exp.h"
#include "pt-misc.h"
#include "pt-plot.h"
#include "user-prefs.h"
#include "utils.h"
#include "variables.h"
#include "y.tab.h"
#include "oct-gperf.h"

// Stack to hold tokens so that we can delete them when the parser is
// reset and avoid growing forever just because we are stashing some
// information.  This has to appear before lex.h is included, because
// one of the macros defined there uses token_stack.
static SLStack <token*> token_stack;

// Nonzero means we think we are looking at a set command.
static int doing_set = 0;

// GAG.  Stupid kludge so that [[1,2][3,4]] will work.
static do_comma_insert = 0;

// Brace level count.
static int braceflag = 0;

// Return transpose or start a string?
int quote_is_transpose = 0;

// Nonzero means we thing we are looking at the beginning of a
// function definition.
int beginning_of_function = 0;

// Nonzero means that we should convert spaces to a comma inside a
// matrix definition.
static int convert_spaces_to_comma = 1;

// Another context hack, this time for the plot command's `using',
// `title', and `with' keywords.
static int cant_be_identifier = 0;

#define BRACE 1
#define PAREN 2

// Did eat_whitespace() eat a space or tab, or a newline, or both?
#define ATE_SPACE_OR_TAB 1
#define ATE_NEWLINE 2

// Is the closest nesting level a square brace or a paren?
//
//  BRACE -> spaces are important (they can turn into commas)
//           new lines are important (they can turn into semicolons)
//
//  PAREN -> spaces and new lines are not important

static SLStack <int> nesting_level;

// Forward declarations for functions defined at the bottom of this
// file.

static void do_string_escapes (char *s);
static void fixup_column_count (char *s);
static void do_comma_insert_check (void);
static int is_plot_keyword (char *s);
static int is_keyword (char *s);
static char *plot_style_token (char *s);
static symbol_record *lookup_identifier (char *s);
static void grab_help_text (void);
static int match_any (char c, char *s);
static int next_token_is_bin_op (int spc_prev, char *yytext);
static int next_token_is_postfix_unary_op (int spc_prev, char *yytext);
static char *strip_trailing_whitespace (char *s);
static void handle_number (char *yytext);
static int handle_string (char delim, int text_style = 0);
static int handle_close_brace (int spc_gobbled);
static int handle_identifier (char *tok, int spc_gobbled);
static int have_continuation (int trailing_comments_ok = 1);
static int have_ellipsis_continuation (int trailing_comments_ok = 1);
static int eat_whitespace (void);
static int eat_continuation (void);

%}

D	[0-9]
S	[ \t]
NL	[\n]
SNL	[ \t\n]
EL	(\.\.\.)
BS	(\\)
CONT	({EL}|{BS})
Im	[iIjJ]
CCHAR	[#%]
COMMENT	({CCHAR}.*{NL})
SNLCMT	({SNL}|{COMMENT})
NOTEQ	((~=)|(!=)|(<>))
POW	((\*\*)|(\^))
EPOW	(\.{POW})
NOT	((\~)|(\!))
IDENT	([_a-zA-Z][_a-zA-Z0-9]*)
EXPON	([DdEe][+-]?{D}+)
NUMBER	(({D}+\.?{D}*{EXPON}?)|(\.{D}+{EXPON}?))
%%

%{
// Help and other text-style functions are a pain in the ass.  This
// stuff needs to be simplified.  May require some changes in the
// parser too.
%}

<TEXT_FCN>{NL} {
    BEGIN 0;
    current_input_column = 1;
    quote_is_transpose = 0;
    cant_be_identifier = 0;
    convert_spaces_to_comma = 1;
    return '\n';
  }

<TEXT_FCN>[\;\,] {
    if (doing_set && strcmp (yytext, ",") == 0)
      {
	TOK_PUSH_AND_RETURN (yytext, TEXT);
      }
    else
      {
	BEGIN 0;
	if (strcmp (yytext, ",") == 0)
	  TOK_RETURN (',');
	else
	  TOK_RETURN (';');
      }
  }

<TEXT_FCN>[\"\'] {
    current_input_column++;
    return handle_string (yytext[0], 1);
  }

<TEXT_FCN>[^ \t\n\;\,]*{S}* {
    char *tok = strip_trailing_whitespace (yytext);
    TOK_PUSH_AND_RETURN (tok, TEXT);
  }

%{
// For this and the next two rules, we're looking at ']', and we
// need to know if the next token is `=' or `=='.
//
// It would have been so much easier if the delimiters were simply
// different for the expression on the left hand side of the equals
// operator.
//
// It's also a pain in the ass to decide whether to insert a comma
// after seeing a ']' character...
%}

<MATRIX>{SNL}*\]{S}* {
    fixup_column_count (yytext);
    int c = yytext[yyleng-1];
    int cont_is_spc = eat_continuation ();
    int spc_gobbled = (cont_is_spc || c == ' ' || c == '\t');
    return handle_close_brace (spc_gobbled);
  }

%{
// Commas are element separators in matrix constants.  If we don't
// check for continuations here we can end up inserting too many
// commas.
%}

<MATRIX>{S}*\,{S}* {
    current_input_column += yyleng;
    int tmp = eat_continuation ();
    quote_is_transpose = 0;
    cant_be_identifier = 0;
    convert_spaces_to_comma = 1;
    if (user_pref.whitespace_in_literal_matrix != 2
	&& (tmp & ATE_NEWLINE) == ATE_NEWLINE)
      unput (';');
    return (',');
  }

%{
// In some cases, spaces in matrix constants can turn into commas.
// If commas are required, spaces are not important in matrix
// constants so we just eat them.  If we don't check for continuations
// here we can end up inserting too many commas.
%}

<MATRIX>{S}+ {
    current_input_column += yyleng;
    if (user_pref.whitespace_in_literal_matrix != 2)
      {
	int tmp = eat_continuation ();
	int bin_op = next_token_is_bin_op (1, yytext);
	int postfix_un_op = next_token_is_postfix_unary_op (1, yytext);

	if (! (postfix_un_op || bin_op || nesting_level.empty ())
	    && nesting_level.top () == BRACE
	    && convert_spaces_to_comma)
	  {
	    quote_is_transpose = 0;
	    cant_be_identifier = 0;
	    convert_spaces_to_comma = 1;
	    if ((tmp & ATE_NEWLINE) == ATE_NEWLINE)
	      unput (';');
	    return (',');
	  }
      }
  }

%{
// Semicolons are handled as row seprators in matrix constants.  If we
// don't eat whitespace here we can end up inserting too many
// semicolons.
%}

<MATRIX>{SNLCMT}*;{SNLCMT}* {
    fixup_column_count (yytext);
    eat_whitespace ();
    quote_is_transpose = 0;
    cant_be_identifier = 0;
    convert_spaces_to_comma = 1;
    return ';';
  }

%{
// In some cases, new lines can also become row separators.  If we
// don't eat whitespace here we can end up inserting too many
// semicolons.
%}

<MATRIX>{SNLCMT}*\n{SNLCMT}* {
    fixup_column_count (yytext);
    eat_whitespace ();
    if (user_pref.whitespace_in_literal_matrix != 2)
      {
	quote_is_transpose = 0;
	cant_be_identifier = 0;
	convert_spaces_to_comma = 1;

	if (nesting_level.empty ())
	  return LEXICAL_ERROR;

	if (nesting_level.top () == BRACE)
	  return ';';
      }
  }

%{
// Open and close brace are handled differently if we are in the range
// part of a plot command.
//
%}

\[{S}* {
    nesting_level.push (BRACE);

    current_input_column += yyleng;
    quote_is_transpose = 0;
    cant_be_identifier = 0;
    convert_spaces_to_comma = 1;

    promptflag--;
    eat_whitespace ();

    if (plotting && ! past_plot_range)
      {
	in_plot_range = 1;
	return OPEN_BRACE;
      }
    else
      {
	mlnm.push (1);
	braceflag++;
	BEGIN MATRIX;
	return '[';
      }
  }

\] {
    if (! nesting_level.empty ())
      nesting_level.pop ();

    if (plotting && ! past_plot_range)
      {
	in_plot_range = 0;
	TOK_RETURN (CLOSE_BRACE);
      }
    else
      TOK_RETURN (']');
  }

%{
// Imaginary numbers.
%}

{NUMBER}{Im} {
    handle_number (yytext);
    return IMAG_NUM;
  }

%{
// Real numbers.  Don't grab the `.' part of a dot operator as part of
// the constant.
%}

{D}+/\.[\*/\\^'] |
{NUMBER} {
    handle_number (yytext);
    return NUM;
  }

%{
// Eat whitespace.  Whitespace inside matrix constants is handled by
// the <MATRIX> start state code above.
%}

{S}* {
    current_input_column += yyleng;
  }

%{
// Continuation lines.  Allow comments after continuations.
%}

{CONT}{S}*{NL} |
{CONT}{S}*{COMMENT} {
    promptflag--;
    current_input_column = 1;
  }

%{
// An ellipsis not at the end of a line is not a continuation, but
// does have another meaning.
%}

{EL} {
    return ELLIPSIS;
  }

%{
// End of file.
%}

<<EOF>> {
    TOK_RETURN (END_OF_INPUT);
  }

%{
// Identifiers.  Truncate the token at the first space or tab but
// don't write directly on yytext.
%}

{IDENT}{S}* {
    char *tok = strip_trailing_whitespace (yytext);
    int c = yytext[yyleng-1];
    int cont_is_spc = eat_continuation ();
    int spc_gobbled = (cont_is_spc || c == ' ' || c == '\t');
    return handle_identifier (tok, spc_gobbled);
  }

%{
// A new line character.  New line characters inside matrix constants
// are handled by the <MATRIX> start state code above.  If closest
// nesting is inside parentheses, don't return a row separator.
%}

{NL} {
    quote_is_transpose = 0;
    cant_be_identifier = 0;
    current_input_column = 1;
    convert_spaces_to_comma = 1;

    if (nesting_level.empty ())
      return '\n';

    if (nesting_level.top () == BRACE)
      return LEXICAL_ERROR;
  }

%{
// Single quote can either be the beginning of a string or a transpose
// operator. 
%}

"'" {
    current_input_column++;
    convert_spaces_to_comma = 1;

    if (quote_is_transpose)
      {
	do_comma_insert_check ();
	return QUOTE;
      }
    else
      return handle_string ('\'');
  }

%{
// Double quotes always begin strings.
%}

\" {
    current_input_column++;
    return handle_string ('"');
}

%{
// The colon operator is handled differently if we are in the range
// part of a plot command.
%}

":" {
    if (plotting && (in_plot_range || in_plot_using))
      BIN_OP_RETURN (COLON, 1);
    else
      BIN_OP_RETURN (':', 0);
  }

%{
// Gobble comments.  If closest nesting is inside parentheses, don't
// return a new line.
%} 

{CCHAR} {
    if (! help_buf && beginning_of_function && nesting_level.empty ())
      {
	grab_help_text ();
	beginning_of_function = 0;
      }
    else
      {
	int c;
	while ((c = yyinput ()) != EOF && c != '\n')
	  ; // Eat comment.
      }

    quote_is_transpose = 0;
    cant_be_identifier = 0;
    current_input_column = 1;
    convert_spaces_to_comma = 1;

    if (nesting_level.empty ())
      return '\n';
    else if (nesting_level.top () == BRACE)
      return ';';
  }

%{
// Other operators.
%}

".+"		{ BIN_OP_RETURN (EPLUS, 0); }
".-"		{ BIN_OP_RETURN (EMINUS, 0); }
".*"		{ BIN_OP_RETURN (EMUL, 0); }
"./"		{ BIN_OP_RETURN (EDIV, 0); }
".\\"		{ BIN_OP_RETURN (ELEFTDIV, 0); }
{EPOW}		{ BIN_OP_RETURN (EPOW, 0); }
".'"		{ do_comma_insert_check (); BIN_OP_RETURN (TRANSPOSE, 1); }
"++"		{ do_comma_insert_check (); BIN_OP_RETURN (PLUS_PLUS, 1); }
"--"		{ do_comma_insert_check (); BIN_OP_RETURN (MINUS_MINUS, 1); }
"<="		{ BIN_OP_RETURN (EXPR_LE, 0); }
"=="		{ BIN_OP_RETURN (EXPR_EQ, 0); }
{NOTEQ}		{ BIN_OP_RETURN (EXPR_NE, 0); }
">="		{ BIN_OP_RETURN (EXPR_GE, 0); }
"|"		{ BIN_OP_RETURN (EXPR_OR, 0); }
"&"		{ BIN_OP_RETURN (EXPR_AND, 0); }
"<"		{ BIN_OP_RETURN (EXPR_LT, 0); }
">"		{ BIN_OP_RETURN (EXPR_GT, 0); }
"*"		{ BIN_OP_RETURN ('*', 0); }
"/"		{ BIN_OP_RETURN ('/', 0); }
"\\"		{ BIN_OP_RETURN (LEFTDIV, 0); }
";"		{ BIN_OP_RETURN (';', 1); }
","		{ BIN_OP_RETURN (',', 1); }
{POW}		{ BIN_OP_RETURN (POW, 0); }
"="		{ BIN_OP_RETURN ('=', 1); }

"||" {
#ifdef SHORT_CIRCUIT_LOGICALS
    BIN_OP_RETURN (EXPR_OR_OR, 0);
#else
    BIN_OP_RETURN (EXPR_OR, 0);
#endif
  }

"&&" {
#ifdef SHORT_CIRCUIT_LOGICALS
    BIN_OP_RETURN (EXPR_AND_AND, 0);
#else
    BIN_OP_RETURN (EXPR_AND, 0);
#endif
  }

{NOT} {
    if (plotting && ! in_plot_range)
      past_plot_range = 1;
    BIN_OP_RETURN (EXPR_NOT, 0);
  }

"+" { 
    if (plotting && ! in_plot_range)
      past_plot_range = 1;
    BIN_OP_RETURN ('+', 0);
  }

"-" { 
    if (plotting && ! in_plot_range)
      past_plot_range = 1;
    BIN_OP_RETURN ('-', 0);
  }

"(" {
    if (plotting && ! in_plot_range)
      past_plot_range = 1;
    nesting_level.push (PAREN);
    promptflag--;
    TOK_RETURN ('(');
  }

")" {
    if (! nesting_level.empty ())
      nesting_level.pop ();

    current_input_column++;
    cant_be_identifier = 1;
    quote_is_transpose = 1;
    convert_spaces_to_comma = (! nesting_level.empty ()
			       && nesting_level.top () == BRACE);
    do_comma_insert_check ();
    return ')';
  }

%{
// We return everything else as single character tokens, which should
// eventually result in a parse error.
%}

.		{ TOK_RETURN (yytext[0]); }

%%

// GAG.
//
// If we're reading a matrix and the next character is '[', make sure
// that we insert a comma ahead of it.

void
do_comma_insert_check (void)
{
  int spc_gobbled = eat_continuation ();
  int c = yyinput ();
  yyunput (c, yytext);
  if (spc_gobbled)
    yyunput (' ', yytext);
  do_comma_insert = (braceflag && c == '[');
}

// Fix things up for errors or interrupts.  The parser is never called
// recursively, so it is always safe to reinitialize its state before
// doing any parsing.

void
reset_parser (void)
{
// Start off on the right foot.
  BEGIN 0;
  error_state = 0;

// We do want a prompt by default.
  promptflag = 1;

// Not initially screwed by `function [...] = f (...)' syntax.
  maybe_screwed = 0;
  maybe_screwed_again = 0;

// Not initially inside a loop or if statement.
  looping = 0;
  iffing = 0;

// Quote marks strings intially.
  quote_is_transpose = 0;

// Next token can be identifier.
  cant_be_identifier = 0;

// No need to do comma insert or convert spaces to comma at beginning
// of input. 
  do_comma_insert = 0;
  convert_spaces_to_comma = 1;

// Not initially defining a function.
  beginning_of_function = 0;
  defining_func = 0;

// Not initially doing any plotting or setting of plot attributes.
  plotting = 0;
  in_plot_range = 0;
  past_plot_range = 0;
  in_plot_using = 0;
  in_plot_style = 0;
  doing_set = 0;

// Not initially looking at indirect references.
  looking_at_indirect_ref = 0;

// Error may have occurred inside some parentheses or braces.
  nesting_level.clear ();

// Not initially defining a matrix list.
  braceflag = 0;
  ml.clear ();
  mlnm.clear ();

// Clear out the stack of token info used to track line and column
// numbers.
  while (! token_stack.empty ())
    delete token_stack.pop ();

// Can be reset by defining a function.
  if (! (reading_script_file || reading_fcn_file))
    {
      current_input_column = 1;
      input_line_number = current_command_number - 1;
    }

// Only ask for input from stdin if we are expecting interactive
// input.
  if (interactive && ! (reading_fcn_file || get_input_from_eval_string))
    yyrestart (stdin);

// Delete the buffer for help text.
  delete [] help_buf;
  help_buf = 0;
}

// Replace backslash escapes in a string with the real values.

static void
do_string_escapes (char *s)
{
  char *p1 = s;
  char *p2 = s;
  while (*p2 != '\0')
    {
      if (*p2 == '\\' && *(p2+1) != '\0')
	{
	  switch (*++p2)
	    {
	    case 'a':
	      *p1 = '\a';
	      break;

	    case 'b': // backspace
	      *p1 = '\b';
	      break;

	    case 'f': // formfeed
	      *p1 = '\f';
	      break;

	    case 'n': // newline
	      *p1 = '\n';
	      break;

	    case 'r': // carriage return
	      *p1 = '\r';
	      break;

	    case 't': // horizontal tab
	      *p1 = '\t';
	      break;

	    case 'v': // vertical tab
	      *p1 = '\v';
	      break;

	    case '\\': // backslash
	      *p1 = '\\';
	      break;

	    case '\'': // quote
	      *p1 = '\'';
	      break;

	    case '"': // double quote
	      *p1 = '"';
	      break;

	    default:
	      warning ("unrecognized escape sequence `\\%c' --\
 converting to `%c'", *p2, *p2);
	      *p1 = *p2;
	      break;
	    }
	}
      else
	{
	  *p1 = *p2;
	}

      p1++;
      p2++;
    }

  *p1 = '\0';
}

// If we read some newlines, we need figure out what column we're
// really looking at.

static void
fixup_column_count (char *s)
{
  char c;
  while ((c = *s++) != '\0')
    {
      if (c == '\n')
	  current_input_column = 1;
      else
	current_input_column++;
    }
}

// Include these so that we don't have to link to libfl.a.

#ifdef yywrap
#undef yywrap
#endif
static int
yywrap (void)
{
  return 1;
}

// These are not needed with flex-2.4.6, but may be needed with
// earlier 2.4.x versions.

#if 0
static void *
yy_flex_alloc (int size)
{
  return (void *) malloc ((unsigned) size);
}

static void *
yy_flex_realloc (void *ptr, int size)
{
  return (void *) realloc (ptr, (unsigned) size);
}

static void
yy_flex_free (void *ptr)
{
  free (ptr);
}
#endif

// Tell us all what the current buffer is.

YY_BUFFER_STATE
current_buffer (void)
{
  return YY_CURRENT_BUFFER;
}

// Create a new buffer.

YY_BUFFER_STATE
create_buffer (FILE *f)
{
  return yy_create_buffer (f, YY_BUF_SIZE);
}

// Start reading a new buffer.

void
switch_to_buffer (YY_BUFFER_STATE buf)
{
  yy_switch_to_buffer (buf);
}

// Delete a buffer.

void
delete_buffer (YY_BUFFER_STATE buf)
{
  yy_delete_buffer (buf);
}

// Restore a buffer (for unwind-prot).

void
restore_input_buffer (void *buf)
{
  switch_to_buffer ((YY_BUFFER_STATE) buf);
}

// Delete a buffer (for unwind-prot).

void
delete_input_buffer (void *buf)
{
  delete_buffer ((YY_BUFFER_STATE) buf);
}

// Check to see if a character string matches any of the possible line
// styles for plots.

static char *
plot_style_token (char *s)
{
  static char *plot_styles[] = 
    {
      "boxes",
      "boxerrorbars",
      "dots",
      "errorbars",
      "impulses",
      "lines",
      "linespoints",
      "points",
      "steps",
      0,
    };

  char **tmp = plot_styles;
  while (*tmp)
    {
      if (almost_match (*tmp, s))
	return *tmp;

      tmp++;
    }

  return 0;
}

// Check to see if a character string matches any one of the plot
// option keywords.  Don't match abbreviations for clear, since that's
// not a gnuplot keyword (users will probably only expect to be able
// to abbreviate actual gnuplot keywords).

static int
is_plot_keyword (char *s)
{
  if (almost_match ("title", s))
    {
      return TITLE;
    }
  else if (almost_match ("using", s))
    {
      in_plot_using = 1;
      return USING;
    }
  else if (almost_match ("with", s))
    {
      in_plot_style = 1;
      return WITH;
    }
  else if (strcmp ("clear", s) == 0)
    {
      return CLEAR;
    }
  else
    {
      return 0;
    }
}

// Handle keywords.  Could probably be more efficient...

static int
is_keyword (char *s)
{
  if (plotting && in_plot_style)
    {
      char *sty = plot_style_token (s);
      if (sty)
	{
	  in_plot_style = 0;
	  yylval.tok_val = new token (sty);
	  token_stack.push (yylval.tok_val);
	  return STYLE;
	}
    }

  int l = input_line_number;
  int c = current_input_column;

  int len = strlen (s);

  const octave_kw *kw = octave_kw_lookup (s, len);

  if (kw)
    {
      yylval.tok_val = 0;

      switch (kw->kw_id)
	{
	case all_va_args_kw:
	case break_kw:
	case catch_kw:
	case continue_kw:
	case else_kw:
	case elseif_kw:
	case global_kw:
	case return_kw:
	case unwind_protect_cleanup_kw:
 	  break;

	case end_kw:
	  yylval.tok_val = new token (token::simple_end, l, c);
	  break;

	case end_try_catch_kw:
	  yylval.tok_val = new token (token::try_catch_end, l, c);
	  break;

	case end_unwind_protect_kw:
	  yylval.tok_val = new token (token::unwind_protect_end, l, c);
	  break;

	case endfor_kw:
	  yylval.tok_val = new token (token::for_end, l, c);
	  break;

	case endfunction_kw:
	  yylval.tok_val = new token (token::function_end, l, c);
	  break;

	case endif_kw:
	  yylval.tok_val = new token (token::if_end, l, c);
	  break;

	case endwhile_kw:
	  yylval.tok_val = new token (token::while_end, l, c);
	  break;

	case for_kw:
	case while_kw:
	  promptflag--;
	  looping++;
	  break;

	case if_kw:
	  iffing++;
	  promptflag--;
	  break;

	case try_kw:
	case unwind_protect_kw:
	  promptflag--;
	  break;

	case gplot_kw:
	  plotting = 1;
	  yylval.tok_val = new token (token::two_dee, l, c);
	  break;

	case gsplot_kw:
	  plotting = 1;
	  yylval.tok_val = new token (token::three_dee, l, c);
	  break;

	case replot_kw:
	  plotting = 1;
	  yylval.tok_val = new token (token::replot, l, c);
	  break;

	case function_kw:
	  if (defining_func)
	    {
	      error ("function keyword invalid within a function body");

	      if ((reading_fcn_file || reading_script_file)
		  && curr_fcn_file_name)
		error ("defining new function near line %d of file `%s.m'",
		       input_line_number, curr_fcn_file_name);
	      else
		error ("defining new function near line %d", input_line_number);

	      return LEXICAL_ERROR;
	    }
	  else
	    {
	      tmp_local_sym_tab = new symbol_table ();
	      curr_sym_tab = tmp_local_sym_tab;
	      defining_func = 1;
	      promptflag--;
	      beginning_of_function = 1;
	      if (! (reading_fcn_file || reading_script_file))
		input_line_number = 1;
	    }
	  break;

	default:
	  panic_impossible ();
	}

      if (! yylval.tok_val)
	yylval.tok_val = new token (l, c);

      token_stack.push (yylval.tok_val);

      return kw->tok;
    }

  return 0;
}

// Try to find an identifier.  All binding to global or builtin
// variables occurs when expressions are evaluated.

static symbol_record *
lookup_identifier (char *name)
{
  return curr_sym_tab->lookup (name, 1, 0);
}

// Grab the help text from an function file.  Always overwrites the
// current contents of help_buf.

static void
grab_help_text (void)
{
  delete [] help_buf;
  help_buf = 0;

  ostrstream buf;

  int in_comment = 1;
  int c = 0;

  while ((c = yyinput ()) != EOF)
    {
      if (in_comment)
	{
	  buf << (char) c;
	  if (c == '\n')
	    in_comment = 0;
	}
      else
	{
	  switch (c)
	    {
	    case '%':
	    case '#':
	      in_comment = 1;
	      break;

	    case ' ':
	    case '\t':
	      break;

	    default:
	      goto done;
	    }
	}
    }

 done:

  if (c)
    yyunput (c, yytext);

  buf << ends;

  help_buf = buf.str ();

  if (! help_buf || ! *help_buf)
    {
      delete [] help_buf;
      help_buf = 0;
    }
}

// Return 1 if the given character matches any character in the given
// string.

static int
match_any (char c, char *s)
{
  char tmp;
  while ((tmp = *s++) != '\0')
    {
      if (c == tmp)
	return 1;
    }
  return 0;
}

// Given information about the spacing surrounding an operator,
// return 1 if it looks like it should be treated as a binary
// operator.  For example,
//
//   [ 1 + 2 ]  or  [ 1+ 2]  or  [ 1+2 ]  ==> binary

static int
looks_like_bin_op (int spc_prev, int spc_next)
{
  return ((spc_prev && spc_next) || ! spc_prev);
}

// Duh.  This seems to no longer be needed.
#if 0
static int
next_char_is_space (void)
{
  int c = yyinput ();
  yyunput (c, yytext);
  return (c == ' ' || c == '\t');
}
#endif

// Try to determine if the next token should be treated as a postfix
// unary operator.  This is ugly, but it seems to do the right thing.

static int
next_token_is_postfix_unary_op (int spc_prev, char *yytext)
{
  int un_op = 0;

  int c0 = yyinput ();
  int c1 = yyinput ();

  yyunput (c1, yytext);
  yyunput (c0, yytext);

  int transpose = (c0 == '.' && c1 == '\'');
  int hermitian = (c0 == '\'');

  un_op = (transpose || (hermitian && ! spc_prev));

  return un_op;
}

// Try to determine if the next token should be treated as a binary
// operator.  This is even uglier, but it also seems to do the right
// thing.  Note that it is only necessary to check the spacing for `+'
// and `-', since those are the only tokens that can appear as unary
// ops too.
//
// Note that this never returns true for `.', even though it can be a
// binary operator (the structure reference thing).  The only time
// this appears to matter is for things like
//
//   [ a . b ]
//
// which probably doesn't occur that often, can be worked around by
// eliminating the whitespace, putting the expression in parentheses,
// or using `whitespace_in_literal_matrix = "ignored"', so I think it
// is an acceptable change.  It would be quite a bit harder to `fix'
// this.  (Well, maybe not.  the best fix would be to do away with the
// specialness of whitespace inside of `[ ... ]').
//
// However, we still do check for `.+', `.*', etc.

static int
next_token_is_bin_op (int spc_prev, char *yytext)
{
  int bin_op = 0;

  int c0 = yyinput ();

  switch (c0)
    {
    case '+':
    case '-':
      {
	int c1 = yyinput ();
	yyunput (c1, yytext);
	int spc_next = (c1 == ' ' || c1 == '\t');
	bin_op = looks_like_bin_op (spc_prev, spc_next);
      }
      break;

    case '.':
      {
	int c1 = yyinput ();
	yyunput (c1, yytext);
	bin_op = match_any (c1, "+-*/\\^");
      }
      break;

    case '/':
    case ':':
    case '\\':
    case '^':
    case '&':
    case '*':
    case '|':
    case '<':
    case '>':
    case '~':
    case '!':
    case '=':
      bin_op = 1;
      break;

    default:
      break;
    }

  yyunput (c0, yytext);

  return bin_op;
}

// Used to delete trailing white space from tokens.

static char *
strip_trailing_whitespace (char *s)
{
  static char *retval = 0;

  delete [] retval;

  retval = strsave (s);

  char *t = strchr (retval, ' ');
  if (t)
    *t = '\0';

  t = strchr (retval, '\t');
  if (t)
    *t = '\0';

  return retval;
}

// Discard whitespace, including comments and continuations.
//
// Return value is logical OR of the following values:
//
//  ATE_SPACE_OR_TAB : space or tab in input
//  ATE_NEWLINE      : bare new line in input

static int
eat_whitespace (void)
{
  int retval = 0;
  int in_comment = 0;
  int c;
  while ((c = yyinput ()) != EOF)
    {
      current_input_column++;

      switch (c)
	{
	case ' ':
	case '\t':
	  retval |= ATE_SPACE_OR_TAB;
	  break;

	case '\n':
	  retval |= ATE_NEWLINE;
	  in_comment = 0;
	  current_input_column = 0;
	  break;

	case '#':
	case '%':
	  in_comment = 1;
	  break;

	case '.':
	  if (in_comment)
	    break;
	  else
	    {
	      if (have_ellipsis_continuation ())
		break;
	      else
		goto done;
	    }

	case '\\':
	  if (in_comment)
	    break;
	  else
	    {
	      if (have_continuation ())
		break;
	      else
		goto done;
	    }

	default:
	  if (in_comment)
	    break;
	  else
	    goto done;
	}
    }

 done:
  yyunput (c, yytext);
  current_input_column--;
  return retval;
}

static void
handle_number (char *yytext)
{
  double value;
  int nread = sscanf (yytext, "%lf", &value);

// If yytext doesn't contain a valid number, we are in deep doo doo.

  assert (nread == 1);

  quote_is_transpose = 1;
  cant_be_identifier = 1;
  convert_spaces_to_comma = 1;

  if (plotting && ! in_plot_range)
    past_plot_range = 1;

  yylval.tok_val = new token (value, yytext, input_line_number,
			      current_input_column);

  token_stack.push (yylval.tok_val);

  current_input_column += yyleng;

  do_comma_insert_check ();
}

// We have seen a backslash and need to find out if it should be
// treated as a continuation character.  If so, this eats it, up to
// and including the new line character.
//
// Match whitespace only, followed by a comment character or newline.
// Once a comment character is found, discard all input until newline.
// If non-whitespace characters are found before comment
// characters, return 0.  Otherwise, return 1.

static int
have_continuation (int trailing_comments_ok)
{
  ostrstream buf;

  int in_comment = 0;
  char c;
  while ((c = yyinput ()) != EOF)
    {
      buf << (char) c;

      switch (c)
	{
	case ' ':
	case '\t':
	  break;

	case '%':
	case '#':
	  if (trailing_comments_ok)
	    in_comment = 1;
	  else
	    goto cleanup;
	  break;

	case '\n':
	  current_input_column = 0;
	  promptflag--;
	  return 1;

	default:
	  if (! in_comment)
	    goto cleanup;
	  break;
	}
    }

  yyunput (c, yytext);
  return 0;

 cleanup:
  buf << ends;
  char *s = buf.str ();
  if (s)
    {
      int len = strlen (s);
      while (len--)
	yyunput (s[len], yytext);
    }
  delete [] s;
  return 0;
}

// We have seen a `.' and need to see if it is the start of a
// continuation.  If so, this eats it, up to and including the new
// line character.

static int
have_ellipsis_continuation (int trailing_comments_ok)
{
  char c1 = yyinput ();
  if (c1 == '.')
    {
      char c2 = yyinput ();
      if (c2 == '.' && have_continuation (trailing_comments_ok))
	return 1;
      else
	{
	  yyunput (c2, yytext);
	  yyunput (c1, yytext);
	}
    }
  else
    yyunput (c1, yytext);

  return 0;
}

// See if we have a continuation line.  If so, eat it and the leading
// whitespace on the next line.
//
// Return value is the same as described for eat_whitespace().

static int
eat_continuation (void)
{
  int retval = 0;
  int c = yyinput ();
  if ((c == '.' && have_ellipsis_continuation ())
      || (c == '\\' && have_continuation ()))
    retval = eat_whitespace ();
  else
    yyunput (c, yytext);

  return retval;
}

static int
handle_string (char delim, int text_style)
{
  ostrstream buf;

  int c;
  int escape_pending = 0;

  while ((c = yyinput ()) != EOF)
    {
      current_input_column++;

      if (c == '\\')
	{
	  if (escape_pending)
	    {
	      buf << (char) c;
	      escape_pending = 0;
	    }
	  else
	    {
	      if (have_continuation (0))
		escape_pending = 0;
	      else
		{
		  buf << (char) c;
		  escape_pending = 1;
		}
	    }
	  continue;
	}
      else if (c == '.')
	{
	  if (! have_ellipsis_continuation (0))
	    buf << (char) c;
	}
      else if (c == '\n')
	{
	  error ("unterminated string constant");
	  break;
	}
      else if (c == delim)
	{
	  if (escape_pending)
	    buf << (char) c;
	  else
	    {
	      c = yyinput ();
	      if (c == delim)
		buf << (char) c;
	      else
		{
		  yyunput (c, yytext);
		  buf << ends;
		  char *tok = buf.str ();
		  do_string_escapes (tok);

		  if (text_style && doing_set)
		    {
		      if (tok)
			{
			  int len = strlen (tok) + 3;
			  char *tmp = tok;
			  tok = new char [len];
			  tok[0] = delim;
			  strcpy (tok+1, tmp);
			  tok[len-2] = delim;
			  tok[len-1] = '\0';
			  delete [] tmp;
			}
		    }
		  else
		    {
		      quote_is_transpose = 1;
		      cant_be_identifier = 1;
		      convert_spaces_to_comma = 1;
		    }

		  yylval.tok_val = new token (tok);
		  delete [] tok;
		  token_stack.push (yylval.tok_val);
		  return TEXT;
		}
	    }
	}
      else
	{
	  buf << (char) c;
	}

      escape_pending = 0;
    }

  return LEXICAL_ERROR;
}

static int
handle_close_brace (int spc_gobbled)
{
  if (! nesting_level.empty ())
    {
      nesting_level.pop ();
      braceflag--;
    }

  if (braceflag == 0)
    BEGIN 0;

  int c1 = yyinput ();
  if (c1 == '=')
    {
      quote_is_transpose = 0;
      cant_be_identifier = 0;
      convert_spaces_to_comma = 1;

      int c2 = yyinput ();
      unput (c2);
      unput (c1);

      if (c2 != '=' && maybe_screwed_again)
	return SCREW_TWO;
      else
	return ']';
    }
  else
    {
      unput (c1);

      if (braceflag && user_pref.whitespace_in_literal_matrix != 2)
	{
	  int bin_op = next_token_is_bin_op (spc_gobbled, yytext);
	  int postfix_un_op = next_token_is_postfix_unary_op
	    (spc_gobbled, yytext);

	  int other_op = match_any (c1, ",;\n]");

	  if (! (postfix_un_op || bin_op || other_op
		 || nesting_level.empty ())
	      && nesting_level.top () == BRACE
	      && convert_spaces_to_comma)
	    {
	      unput (',');
	      return ']';
	    }
	}
    }

  quote_is_transpose = 1;
  cant_be_identifier = 0;
  convert_spaces_to_comma = 1;
  return ']';
}

static void
maybe_unput_comma (int spc_gobbled)
{
  if (user_pref.whitespace_in_literal_matrix != 2
      && ! nesting_level.empty ()
      && nesting_level.top () == BRACE) 
    {
      int bin_op = next_token_is_bin_op (spc_gobbled, yytext);

      int postfix_un_op = next_token_is_postfix_unary_op (spc_gobbled,
							  yytext);

      int c1 = yyinput ();
      int c2 = yyinput ();
      unput (c2);
      unput (c1);
      int sep_op = match_any (c1, ",;\n]");
      int dot_op = (c1 == '.'
		    && (isalpha (c2) || isspace (c2) || c2 == '_'));
      int index_op = (c1 == '('
		      && (user_pref.whitespace_in_literal_matrix == 0
			  || ! spc_gobbled));

      if (! (postfix_un_op || bin_op || sep_op || dot_op || index_op))
	unput (',');
    }
}

// Figure out exactly what kind of token to return when we have seen
// an identifier.  Handles keywords.

static int
handle_identifier (char *tok, int spc_gobbled)
{
// It is almost always an error for an identifier to be followed
// directly by another identifier.  Special cases are handled below.

  cant_be_identifier = 1;

// If we are expecting a structure element, we just want to return
// TEXT_ID, which is a string that is also a valid identifier.  But
// first, we have to decide whether to insert a comma.

  if (looking_at_indirect_ref)
    {
      maybe_unput_comma (spc_gobbled);
      TOK_PUSH_AND_RETURN (tok, TEXT_ID);
    }

// If we have a regular keyword, or a plot STYLE, return it.  Keywords
// can be followed by identifiers (TOK_RETURN handles that).

  int kw_token = is_keyword (tok);
  if (kw_token)
    {
      if (kw_token == STYLE)
	{
	  current_input_column += yyleng;
	  quote_is_transpose = 0;
	  convert_spaces_to_comma = 1;
	  return kw_token;
	}
      else
	TOK_RETURN (kw_token);
    }

// See if we have a plot keyword (title, using, with, or clear).

  if (plotting)
    {
// Yes, we really do need both of these plot_range variables.  One
// is used to mark when we are past all possiblity of a plot range,
// the other is used to mark when we are actually between the square
// brackets that surround the range.

      if (! in_plot_range)
	past_plot_range = 1;

      // Option keywords can't appear in parentheses or braces.

      int plot_option_kw = 0;
      if (nesting_level.empty ())
	plot_option_kw = is_plot_keyword (tok);

      if (cant_be_identifier && plot_option_kw)
	TOK_RETURN (plot_option_kw);
    }

// If we are looking at a text style function, set up to gobble its
// arguments.  These are also reserved words, but only because it
// would be very difficult to do anything intelligent with them if
// they were not reserved.

  if (is_text_function_name (tok))
    {
      BEGIN TEXT_FCN;

      if (strcmp (tok, "set") == 0)
	doing_set = 1;
    }

  int c = yyinput ();
  yyunput (c, yytext);
  int next_tok_is_eq = (c == '=');

// Make sure we put the return values of a function in the symbol
// table that is local to the function.

  if (next_tok_is_eq && defining_func && maybe_screwed)
    curr_sym_tab = tmp_local_sym_tab;

// Find the token in the symbol table.

  yylval.tok_val = new token (lookup_identifier (tok),
			      input_line_number,
			      current_input_column);

  token_stack.push (yylval.tok_val);

// After seeing an identifer, it is ok to convert spaces to a comma
// (if needed).

  convert_spaces_to_comma = 1;

// If we are defining a function and we have not seen the parameter
// list yet and the next token is `=', return a token that represents
// the only return value for the function.  For example,
//
//   function SCREW = f (args);
//
// The variable maybe_screwed is reset in parse.y.

  if (next_tok_is_eq)
    {
      current_input_column += yyleng;
      if (defining_func && maybe_screwed)
	return SCREW;
      else
	return NAME;
    }

// At this point, we are only dealing with identifiers that are not
// followed by `=' (if the next token is `=', there is no need to
// check to see if we should insert a comma (invalid syntax), or allow
// a following `'' to be treated as a transpose (the next token is
// `=', so it can't be `''.

  quote_is_transpose = 1;
  do_comma_insert_check ();

  maybe_unput_comma (spc_gobbled);

  current_input_column += yyleng;
  return NAME;
}

// Print a warning if a function file that defines a function has
// anything other than comments and whitespace following the END token
// that matches the FUNCTION statement.

void
check_for_garbage_after_fcn_def (void)
{
// By making a newline be the next character to be read, we will force
// the parser to return after reading the function.  Calling yyunput
// with EOF seems not to work...

  int in_comment = 0;
  int lineno = input_line_number;
  int c;
  while ((c = yyinput ()) != EOF)
    {
      switch (c)
	{
	case ' ':
	case '\t':
	case ';':
	case ',':
	  break;

	case '\n':
	  if (in_comment)
	    in_comment = 0;
	  break;

	case '%':
	case '#':
	  in_comment = 1;
	  break;

	default:
	  if (in_comment)
	    break;
	  else
	    {
	      warning ("ignoring trailing garbage after end of function\n\
         near line %d of file `%s.m'", lineno, curr_fcn_file_name);
	      
	      yyunput ('\n', yytext);
	      return;
	    }
	}
    }
  yyunput ('\n', yytext);
}

/*

Maybe someday...

"+="		return ADD_EQ;
"-="		return SUB_EQ;
"*="		return MUL_EQ;
"/="		return DIV_EQ;
"\\="		return LEFTDIV_EQ;
".+="		return ADD_EQ;
".-="		return SUB_EQ;
".*="		return EMUL_EQ;
"./="		return EDIV_EQ;
".\\="		return ELEFTDIV_EQ;

*/