/*

Copyright (C) 1996, 1997 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 Octave; see the file COPYING.  If not, write to the Free
Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301, USA.

*/

// Parser for Octave.

// C decarations.

%{
#define YYDEBUG 1

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

#include <cassert>
#include <cstdio>

#ifdef YYBYACC
#include <cstdlib>
#endif

#include <map>
#include <sstream>

#include "Cell.h"
#include "Matrix.h"
#include "cmd-edit.h"
#include "cmd-hist.h"
#include "file-ops.h"
#include "file-stat.h"
#include "oct-env.h"
#include "oct-time.h"
#include "quit.h"

#include "comment-list.h"
#include "defaults.h"
#include "defun.h"
#include "dirfns.h"
#include "dynamic-ld.h"
#include "error.h"
#include "input.h"
#include "lex.h"
#include "load-path.h"
#include "oct-hist.h"
#include "oct-map.h"
#include "ov-fcn-handle.h"
#include "ov-usr-fcn.h"
#include "toplev.h"
#include "pager.h"
#include "parse.h"
#include "pt-all.h"
#include "symtab.h"
#include "token.h"
#include "unwind-prot.h"
#include "utils.h"
#include "variables.h"

// Temporary symbol table pointer used to cope with bogus function syntax.
symbol_table *tmp_local_sym_tab = 0;

// The current input line number.
int input_line_number = 0;

// The column of the current token.
int current_input_column = 1;

// Buffer for help text snagged from function files.
std::stack<std::string> help_buf;

// Buffer for comments appearing before a function statement.
static std::string fcn_comment_header;

// TRUE means we are using readline.
// (--no-line-editing)
bool line_editing = true;

// TRUE means we printed messages about reading startup files.
bool reading_startup_message_printed = false;

// TRUE means input is coming from startup file.
bool input_from_startup_file = false;

// TRUE means that we are in the process of evaluating a function
// body.  The parser might be called in that case if we are looking at
// an eval() statement.
bool evaluating_function_body = false;

// Keep a count of how many END tokens we expect.
int end_tokens_expected = 0;

// Keep track of symbol table information when parsing functions.
std::stack<symbol_table*> symtab_context;

// Name of parent function when parsing function files that might
// contain nested functions.
std::string parent_function_name;

// TRUE means we are in the process of autoloading a function.
static bool autoloading = false;

// TRUE means the current function file was found in a relative path
// element.
static bool fcn_file_from_relative_lookup = false;

// List of autoloads (function -> file mapping).
static std::map<std::string, std::string> autoload_map;

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

// Generic error messages.
static void
yyerror (const char *s);

// Error mesages for mismatched end tokens.
static void
end_error (const char *type, token::end_tok_type ettype, int l, int c);

// Check to see that end tokens are properly matched.
static bool
end_token_ok (token *tok, token::end_tok_type expected);

// Maybe print a warning if an assignment expression is used as the
// test in a logical expression.
static void
maybe_warn_assign_as_truth_value (tree_expression *expr);

// Maybe print a warning about switch labels that aren't constants.
static void
maybe_warn_variable_switch_label (tree_expression *expr);

// Finish building a range.
static tree_expression *
finish_colon_expression (tree_colon_expression *e);

// Build a constant.
static tree_constant *
make_constant (int op, token *tok_val);

// Build a function handle.
static tree_fcn_handle *
make_fcn_handle (token *tok_val);

// Build an anonymous function handle.
static tree_anon_fcn_handle *
make_anon_fcn_handle (tree_parameter_list *param_list, tree_statement *stmt);

// Build a binary expression.
static tree_expression *
make_binary_op (int op, tree_expression *op1, token *tok_val,
		tree_expression *op2);

// Build a boolean expression.
static tree_expression *
make_boolean_op (int op, tree_expression *op1, token *tok_val,
		 tree_expression *op2);

// Build a prefix expression.
static tree_expression *
make_prefix_op (int op, tree_expression *op1, token *tok_val);

// Build a postfix expression.
static tree_expression *
make_postfix_op (int op, tree_expression *op1, token *tok_val);

// Build an unwind-protect command.
static tree_command *
make_unwind_command (token *unwind_tok, tree_statement_list *body,
		     tree_statement_list *cleanup, token *end_tok,
		     octave_comment_list *lc, octave_comment_list *mc);

// Build a try-catch command.
static tree_command *
make_try_command (token *try_tok, tree_statement_list *body,
		  tree_statement_list *cleanup, token *end_tok,
		  octave_comment_list *lc, octave_comment_list *mc);

// Build a while command.
static tree_command *
make_while_command (token *while_tok, tree_expression *expr,
		    tree_statement_list *body, token *end_tok,
		    octave_comment_list *lc);

// Build a do-until command.
static tree_command *
make_do_until_command (token *do_tok, tree_statement_list *body,
		       tree_expression *expr, octave_comment_list *lc);

// Build a for command.
static tree_command *
make_for_command (token *for_tok, tree_argument_list *lhs,
		  tree_expression *expr, tree_statement_list *body,
		  token *end_tok, octave_comment_list *lc);

// Build a break command.
static tree_command *
make_break_command (token *break_tok);

// Build a continue command.
static tree_command *
make_continue_command (token *continue_tok);

// Build a return command.
static tree_command *
make_return_command (token *return_tok);

// Start an if command.
static tree_if_command_list *
start_if_command (tree_expression *expr, tree_statement_list *list);

// Finish an if command.
static tree_if_command *
finish_if_command (token *if_tok, tree_if_command_list *list,
		   token *end_tok, octave_comment_list *lc);

// Build an elseif clause.
static tree_if_clause *
make_elseif_clause (tree_expression *expr, tree_statement_list *list,
		    octave_comment_list *lc);

// Finish a switch command.
static tree_switch_command *
finish_switch_command (token *switch_tok, tree_expression *expr,
		       tree_switch_case_list *list, token *end_tok,
		       octave_comment_list *lc);

// Build a switch case.
static tree_switch_case *
make_switch_case (tree_expression *expr, tree_statement_list *list,
		  octave_comment_list *lc);

// Build an assignment to a variable.
static tree_expression *
make_assign_op (int op, tree_argument_list *lhs, token *eq_tok,
		tree_expression *rhs);

// Begin defining a function.
static octave_user_function *
start_function (tree_parameter_list *param_list, tree_statement_list *body);

// Do most of the work for defining a function.
static octave_user_function *
frob_function (const std::string& fname, octave_user_function *fcn);

// Finish defining a function.
static octave_user_function *
finish_function (tree_identifier *id, octave_user_function *fcn,
		 octave_comment_list *lc);

// Finish defining a function a different way.
static octave_user_function *
finish_function (tree_parameter_list *ret_list,
		 octave_user_function *fcn, octave_comment_list *lc);

// Reset state after parsing function.
static void
recover_from_parsing_function (void);

// Make an index expression.
static tree_index_expression *
make_index_expression (tree_expression *expr,
		       tree_argument_list *args, char type);

// Make an indirect reference expression.
static tree_index_expression *
make_indirect_ref (tree_expression *expr, const std::string&);

// Make an indirect reference expression with dynamic field name.
static tree_index_expression *
make_indirect_ref (tree_expression *expr, tree_expression *field);

// Make a declaration command.
static tree_decl_command *
make_decl_command (int tok, token *tok_val, tree_decl_init_list *lst);

// Finish building a matrix list.
static tree_expression *
finish_matrix (tree_matrix *m);

// Finish building a cell list.
static tree_expression *
finish_cell (tree_cell *c);

// Maybe print a warning.  Duh.
static void
maybe_warn_missing_semi (tree_statement_list *);

// Set the print flag for a statement based on the separator type.
static void
set_stmt_print_flag (tree_statement_list *, char, bool);

#define ABORT_PARSE \
  do \
    { \
      global_command = 0; \
      yyerrok; \
      if (! symtab_context.empty ()) \
        { \
	  curr_sym_tab = symtab_context.top (); \
	  symtab_context.pop (); \
        } \
      if (interactive || forced_interactive) \
	YYACCEPT; \
      else \
	YYABORT; \
    } \
  while (0)

%}

// Bison declarations.

// Don't add spaces around the = here; it causes some versions of
// bison to fail to properly recognize the directive.

%name-prefix="octave_"

%union
{
  // The type of the basic tokens returned by the lexer.
  token *tok_val;

  // Comment strings that we need to deal with mid-rule.
  octave_comment_list *comment_type;

  // Types for the nonterminals we generate.
  char sep_type;
  tree *tree_type;
  tree_matrix *tree_matrix_type;
  tree_cell *tree_cell_type;
  tree_expression *tree_expression_type;
  tree_constant *tree_constant_type;
  tree_fcn_handle *tree_fcn_handle_type;
  tree_anon_fcn_handle *tree_anon_fcn_handle_type;
  tree_identifier *tree_identifier_type;
  tree_index_expression *tree_index_expression_type;
  tree_colon_expression *tree_colon_expression_type;
  tree_argument_list *tree_argument_list_type;
  tree_parameter_list *tree_parameter_list_type;
  tree_command *tree_command_type;
  tree_if_command *tree_if_command_type;
  tree_if_clause *tree_if_clause_type;
  tree_if_command_list *tree_if_command_list_type;
  tree_switch_command *tree_switch_command_type;
  tree_switch_case *tree_switch_case_type;
  tree_switch_case_list *tree_switch_case_list_type;
  tree_decl_elt *tree_decl_elt_type;
  tree_decl_init_list *tree_decl_init_list_type;
  tree_decl_command *tree_decl_command_type;
  tree_statement *tree_statement_type;
  tree_statement_list *tree_statement_list_type;
  octave_user_function *octave_user_function_type;
}

// Tokens with line and column information.
%token <tok_val> '=' ':' '-' '+' '*' '/'
%token <tok_val> ADD_EQ SUB_EQ MUL_EQ DIV_EQ LEFTDIV_EQ POW_EQ
%token <tok_val> EMUL_EQ EDIV_EQ ELEFTDIV_EQ EPOW_EQ AND_EQ OR_EQ
%token <tok_val> LSHIFT_EQ RSHIFT_EQ LSHIFT RSHIFT
%token <tok_val> EXPR_AND_AND EXPR_OR_OR
%token <tok_val> EXPR_AND EXPR_OR EXPR_NOT
%token <tok_val> EXPR_LT EXPR_LE EXPR_EQ EXPR_NE EXPR_GE EXPR_GT
%token <tok_val> LEFTDIV EMUL EDIV ELEFTDIV EPLUS EMINUS
%token <tok_val> QUOTE TRANSPOSE
%token <tok_val> PLUS_PLUS MINUS_MINUS POW EPOW
%token <tok_val> NUM IMAG_NUM
%token <tok_val> STRUCT_ELT
%token <tok_val> NAME
%token <tok_val> END
%token <tok_val> DQ_STRING SQ_STRING
%token <tok_val> FOR WHILE DO UNTIL
%token <tok_val> IF ELSEIF ELSE
%token <tok_val> SWITCH CASE OTHERWISE
%token <tok_val> BREAK CONTINUE FUNC_RET
%token <tok_val> UNWIND CLEANUP
%token <tok_val> TRY CATCH
%token <tok_val> GLOBAL STATIC
%token <tok_val> FCN_HANDLE

// Other tokens.
%token END_OF_INPUT LEXICAL_ERROR
%token FCN VARARGIN VARARGOUT
%token CLOSE_BRACE

// Nonterminals we construct.
%type <comment_type> stash_comment function_beg
%type <sep_type> sep_no_nl opt_sep_no_nl sep opt_sep
%type <tree_type> input
%type <tree_constant_type> string constant magic_colon
%type <tree_anon_fcn_handle_type> anon_fcn_handle
%type <tree_fcn_handle_type> fcn_handle
%type <tree_matrix_type> matrix_rows matrix_rows1
%type <tree_cell_type> cell_rows cell_rows1
%type <tree_expression_type> matrix cell
%type <tree_expression_type> primary_expr postfix_expr prefix_expr binary_expr
%type <tree_expression_type> simple_expr colon_expr assign_expr expression
%type <tree_identifier_type> identifier fcn_name
%type <octave_user_function_type> function1 function2 function3
%type <tree_index_expression_type> word_list_cmd
%type <tree_colon_expression_type> colon_expr1
%type <tree_argument_list_type> arg_list word_list assign_lhs
%type <tree_argument_list_type> cell_or_matrix_row
%type <tree_parameter_list_type> param_list param_list1 param_list2
%type <tree_parameter_list_type> return_list return_list1
%type <tree_command_type> command select_command loop_command
%type <tree_command_type> jump_command except_command function
%type <tree_if_command_type> if_command
%type <tree_if_clause_type> elseif_clause else_clause
%type <tree_if_command_list_type> if_cmd_list1 if_cmd_list
%type <tree_switch_command_type> switch_command
%type <tree_switch_case_type> switch_case default_case
%type <tree_switch_case_list_type> case_list1 case_list
%type <tree_decl_elt_type> decl2
%type <tree_decl_init_list_type> decl1
%type <tree_decl_command_type> declaration
%type <tree_statement_type> statement
%type <tree_statement_list_type> simple_list simple_list1 list list1
%type <tree_statement_list_type> opt_list input1 function4

// Precedence and associativity.
%left ';' ',' '\n'
%right '=' ADD_EQ SUB_EQ MUL_EQ DIV_EQ LEFTDIV_EQ POW_EQ EMUL_EQ EDIV_EQ ELEFTDIV_EQ EPOW_EQ OR_EQ AND_EQ LSHIFT_EQ RSHIFT_EQ
%left EXPR_OR_OR
%left EXPR_AND_AND
%left EXPR_OR
%left EXPR_AND
%left EXPR_LT EXPR_LE EXPR_EQ EXPR_NE EXPR_GE EXPR_GT
%left LSHIFT RSHIFT
%left ':'
%left '-' '+' EPLUS EMINUS
%left '*' '/' LEFTDIV EMUL EDIV ELEFTDIV
%left UNARY PLUS_PLUS MINUS_MINUS EXPR_NOT
%left POW EPOW QUOTE TRANSPOSE
%left '(' '.' '{'

// Where to start.
%start input

%%

// ==============================
// Statements and statement lists
// ==============================

input		: input1
		  {
		    global_command = $1;
		    promptflag = 1;
		    YYACCEPT;
		  }
		| simple_list parse_error
		  { ABORT_PARSE; }
		| parse_error
		  { ABORT_PARSE; }
		;

input1		: '\n'
		  { $$ = 0; }
		| END_OF_INPUT
		  {
		    parser_end_of_input = 1;
		    $$ = 0;
		  }
		| simple_list
		  { $$ = $1; }
		| simple_list '\n'
		  { $$ = $1; }
		| simple_list END_OF_INPUT
		  { $$ = $1; }
		;

simple_list	: simple_list1 opt_sep_no_nl
		  {
		    set_stmt_print_flag ($1, $2, false);
		    $$ = $1;
		  }
		;

simple_list1	: statement
		  { $$ = new tree_statement_list ($1); }
		| simple_list1 sep_no_nl statement
		  {
		    set_stmt_print_flag ($1, $2, false);
		    $1->append ($3);
		    $$ = $1;
		  }
		;

opt_list	: // empty
		  { $$ = new tree_statement_list (); }
		| list
		  { $$ = $1; }
		;

list		: list1 opt_sep
		  {
		    set_stmt_print_flag ($1, $2, true);
		    $$ = $1;
		  }
		;

list1		: statement
		  {
		    lexer_flags.beginning_of_function = false;
		    $$ = new tree_statement_list ($1);
		  }
		| list1 sep statement
		  {
		    set_stmt_print_flag ($1, $2, true);
		    $1->append ($3);
		    $$ = $1;
		  }
		;

statement	: expression
		  {
		    octave_comment_list *comment
		      = octave_comment_buffer::get_comment ();

		    $$ = new tree_statement ($1, comment);
		  }
		| command
		  {
		    octave_comment_list *comment
		      = octave_comment_buffer::get_comment ();

		    $$ = new tree_statement ($1, comment);
		  }
		;

// ===========
// Expressions
// ===========

identifier	: NAME
		  {
		    $$ = new tree_identifier
		      ($1->sym_rec (), $1->line (), $1->column ());
		  }
		;

string		: DQ_STRING
		  { $$ = make_constant (DQ_STRING, $1); }
		| SQ_STRING
		  { $$ = make_constant (SQ_STRING, $1); }
		;

constant	: NUM
		  { $$ = make_constant (NUM, $1); }
		| IMAG_NUM
		  { $$ = make_constant (IMAG_NUM, $1); }
		| string
		  { $$ = $1; }
		;

matrix		: '[' ']'
		  {
		    $$ = new tree_constant (octave_value (Matrix ()));
		    lexer_flags.looking_at_matrix_or_assign_lhs = false;
		  }
		| '[' ';' ']'
		  {
		    $$ = new tree_constant (octave_value (Matrix ()));
		    lexer_flags.looking_at_matrix_or_assign_lhs = false;
		  }
		| '[' matrix_rows ']'
		  {
		    $$ = finish_matrix ($2);
		    lexer_flags.looking_at_matrix_or_assign_lhs = false;
		  }
		;

matrix_rows	: matrix_rows1
		  { $$ = $1; }
		| matrix_rows1 ';'	// Ignore trailing semicolon.
		  { $$ = $1; }
		;

matrix_rows1	: cell_or_matrix_row
		  { $$ = new tree_matrix ($1); }
		| matrix_rows1 ';' cell_or_matrix_row
		  {
		    $1->append ($3);
		    $$ = $1;
		  }
		;

cell		: '{' '}'
		  { $$ = new tree_constant (octave_value (Cell ())); }
		| '{' ';' '}'
		  { $$ = new tree_constant (octave_value (Cell ())); }
		| '{' cell_rows '}'
		  { $$ = finish_cell ($2); }
		;

cell_rows	: cell_rows1
		  { $$ = $1; }
		| cell_rows1 ';'	// Ignore trailing semicolon.
		  { $$ = $1; }
		;

cell_rows1	: cell_or_matrix_row
		  { $$ = new tree_cell ($1); }
		| cell_rows1 ';' cell_or_matrix_row
		  {
		    $1->append ($3);
		    $$ = $1;
		  }
		;

cell_or_matrix_row
		: arg_list
		  { $$ = $1; }
		| arg_list ','	// Ignore trailing comma.
		  { $$ = $1; }
		;

fcn_handle	: '@' FCN_HANDLE
		  {
		    $$ = make_fcn_handle ($2);
		    lexer_flags.looking_at_function_handle--;
		  }
		;

anon_fcn_handle	: '@' param_list statement
		  { $$ = make_anon_fcn_handle ($2, $3); }
		;

primary_expr	: identifier
		  { $$ = $1; }
		| constant
		  { $$ = $1; }
		| fcn_handle
		  { $$ = $1; }
		| matrix
		  { $$ = $1; }
		| cell
		  { $$ = $1; }
		| '(' expression ')'
		  { $$ = $2->mark_in_parens (); }
		;

magic_colon	: ':'
		  {
		    octave_value tmp (octave_value::magic_colon_t);
		    $$ = new tree_constant (tmp);
		  }
		;

arg_list	: expression
		  { $$ = new tree_argument_list ($1); }
		| magic_colon
		  { $$ = new tree_argument_list ($1); }
		| arg_list ',' magic_colon
		  {
		    $1->append ($3);
		    $$ = $1;
		  }
		| arg_list ',' expression
		  {
		    $1->append ($3);
		    $$ = $1;
		  }
		;

indirect_ref_op	: '.'
		  { lexer_flags.looking_at_indirect_ref = true; }
		;

// Two more rules for lexical feedback.  To avoid reduce/reduce
// conflicts, We use begin_obj_idx after every postfix_expr on the RHS
// of a rule, then cancel that as soon as possible for cases when we
// are not actually parsing an index expression.  Since all of those
// cases are simple tokens that don't involve examining the value of 
// lexer_flags.looking_at_object_index, I think we should be OK.

begin_obj_idx	: // empty
		  { lexer_flags.looking_at_object_index++; }
		;

cancel_obj_idx	: // empty
		  { lexer_flags.looking_at_object_index--; }
		;

postfix_expr	: primary_expr
		  { $$ = $1; }
		| postfix_expr begin_obj_idx '(' ')'
		  {
		    $$ = make_index_expression ($1, 0, '(');
		    lexer_flags.looking_at_object_index--;
		  }
		| postfix_expr begin_obj_idx '(' arg_list ')'
		  {
		    $$ = make_index_expression ($1, $4, '(');
		    lexer_flags.looking_at_object_index--;
		  }
		| postfix_expr begin_obj_idx '{' '}'
		  {
		    $$ = make_index_expression ($1, 0, '{');
		    lexer_flags.looking_at_object_index--;
		  }
		| postfix_expr begin_obj_idx '{' arg_list '}'
		  {
		    $$ = make_index_expression ($1, $4, '{');
		    lexer_flags.looking_at_object_index--;
		  }
		| postfix_expr begin_obj_idx PLUS_PLUS cancel_obj_idx
		  { $$ = make_postfix_op (PLUS_PLUS, $1, $3); }
		| postfix_expr begin_obj_idx MINUS_MINUS cancel_obj_idx
		  { $$ = make_postfix_op (MINUS_MINUS, $1, $3); }
		| postfix_expr begin_obj_idx QUOTE cancel_obj_idx
		  { $$ = make_postfix_op (QUOTE, $1, $3); }
		| postfix_expr begin_obj_idx TRANSPOSE cancel_obj_idx
		  { $$ = make_postfix_op (TRANSPOSE, $1, $3); }
		| postfix_expr begin_obj_idx indirect_ref_op cancel_obj_idx STRUCT_ELT
		  { $$ = make_indirect_ref ($1, $5->text ()); }
		| postfix_expr begin_obj_idx indirect_ref_op cancel_obj_idx '(' expression ')'
		  { $$ = make_indirect_ref ($1, $6); }
		;

prefix_expr	: postfix_expr begin_obj_idx cancel_obj_idx
		  { $$ = $1; }
		| binary_expr
		  { $$ = $1; }
		| PLUS_PLUS prefix_expr %prec UNARY
		  { $$ = make_prefix_op (PLUS_PLUS, $2, $1); }
		| MINUS_MINUS prefix_expr %prec UNARY
		  { $$ = make_prefix_op (MINUS_MINUS, $2, $1); }
		| EXPR_NOT prefix_expr %prec UNARY
		  { $$ = make_prefix_op (EXPR_NOT, $2, $1); }
		| '+' prefix_expr %prec UNARY
		  { $$ = make_prefix_op ('+', $2, $1); }
		| '-' prefix_expr %prec UNARY
		  { $$ = make_prefix_op ('-', $2, $1); }
		;

binary_expr	: prefix_expr POW prefix_expr
		  { $$ = make_binary_op (POW, $1, $2, $3); }
		| prefix_expr EPOW prefix_expr
		  { $$ = make_binary_op (EPOW, $1, $2, $3); }
		| prefix_expr '+' prefix_expr
		  { $$ = make_binary_op ('+', $1, $2, $3); }
		| prefix_expr '-' prefix_expr
		  { $$ = make_binary_op ('-', $1, $2, $3); }
		| prefix_expr '*' prefix_expr
		  { $$ = make_binary_op ('*', $1, $2, $3); }
		| prefix_expr '/' prefix_expr
		  { $$ = make_binary_op ('/', $1, $2, $3); }
		| prefix_expr EPLUS prefix_expr
		  { $$ = make_binary_op ('+', $1, $2, $3); }
		| prefix_expr EMINUS prefix_expr
		  { $$ = make_binary_op ('-', $1, $2, $3); }
		| prefix_expr EMUL prefix_expr
		  { $$ = make_binary_op (EMUL, $1, $2, $3); }
		| prefix_expr EDIV prefix_expr
		  { $$ = make_binary_op (EDIV, $1, $2, $3); }
		| prefix_expr LEFTDIV prefix_expr
		  { $$ = make_binary_op (LEFTDIV, $1, $2, $3); }
		| prefix_expr ELEFTDIV prefix_expr
		  { $$ = make_binary_op (ELEFTDIV, $1, $2, $3); }
		;

colon_expr	: colon_expr1
		  { $$ = finish_colon_expression ($1); }
		;

colon_expr1	: prefix_expr
		  { $$ = new tree_colon_expression ($1); }
		| colon_expr1 ':' prefix_expr
		  {
		    if (! ($$ = $1->append ($3)))
		      ABORT_PARSE;
		  }
		;

simple_expr	: colon_expr
		  { $$ = $1; }
		| simple_expr LSHIFT simple_expr
		  { $$ = make_binary_op (LSHIFT, $1, $2, $3); }
		| simple_expr RSHIFT simple_expr
		  { $$ = make_binary_op (RSHIFT, $1, $2, $3); }
		| simple_expr EXPR_LT simple_expr
		  { $$ = make_binary_op (EXPR_LT, $1, $2, $3); }
		| simple_expr EXPR_LE simple_expr
		  { $$ = make_binary_op (EXPR_LE, $1, $2, $3); }
		| simple_expr EXPR_EQ simple_expr
		  { $$ = make_binary_op (EXPR_EQ, $1, $2, $3); }
		| simple_expr EXPR_GE simple_expr
		  { $$ = make_binary_op (EXPR_GE, $1, $2, $3); }
		| simple_expr EXPR_GT simple_expr
		  { $$ = make_binary_op (EXPR_GT, $1, $2, $3); }
		| simple_expr EXPR_NE simple_expr
		  { $$ = make_binary_op (EXPR_NE, $1, $2, $3); }
		| simple_expr EXPR_AND simple_expr
		  { $$ = make_binary_op (EXPR_AND, $1, $2, $3); }
		| simple_expr EXPR_OR simple_expr
		  { $$ = make_binary_op (EXPR_OR, $1, $2, $3); }
		| simple_expr EXPR_AND_AND simple_expr
		  { $$ = make_boolean_op (EXPR_AND_AND, $1, $2, $3); }
		| simple_expr EXPR_OR_OR simple_expr
		  { $$ = make_boolean_op (EXPR_OR_OR, $1, $2, $3); }
		;

// Arrange for the lexer to return CLOSE_BRACE for `]' by looking ahead
// one token for an assignment op.

assign_lhs	: simple_expr
		  {
		    $$ = new tree_argument_list ($1);
		    $$->mark_as_simple_assign_lhs ();
		  }
		| '[' arg_list CLOSE_BRACE
		  {
		    $$ = $2;
		    lexer_flags.looking_at_matrix_or_assign_lhs = false;
		  }
		;

assign_expr	: assign_lhs '=' expression
		  { $$ = make_assign_op ('=', $1, $2, $3); }
		| assign_lhs ADD_EQ expression
		  { $$ = make_assign_op (ADD_EQ, $1, $2, $3); }
		| assign_lhs SUB_EQ expression
		  { $$ = make_assign_op (SUB_EQ, $1, $2, $3); }
		| assign_lhs MUL_EQ expression
		  { $$ = make_assign_op (MUL_EQ, $1, $2, $3); }
		| assign_lhs DIV_EQ expression
		  { $$ = make_assign_op (DIV_EQ, $1, $2, $3); }
		| assign_lhs LEFTDIV_EQ expression
		  { $$ = make_assign_op (LEFTDIV_EQ, $1, $2, $3); }
		| assign_lhs POW_EQ expression
		  { $$ = make_assign_op (POW_EQ, $1, $2, $3); }
		| assign_lhs LSHIFT_EQ expression
		  { $$ = make_assign_op (LSHIFT_EQ, $1, $2, $3); }
		| assign_lhs RSHIFT_EQ expression
		  { $$ = make_assign_op (RSHIFT_EQ, $1, $2, $3); }
		| assign_lhs EMUL_EQ expression
		  { $$ = make_assign_op (EMUL_EQ, $1, $2, $3); }
		| assign_lhs EDIV_EQ expression
		  { $$ = make_assign_op (EDIV_EQ, $1, $2, $3); }
		| assign_lhs ELEFTDIV_EQ expression
		  { $$ = make_assign_op (ELEFTDIV_EQ, $1, $2, $3); }
		| assign_lhs EPOW_EQ expression
		  { $$ = make_assign_op (EPOW_EQ, $1, $2, $3); }
		| assign_lhs AND_EQ expression
		  { $$ = make_assign_op (AND_EQ, $1, $2, $3); }
		| assign_lhs OR_EQ expression
		  { $$ = make_assign_op (OR_EQ, $1, $2, $3); }
		;

word_list_cmd	: identifier word_list
		  { $$ = make_index_expression ($1, $2, '('); }
		;

word_list	: string
		  { $$ = new tree_argument_list ($1); }
		| word_list string
		  {
		    $1->append ($2);
		    $$ = $1;
		  }
		;

expression	: simple_expr
		  { $$ = $1; }
		| word_list_cmd
		  { $$ = $1; }
		| assign_expr
		  { $$ = $1; }
		| anon_fcn_handle
		  { $$ = $1; }
		;

// ================================================
// Commands, declarations, and function definitions
// ================================================

command		: declaration
		  { $$ = $1; }
		| select_command
		  { $$ = $1; }
		| loop_command
		  { $$ = $1; }
		| jump_command
		  { $$ = $1; }
		| except_command
		  { $$ = $1; }
		| function
		  { $$ = $1; }
		;

// =====================
// Declaration statemnts
// =====================

declaration	: GLOBAL decl1
		  { $$ = make_decl_command (GLOBAL, $1, $2); }
		| STATIC decl1
		  { $$ = make_decl_command (STATIC, $1, $2); }
		;

decl1		: decl2
		  { $$ = new tree_decl_init_list ($1); }
		| decl1 decl2
		  {
		    $1->append ($2);
		    $$ = $1;
		  }
		;

decl2		: identifier
		  { $$ = new tree_decl_elt ($1); }
		| identifier '=' expression
		  { $$ = new tree_decl_elt ($1, $3); }
		;

// ====================
// Selection statements
// ====================

select_command	: if_command
		  { $$ = $1; }
		| switch_command
		  { $$ = $1; }
		;

// ============
// If statement
// ============

if_command	: IF stash_comment if_cmd_list END
		  {
		    if (! ($$ = finish_if_command ($1, $3, $4, $2)))
		      ABORT_PARSE;
		  }
		;

if_cmd_list	: if_cmd_list1
		  { $$ = $1; }
		| if_cmd_list1 else_clause
		  {
		    $1->append ($2);
		    $$ = $1;
		  }
		;

if_cmd_list1	: expression opt_sep opt_list
		  { $$ = start_if_command ($1, $3); }
		| if_cmd_list1 elseif_clause
		  {
		    $1->append ($2);
		    $$ = $1;
		  }
		;

elseif_clause	: ELSEIF stash_comment opt_sep expression opt_sep opt_list
		  { $$ = make_elseif_clause ($4, $6, $2); }
		;

else_clause	: ELSE stash_comment opt_sep opt_list
		  {
		    $$ = new tree_if_clause ($4, $2);
		  }
		;

// ================
// Switch statement
// ================

switch_command	: SWITCH stash_comment expression opt_sep case_list END
		  {
		    if (! ($$ = finish_switch_command ($1, $3, $5, $6, $2)))
		      ABORT_PARSE;
		  }
		;

case_list	: // empty
		  { $$ = new tree_switch_case_list (); }
		| case_list1
		  { $$ = $1; }
		| case_list1 default_case
		  {
		    $1->append ($2);
		    $$ = $1;
		  }		
		;

case_list1	: switch_case
		  { $$ = new tree_switch_case_list ($1); }
		| case_list1 switch_case
		  {
		    $1->append ($2);
		    $$ = $1;
		  }
		;

switch_case	: CASE stash_comment opt_sep expression opt_sep opt_list
		  { $$ = make_switch_case ($4, $6, $2); }
		;

default_case	: OTHERWISE stash_comment opt_sep opt_list
		  {
		    $$ = new tree_switch_case ($4, $2);
		  }
		;

// =======
// Looping
// =======

loop_command	: WHILE stash_comment expression opt_sep opt_list END
		  {
		    if (! ($$ = make_while_command ($1, $3, $5, $6, $2)))
		      ABORT_PARSE;
		  }
		| DO stash_comment opt_sep opt_list UNTIL expression
		  {
		    if (! ($$ = make_do_until_command ($1, $4, $6, $2)))
		      ABORT_PARSE;
		  }
		| FOR stash_comment assign_lhs '=' expression opt_sep opt_list END
		  {
		    if (! ($$ = make_for_command ($1, $3, $5, $7, $8, $2)))
		      ABORT_PARSE;
		  }
		| FOR stash_comment '(' assign_lhs '=' expression ')' opt_sep opt_list END
		  {
		    if (! ($$ = make_for_command ($1, $4, $6, $9, $10, $2)))
		      ABORT_PARSE;
		  }
		;

// =======
// Jumping
// =======

jump_command	: BREAK
		  {
		    if (! ($$ = make_break_command ($1)))
		      ABORT_PARSE;
		  }
		| CONTINUE
		  {
		    if (! ($$ = make_continue_command ($1)))
		      ABORT_PARSE;
		  }
		| FUNC_RET
		  {
		    if (! ($$ = make_return_command ($1)))
		      ABORT_PARSE;
		  }
		;

// ==========
// Exceptions
// ==========

except_command	: UNWIND stash_comment opt_sep opt_list CLEANUP
		  stash_comment opt_sep opt_list END
		  {
		    if (! ($$ = make_unwind_command ($1, $4, $8, $9, $2, $6)))
		      ABORT_PARSE;
		  }
		| TRY stash_comment opt_sep opt_list CATCH
		  stash_comment opt_sep opt_list END
		  {
		    if (! ($$ = make_try_command ($1, $4, $8, $9, $2, $6)))
		      ABORT_PARSE;
		  }
		| TRY stash_comment opt_sep opt_list END
		  {
		    if (! ($$ = make_try_command ($1, $4, 0, $5, $2, 0)))
		      ABORT_PARSE;
		  }
		;

// ===========================================
// Some `subroutines' for function definitions
// ===========================================

save_symtab	: // empty
		  { symtab_context.push (curr_sym_tab); }
		;
		   
function_symtab	: // empty
		  { curr_sym_tab = fbi_sym_tab; }
		;

local_symtab	: // empty
		  { curr_sym_tab = tmp_local_sym_tab; }
		;

// ===========================
// List of function parameters
// ===========================

param_list_beg	: '('
		  {
		    lexer_flags.looking_at_parameter_list = true;

		    if (lexer_flags.looking_at_function_handle)
		      {
		        symtab_context.push (curr_sym_tab);

			tmp_local_sym_tab = new symbol_table ();

			curr_sym_tab = tmp_local_sym_tab;

			lexer_flags.looking_at_function_handle--;
		      }
		  }
		;

param_list_end	: ')'
		  { lexer_flags.looking_at_parameter_list = false; }
		;

param_list	: param_list_beg param_list1 param_list_end
		  {
		    lexer_flags.quote_is_transpose = false;
		    $$ = $2;
		  }
		| param_list_beg error
		  {
		    yyerror ("invalid parameter list");
		    $$ = 0;
		    ABORT_PARSE;
		  }
		;

param_list1	: // empty
		  { $$ = 0; }
		| param_list2
		  {
		    $1->mark_as_formal_parameters ();
		    $$ = $1;
		  }
		| VARARGIN
		  {
		    tree_parameter_list *tmp = new tree_parameter_list ();
		    tmp->mark_varargs_only ();
		    $$ = tmp;
		  }
		| param_list2 ',' VARARGIN
		  {
		    $1->mark_as_formal_parameters ();
		    $1->mark_varargs ();
		    $$ = $1;
		  }
		;

param_list2	: decl2
		  { $$ = new tree_parameter_list ($1); }
		| param_list2 ',' decl2
		  {
		    $1->append ($3);
		    $$ = $1;
		  }
		;

// ===================================
// List of function return value names
// ===================================

return_list_beg	: '[' local_symtab
		;

return_list	: return_list_beg return_list_end
		  {
		    lexer_flags.looking_at_return_list = false;
		    $$ = new tree_parameter_list ();
		  }
		| return_list_beg VARARGOUT return_list_end
		  {
		    lexer_flags.looking_at_return_list = false;
		    tree_parameter_list *tmp = new tree_parameter_list ();
		    tmp->mark_varargs_only ();
		    $$ = tmp;
		  }
		| VARARGOUT
		  {
		    lexer_flags.looking_at_return_list = false;
		    tree_parameter_list *tmp = new tree_parameter_list ();
		    tmp->mark_varargs_only ();
		    $$ = tmp;
		  }
		| return_list_beg return_list1 return_list_end
		  {
		    lexer_flags.looking_at_return_list = false;
		    $$ = $2;
		  }
		| return_list_beg return_list1 ',' VARARGOUT return_list_end
		  {
		    lexer_flags.looking_at_return_list = false;
		    $2->mark_varargs ();
		    $$ = $2;
		  }
		;

return_list1	: identifier
		  { $$ = new tree_parameter_list (new tree_decl_elt ($1)); }
		| return_list1 ',' identifier
		  {
		    $1->append (new tree_decl_elt ($3));
		    $$ = $1;
		  }
		;

return_list_end	: function_symtab ']'
		;

// ===================
// Function definition
// ===================

function_beg	: save_symtab FCN function_symtab stash_comment
		  { $$ = $4; }
		;

function	: function_beg function2
		  {
		    $2->stash_leading_comment ($1);
		    recover_from_parsing_function ();
		    $$ = 0;
		  }
		| function_beg identifier function1
		  {
		    finish_function ($2, $3, $1);
		    recover_from_parsing_function ();
		    $$ = 0;
		  }
		| function_beg return_list function1
		  {
		    finish_function ($2, $3, $1);
		    recover_from_parsing_function ();
		    $$ = 0;
		  }
		;

function1	: function_symtab '=' function2
		  { $$ = $3; }
		;

fcn_name	: identifier local_symtab
		  {
		    std::string id_name = $1->name ();

		    if (reading_fcn_file
		        && ! lexer_flags.parsing_nested_function)
		      parent_function_name = (curr_fcn_file_name == id_name)
			? id_name : curr_fcn_file_name;

		    lexer_flags.parsed_function_name = true;

		    $$ = $1;
		  }
		;

function2	: fcn_name function3
		  {
		    std::string fname = $1->name ();

		    delete $1;

		    if (! ($$ = frob_function (fname, $2)))
		      ABORT_PARSE;
		  }
		;

function3	: param_list function4
		  { $$ = start_function ($1, $2); }
		| function4
		  { $$ = start_function (0, $1); }
		;

function4	: opt_sep opt_list function_end
		  { $$ = $2; }
		;

function_end	: END
		  {
		    if (! end_token_ok ($1, token::function_end))
		      ABORT_PARSE;
		  }
		| END_OF_INPUT
		  {
		    if (lexer_flags.parsing_nested_function)
		      lexer_flags.parsing_nested_function = -1;

		    if (! (reading_fcn_file || reading_script_file
			   || get_input_from_eval_string))
		      YYABORT;
		  }
		;

// =============
// Miscellaneous
// =============

stash_comment	: // empty
		  { $$ = octave_comment_buffer::get_comment (); }
		;

parse_error	: LEXICAL_ERROR
		  { yyerror ("parse error"); }
		| error
		;

sep_no_nl	: ','
		  { $$ = ','; }
		| ';'
		  { $$ = ';'; }
		| sep_no_nl ','
		  { $$ = $1; }
		| sep_no_nl ';'
		  { $$ = $1; }
		;

opt_sep_no_nl	: // empty
		  { $$ = 0; }
		| sep_no_nl
		  { $$ = $1; }
		;

sep		: ','
		  { $$ = ','; }
		| ';'
		  { $$ = ';'; }
		| '\n'
		  { $$ = '\n'; }
		| sep ','
		  { $$ = $1; }
		| sep ';'
		  { $$ = $1; }
		| sep '\n'
		  { $$ = $1; }
		;

opt_sep		: // empty
		  { $$ = 0; }
		| sep
		  { $$ = $1; }
		;

%%

// Generic error messages.

static void
yyerror (const char *s)
{
  int err_col = current_input_column - 1;

  std::ostringstream output_buf;

  if (reading_fcn_file || reading_script_file)
    output_buf << "parse error near line " << input_line_number
	       << " of file " << curr_fcn_file_full_name;
  else
    output_buf << "parse error:";

  if (s && strcmp (s, "parse error") != 0)
    output_buf << "\n\n  " << s;

  output_buf << "\n\n";

  if (! current_input_line.empty ())
    {
      size_t len = current_input_line.length ();

      if (current_input_line[len-1] == '\n')
        current_input_line.resize (len-1);

      // Print the line, maybe with a pointer near the error token.

      output_buf << ">>> " << current_input_line << "\n";

      if (err_col == 0)
	err_col = len;

      for (int i = 0; i < err_col + 3; i++)
	output_buf << " ";

      output_buf << "^";
    }

  output_buf << "\n";

  std::string msg = output_buf.str ();

  parse_error ("%s", msg.c_str ());
}

// Error mesages for mismatched end tokens.

static void
end_error (const char *type, token::end_tok_type ettype, int l, int c)
{
  static const char *fmt
    = "`%s' command matched by `%s' near line %d column %d";

  switch (ettype)
    {
    case token::simple_end:
      error (fmt, type, "end", l, c);
      break;

    case token::for_end:
      error (fmt, type, "endfor", l, c);
      break;

    case token::function_end:
      error (fmt, type, "endfunction", l, c);
      break;

    case token::if_end:
      error (fmt, type, "endif", l, c);
      break;

    case token::switch_end:
      error (fmt, type, "endswitch", l, c); 
      break;

    case token::while_end:
      error (fmt, type, "endwhile", l, c); 
      break;

    case token::try_catch_end:
      error (fmt, type, "end_try_catch", l, c); 
      break;

    case token::unwind_protect_end:
      error (fmt, type, "end_unwind_protect", l, c); 
      break;

    default:
      panic_impossible ();
      break;
    }
}

// Check to see that end tokens are properly matched.

static bool
end_token_ok (token *tok, token::end_tok_type expected)
{
  bool retval = true;

  token::end_tok_type ettype = tok->ettype ();

  if (ettype != expected && ettype != token::simple_end)
    {
      retval = false;

      yyerror ("parse error");

      int l = tok->line ();
      int c = tok->column ();

      switch (expected)
	{
	case token::for_end:
	  end_error ("for", ettype, l, c);
	  break;

	case token::function_end:
	  end_error ("function", ettype, l, c);
	  break;

	case token::if_end:
	  end_error ("if", ettype, l, c);
	  break;

	case token::try_catch_end:
	  end_error ("try", ettype, l, c);
	  break;

	case token::switch_end:
	  end_error ("switch", ettype, l, c);
	  break;

	case token::unwind_protect_end:
	  end_error ("unwind_protect", ettype, l, c);
	  break;

	case token::while_end:
	  end_error ("while", ettype, l, c);
	  break;

	default:
	  panic_impossible ();
	  break;
	}
    }

  return retval;
}

// Maybe print a warning if an assignment expression is used as the
// test in a logical expression.

static void
maybe_warn_assign_as_truth_value (tree_expression *expr)
{
  if (expr->is_assignment_expression ()
      && expr->paren_count () < 2)
    {
      warning_with_id
        ("Octave:assign-as-truth-value",
         "suggest parenthesis around assignment used as truth value");
    }
}

// Maybe print a warning about switch labels that aren't constants.

static void
maybe_warn_variable_switch_label (tree_expression *expr)
{
  if (! expr->is_constant ())
    warning_with_id ("Octave:variable-switch-label",
    		     "variable switch label");
}

static tree_expression *
fold (tree_binary_expression *e)
{
  tree_expression *retval = e;

  unwind_protect::begin_frame ("fold_binary_expression");

  unwind_protect_int (error_state);
  unwind_protect_int (warning_state);

  unwind_protect_bool (discard_error_messages);
  unwind_protect_bool (discard_warning_messages);

  discard_error_messages = true;
  discard_warning_messages = true;

  tree_expression *op1 = e->lhs ();
  tree_expression *op2 = e->rhs ();

  octave_value::binary_op op_type = e->op_type ();

  if (op1->is_constant () && op2->is_constant ()
      && (! ((warning_enabled ("Octave:associativity-change")
	      && (op_type == POW || op_type == EPOW))
	     || (warning_enabled ("Octave:precedence-change")
		 && (op_type == EXPR_OR || op_type == EXPR_OR_OR)))))
    {
      octave_value tmp = e->rvalue ();

      if (! (error_state || warning_state))
	{
	  tree_constant *tc_retval = new tree_constant (tmp);

	  std::ostringstream buf;

	  tree_print_code tpc (buf);

	  e->accept (tpc);

	  tc_retval->stash_original_text (buf.str ());

	  delete e;

	  retval = tc_retval;
	}
    }

  unwind_protect::run_frame ("fold_binary_expression");

  return retval;
}

static tree_expression *
fold (tree_unary_expression *e)
{
  tree_expression *retval = e;

  unwind_protect::begin_frame ("fold_unary_expression");

  unwind_protect_int (error_state);
  unwind_protect_int (warning_state);

  unwind_protect_bool (discard_error_messages);
  unwind_protect_bool (discard_warning_messages);

  discard_error_messages = true;
  discard_warning_messages = true;

  tree_expression *op = e->operand ();

  if (op->is_constant ())
    {
      octave_value tmp = e->rvalue ();

      if (! (error_state || warning_state))
	{
	  tree_constant *tc_retval = new tree_constant (tmp);

	  std::ostringstream buf;

	  tree_print_code tpc (buf);

	  e->accept (tpc);

	  tc_retval->stash_original_text (buf.str ());

	  delete e;

	  retval = tc_retval;
	}
    }

  unwind_protect::run_frame ("fold_unary_expression");

  return retval;
}

// Finish building a range.

static tree_expression *
finish_colon_expression (tree_colon_expression *e)
{
  tree_expression *retval = e;

  unwind_protect::begin_frame ("finish_colon_expression");

  unwind_protect_int (error_state);
  unwind_protect_int (warning_state);

  unwind_protect_bool (discard_error_messages);
  unwind_protect_bool (discard_warning_messages);

  discard_error_messages = true;
  discard_warning_messages = true;

  tree_expression *base = e->base ();
  tree_expression *limit = e->limit ();
  tree_expression *incr = e->increment ();

  if (base)
    {
      if (limit)
	{
	  if (base->is_constant () && limit->is_constant ()
	      && (! incr || (incr && incr->is_constant ())))
	    {
	      octave_value tmp = e->rvalue ();

	      if (! (error_state || warning_state))
		{
		  tree_constant *tc_retval = new tree_constant (tmp);

		  std::ostringstream buf;

		  tree_print_code tpc (buf);

		  e->accept (tpc);

		  tc_retval->stash_original_text (buf.str ());

		  delete e;

		  retval = tc_retval;
		}
	    }
	}
      else
	{
	  e->preserve_base ();
	  delete e;

	  // FIXME -- need to attempt constant folding here
	  // too (we need a generic way to do that).
	  retval = base;
	}
    }

  unwind_protect::run_frame ("finish_colon_expression");

  return retval;
}

// Make a constant.

static tree_constant *
make_constant (int op, token *tok_val)
{
  int l = tok_val->line ();
  int c = tok_val->column ();

  tree_constant *retval = 0;

  switch (op)
    {
    case NUM:
      {
	octave_value tmp (tok_val->number ());
	retval = new tree_constant (tmp, l, c);
	retval->stash_original_text (tok_val->text_rep ());
      }
      break;

    case IMAG_NUM:
      {
	octave_value tmp (Complex (0.0, tok_val->number ()));
	retval = new tree_constant (tmp, l, c);
	retval->stash_original_text (tok_val->text_rep ());
      }
      break;

    case DQ_STRING:
    case SQ_STRING:
      {
	octave_value tmp (tok_val->text (), op == DQ_STRING ? '"' : '\'');
	retval = new tree_constant (tmp, l, c);
      }
      break;

    default:
      panic_impossible ();
      break;
    }

  return retval;
}

// Make a function handle.

static tree_fcn_handle *
make_fcn_handle (token *tok_val)
{
  int l = tok_val->line ();
  int c = tok_val->column ();

  tree_fcn_handle *retval = new tree_fcn_handle (tok_val->text (), l, c);

  return retval;
}

// Make an anonymous function handle.

static tree_anon_fcn_handle *
make_anon_fcn_handle (tree_parameter_list *param_list, tree_statement *stmt)
{
  // FIXME -- need to get these from the location of the @ symbol.

  int l = -1;
  int c = -1;

  tree_parameter_list *ret_list = 0;

  symbol_table *fcn_sym_tab = curr_sym_tab;

  if (symtab_context.empty ())
    panic_impossible ();

  curr_sym_tab = symtab_context.top ();

  symtab_context.pop ();

  if (stmt && stmt->is_expression ())
    stmt->set_print_flag (false);

  tree_statement_list *body = new tree_statement_list (stmt);

  body->mark_as_function_body ();

  tree_anon_fcn_handle *retval
    = new tree_anon_fcn_handle (param_list, ret_list, body, fcn_sym_tab, l, c);

  return retval;
}

static void
maybe_warn_associativity_change (tree_expression *op)
{
  if (op->paren_count () == 0 && op->is_binary_expression ())
    {
      tree_binary_expression *e
	= dynamic_cast<tree_binary_expression *> (op);

      octave_value::binary_op op_type = e->op_type ();

      if (op_type == octave_value::op_pow
	  || op_type == octave_value::op_el_pow)
	{
	  std::string op_str = octave_value::binary_op_as_string (op_type);

	  warning_with_id
	    ("Octave:associativity-change",
	     "meaning may have changed due to change in associativity for %s operator", op_str.c_str ());
        }
    }
}

// Build a binary expression.

static tree_expression *
make_binary_op (int op, tree_expression *op1, token *tok_val,
		tree_expression *op2)
{
  octave_value::binary_op t = octave_value::unknown_binary_op;

  switch (op)
    {
    case POW:
      t = octave_value::op_pow;
      maybe_warn_associativity_change (op1);
      break;

    case EPOW:
      t = octave_value::op_el_pow;
      maybe_warn_associativity_change (op1);
      break;

    case '+':
      t = octave_value::op_add;
      break;

    case '-':
      t = octave_value::op_sub;
      break;

    case '*':
      t = octave_value::op_mul;
      break;

    case '/':
      t = octave_value::op_div;
      break;

    case EMUL:
      t = octave_value::op_el_mul;
      break;

    case EDIV:
      t = octave_value::op_el_div;
      break;

    case LEFTDIV:
      t = octave_value::op_ldiv;
      break;

    case ELEFTDIV:
      t = octave_value::op_el_ldiv;
      break;

    case LSHIFT:
      t = octave_value::op_lshift;
      break;

    case RSHIFT:
      t = octave_value::op_rshift;
      break;

    case EXPR_LT:
      t = octave_value::op_lt;
      break;

    case EXPR_LE:
      t = octave_value::op_le;
      break;

    case EXPR_EQ:
      t = octave_value::op_eq;
      break;

    case EXPR_GE:
      t = octave_value::op_ge;
      break;

    case EXPR_GT:
      t = octave_value::op_gt;
      break;

    case EXPR_NE:
      t = octave_value::op_ne;
      break;

    case EXPR_AND:
      t = octave_value::op_el_and;
      break;

    case EXPR_OR:
      t = octave_value::op_el_or;
      if (op2->paren_count () == 0 && op2->is_binary_expression ())
        {
	  tree_binary_expression *e
	    = dynamic_cast<tree_binary_expression *> (op2);

	  if (e->op_type () == octave_value::op_el_and)
	    warning_with_id
	      ("Octave:precedence-change",
	       "meaning may have changed due to change in precedence for & and | operators");
        }
      break;

    default:
      panic_impossible ();
      break;
    }

  int l = tok_val->line ();
  int c = tok_val->column ();

  tree_binary_expression *e
    = new tree_binary_expression (op1, op2, l, c, t);

  return fold (e);
}

// Build a boolean expression.

static tree_expression *
make_boolean_op (int op, tree_expression *op1, token *tok_val,
		 tree_expression *op2)
{
  tree_boolean_expression::type t;

  switch (op)
    {
    case EXPR_AND_AND:
      t = tree_boolean_expression::bool_and;
      break;

    case EXPR_OR_OR:
      t = tree_boolean_expression::bool_or;
      if (op2->paren_count () == 0 && op2->is_boolean_expression ())
        {
	  tree_boolean_expression *e
	    = dynamic_cast<tree_boolean_expression *> (op2);

	  if (e->op_type () == tree_boolean_expression::bool_and)
	    warning_with_id
	      ("Octave:precedence-change",
	       "meaning may have changed due to change in precedence for && and || operators");
        }
      break;

    default:
      panic_impossible ();
      break;
    }

  int l = tok_val->line ();
  int c = tok_val->column ();

  tree_boolean_expression *e
    = new tree_boolean_expression (op1, op2, l, c, t);

  return fold (e);
}

// Build a prefix expression.

static tree_expression *
make_prefix_op (int op, tree_expression *op1, token *tok_val)
{
  octave_value::unary_op t = octave_value::unknown_unary_op;

  switch (op)
    {
    case EXPR_NOT:
      t = octave_value::op_not;
      break;

    case '+':
      t = octave_value::op_uplus;
      break;

    case '-':
      t = octave_value::op_uminus;
      break;

    case PLUS_PLUS:
      t = octave_value::op_incr;
      break;

    case MINUS_MINUS:
      t = octave_value::op_decr;
      break;

    default:
      panic_impossible ();
      break;
    }

  int l = tok_val->line ();
  int c = tok_val->column ();

  tree_prefix_expression *e
    = new tree_prefix_expression (op1, l, c, t);

  return fold (e);
}

// Build a postfix expression.

static tree_expression *
make_postfix_op (int op, tree_expression *op1, token *tok_val)
{
  octave_value::unary_op t = octave_value::unknown_unary_op;

  switch (op)
    {
    case QUOTE:
      t = octave_value::op_hermitian;
      break;

    case TRANSPOSE:
      t = octave_value::op_transpose;
      break;

    case PLUS_PLUS:
      t = octave_value::op_incr;
      break;

    case MINUS_MINUS:
      t = octave_value::op_decr;
      break;

    default:
      panic_impossible ();
      break;
    }

  int l = tok_val->line ();
  int c = tok_val->column ();

  tree_postfix_expression *e
    = new tree_postfix_expression (op1, l, c, t);

  return fold (e);
}

// Build an unwind-protect command.

static tree_command *
make_unwind_command (token *unwind_tok, tree_statement_list *body,
		     tree_statement_list *cleanup, token *end_tok,
		     octave_comment_list *lc, octave_comment_list *mc)
{
  tree_command *retval = 0;

  if (end_token_ok (end_tok, token::unwind_protect_end))
    {
      octave_comment_list *tc = octave_comment_buffer::get_comment ();

      int l = unwind_tok->line ();
      int c = unwind_tok->column ();

      retval = new tree_unwind_protect_command (body, cleanup,
						lc, mc, tc, l, c);
    }

  return retval;
}

// Build a try-catch command.

static tree_command *
make_try_command (token *try_tok, tree_statement_list *body,
		  tree_statement_list *cleanup, token *end_tok,
		  octave_comment_list *lc, octave_comment_list *mc)
{
  tree_command *retval = 0;

  if (end_token_ok (end_tok, token::try_catch_end))
    {
      octave_comment_list *tc = octave_comment_buffer::get_comment ();

      int l = try_tok->line ();
      int c = try_tok->column ();

      retval = new tree_try_catch_command (body, cleanup,
					   lc, mc, tc, l, c);
    }

  return retval;
}

// Build a while command.

static tree_command *
make_while_command (token *while_tok, tree_expression *expr,
		    tree_statement_list *body, token *end_tok,
		    octave_comment_list *lc)
{
  tree_command *retval = 0;

  maybe_warn_assign_as_truth_value (expr);

  if (end_token_ok (end_tok, token::while_end))
    {
      octave_comment_list *tc = octave_comment_buffer::get_comment ();

      lexer_flags.looping--;

      int l = while_tok->line ();
      int c = while_tok->column ();

      retval = new tree_while_command (expr, body, lc, tc, l, c);
    }

  return retval;
}

// Build a do-until command.

static tree_command *
make_do_until_command (token *do_tok, tree_statement_list *body,
		       tree_expression *expr, octave_comment_list *lc)
{
  tree_command *retval = 0;

  maybe_warn_assign_as_truth_value (expr);

  octave_comment_list *tc = octave_comment_buffer::get_comment ();

  lexer_flags.looping--;

  int l = do_tok->line ();
  int c = do_tok->column ();

  retval = new tree_do_until_command (expr, body, lc, tc, l, c);

  return retval;
}

// Build a for command.

static tree_command *
make_for_command (token *for_tok, tree_argument_list *lhs,
		  tree_expression *expr, tree_statement_list *body,
		  token *end_tok, octave_comment_list *lc)
{
  tree_command *retval = 0;

  if (end_token_ok (end_tok, token::for_end))
    {
      octave_comment_list *tc = octave_comment_buffer::get_comment ();

      lexer_flags.looping--;

      int l = for_tok->line ();
      int c = for_tok->column ();

      if (lhs->length () == 1)
	{
	  tree_expression *tmp = lhs->remove_front ();

	  retval = new tree_simple_for_command (tmp, expr, body,
						lc, tc, l, c);

	  delete lhs;
	}
      else
	retval = new tree_complex_for_command (lhs, expr, body,
					       lc, tc, l, c);
    }

  return retval;
}

// Build a break command.

static tree_command *
make_break_command (token *break_tok)
{
  tree_command *retval = 0;

  int l = break_tok->line ();
  int c = break_tok->column ();

  if (lexer_flags.looping || lexer_flags.defining_func
      || reading_script_file || evaluating_function_body
      || evaluating_looping_command)
    retval = new tree_break_command (l, c);
  else
    retval = new tree_no_op_command ("break", l, c);

  return retval;
}

// Build a continue command.

static tree_command *
make_continue_command (token *continue_tok)
{
  tree_command *retval = 0;

  int l = continue_tok->line ();
  int c = continue_tok->column ();

  if (lexer_flags.looping || evaluating_looping_command)
    retval = new tree_continue_command (l, c);
  else
    retval = new tree_no_op_command ("continue", l, c);

  return retval;
}

// Build a return command.

static tree_command *
make_return_command (token *return_tok)
{
  tree_command *retval = 0;

  int l = return_tok->line ();
  int c = return_tok->column ();

  if (lexer_flags.defining_func || reading_script_file
      || evaluating_function_body)
    retval = new tree_return_command (l, c);
  else
    retval = new tree_no_op_command ("return", l, c);

  return retval;
}

// Start an if command.

static tree_if_command_list *
start_if_command (tree_expression *expr, tree_statement_list *list)
{
  maybe_warn_assign_as_truth_value (expr);

  tree_if_clause *t = new tree_if_clause (expr, list);

  return new tree_if_command_list (t);
}

// Finish an if command.

static tree_if_command *
finish_if_command (token *if_tok, tree_if_command_list *list,
		   token *end_tok, octave_comment_list *lc)
{
  tree_if_command *retval = 0;

  if (end_token_ok (end_tok, token::if_end))
    {
      octave_comment_list *tc = octave_comment_buffer::get_comment ();

      int l = if_tok->line ();
      int c = if_tok->column ();

      retval = new tree_if_command (list, lc, tc, l, c);
    }

  return retval;
}

// Build an elseif clause.

static tree_if_clause *
make_elseif_clause (tree_expression *expr, tree_statement_list *list,
		    octave_comment_list *lc)
{
  maybe_warn_assign_as_truth_value (expr);

  return new tree_if_clause (expr, list, lc);
}

// Finish a switch command.

static tree_switch_command *
finish_switch_command (token *switch_tok, tree_expression *expr,
		       tree_switch_case_list *list, token *end_tok,
		       octave_comment_list *lc)
{
  tree_switch_command *retval = 0;

  if (end_token_ok (end_tok, token::switch_end))
    {
      octave_comment_list *tc = octave_comment_buffer::get_comment ();

      int l = switch_tok->line ();
      int c = switch_tok->column ();

      retval = new tree_switch_command (expr, list, lc, tc, l, c);
    }

  return retval;
}

// Build a switch case.

static tree_switch_case *
make_switch_case (tree_expression *expr, tree_statement_list *list,
		  octave_comment_list *lc)
{
  maybe_warn_variable_switch_label (expr);

  return new tree_switch_case (expr, list, lc);
}

// Build an assignment to a variable.

static tree_expression *
make_assign_op (int op, tree_argument_list *lhs, token *eq_tok,
		tree_expression *rhs)
{
  tree_expression *retval = 0;

  octave_value::assign_op t = octave_value::unknown_assign_op;

  switch (op)
    {
    case '=':
      t = octave_value::op_asn_eq;
      break;

    case ADD_EQ:
      t = octave_value::op_add_eq;
      break;

    case SUB_EQ:
      t = octave_value::op_sub_eq;
      break;

    case MUL_EQ:
      t = octave_value::op_mul_eq;
      break;

    case DIV_EQ:
      t = octave_value::op_div_eq;
      break;

    case LEFTDIV_EQ:
      t = octave_value::op_ldiv_eq;
      break;

    case POW_EQ:
      t = octave_value::op_pow_eq;
      break;

    case LSHIFT_EQ:
      t = octave_value::op_lshift_eq;
      break;

    case RSHIFT_EQ:
      t = octave_value::op_rshift_eq;
      break;

    case EMUL_EQ:
      t = octave_value::op_el_mul_eq;
      break;

    case EDIV_EQ:
      t = octave_value::op_el_div_eq;
      break;

    case ELEFTDIV_EQ:
      t = octave_value::op_el_ldiv_eq;
      break;

    case EPOW_EQ:
      t = octave_value::op_el_pow_eq;
      break;

    case AND_EQ:
      t = octave_value::op_el_and_eq;
      break;

    case OR_EQ:
      t = octave_value::op_el_or_eq;
      break;

    default:
      panic_impossible ();
      break;
    }

  int l = eq_tok->line ();
  int c = eq_tok->column ();

  if (lhs->is_simple_assign_lhs ())
    {
      tree_expression *tmp = lhs->remove_front ();

      retval = new tree_simple_assignment (tmp, rhs, false, l, c, t);

      delete lhs;
    }
  else
    return new tree_multi_assignment (lhs, rhs, false, l, c, t);

  return retval;
}

// Begin defining a function.

static octave_user_function *
start_function (tree_parameter_list *param_list, tree_statement_list *body)
{
  body->mark_as_function_body ();

  // We'll fill in the return list later.

  octave_user_function *fcn
    = new octave_user_function (param_list, 0, body, curr_sym_tab);

  if (fcn)
    {
      octave_comment_list *tc = octave_comment_buffer::get_comment ();

      fcn->stash_trailing_comment (tc);
    }

  return fcn;
}

// Do most of the work for defining a function.

static octave_user_function *
frob_function (const std::string& fname, octave_user_function *fcn)
{
  std::string id_name = fname;

  // If input is coming from a file, issue a warning if the name of
  // the file does not match the name of the function stated in the
  // file.  Matlab doesn't provide a diagnostic (it ignores the stated
  // name).

  if (reading_fcn_file || autoloading)
    {
      if (! (lexer_flags.parsing_nested_function || autoloading)
          && curr_fcn_file_name != id_name)
	{
	  warning_with_id
	    ("Octave:function-name-clash",
	     "function name `%s' does not agree with function file name `%s'",
	     id_name.c_str (), curr_fcn_file_full_name.c_str ());

	  id_name = curr_fcn_file_name;
	}

      octave_time now;

      fcn->stash_fcn_file_name (curr_fcn_file_full_name);
      fcn->stash_fcn_file_time (now);
      fcn->mark_as_system_fcn_file ();

      if (fcn_file_from_relative_lookup)
	fcn->mark_relative ();

      if (lexer_flags.parsing_nested_function)
        fcn->stash_parent_fcn_name (parent_function_name);

      std::string nm = fcn->fcn_file_name ();

      file_stat fs (nm);

      if (fs && fs.is_newer (now))
        warning_with_id ("Octave:future-time-stamp",
			 "time stamp for `%s' is in the future", nm.c_str ());
    }
  else if (! (input_from_tmp_history_file || input_from_startup_file)
	   && reading_script_file
	   && curr_fcn_file_name == id_name)
    {
      warning ("function `%s' defined within script file `%s'",
	       id_name.c_str (), curr_fcn_file_full_name.c_str ());
    }

  fcn->stash_function_name (id_name);

  // Enter the new function in fbi_sym_tab.  If there is already a
  // variable of the same name in the current symbol table, we won't
  // find the new function when we try to call it, so we need to clear
  // the old symbol from the current symbol table.  Note that this
  // means that for things like
  //
  //   function f () eval ("function g () 1, end"); end
  //   g = 13;
  //   f ();
  //   g
  //
  // G will still refer to the variable G (with value 13) rather
  // than the function G, until the variable G is cleared.

  curr_sym_tab->clear (id_name);

  if (! lexer_flags.parsing_nested_function
      && symtab_context.top () == top_level_sym_tab)
    {
      symbol_record *sr = top_level_sym_tab->lookup (id_name);

      // Only clear the existing name if it is already defined as a
      // function.  If there is already a variable defined with the
      // same name as a the current function, it will continue to
      // shadow this name until the variable is cleared.  This means
      // that for something like the following at the command line,
      //
      //   f = 13;
      //   function f () 7, end
      //   f
      //
      // F will still refer to the variable F (with value 13) rather
      // than the function F, until the variable F is cleared.

      if (sr && sr->is_function ())
	top_level_sym_tab->clear (id_name);
    }

  symbol_record *sr = fbi_sym_tab->lookup (id_name, true);

  if (sr)
    {
      fcn->stash_symtab_ptr (sr);

      if (lexer_flags.parsing_nested_function)
        {
          fcn->mark_as_nested_function ();
	  sr->hide ();
	}
    }
  else
    panic_impossible ();

  sr->define (fcn, symbol_record::USER_FUNCTION);

  if (! help_buf.empty ())
    {
      sr->document (help_buf.top ());
      help_buf.pop ();
    }

  // Also insert the full name in the symbol table.  This way, we can
  // properly cope with changes to LOADPATH.

  if (reading_fcn_file)
    {
      symbol_record *full_sr
        = fbi_sym_tab->lookup (curr_fcn_file_full_name, true);

      full_sr->alias (sr, true);
      full_sr->hide ();
    }

  if (lexer_flags.parsing_nested_function < 0)
    lexer_flags.parsing_nested_function = 0;

  return fcn;
}

// Finish defining a function.

static octave_user_function *
finish_function (tree_identifier *id, octave_user_function *fcn,
		 octave_comment_list *lc)
{
  tree_decl_elt *tmp = new tree_decl_elt (id);

  tree_parameter_list *tpl = new tree_parameter_list (tmp);

  tpl->mark_as_formal_parameters ();

  fcn->stash_leading_comment (lc);

  return fcn->define_ret_list (tpl);
}

// Finish defining a function a different way.

static octave_user_function *
finish_function (tree_parameter_list *ret_list,
		 octave_user_function *fcn, octave_comment_list *lc)
{
  ret_list->mark_as_formal_parameters ();

  fcn->stash_leading_comment (lc);

  return fcn->define_ret_list (ret_list);
}

static void
recover_from_parsing_function (void)
{
  if (symtab_context.empty ())
    panic_impossible ();

  curr_sym_tab = symtab_context.top ();
  symtab_context.pop ();

  lexer_flags.defining_func = false;
  lexer_flags.beginning_of_function = false;
  lexer_flags.parsed_function_name = false;
  lexer_flags.looking_at_return_list = false;
  lexer_flags.looking_at_parameter_list = false;
}

// Make an index expression.

static tree_index_expression *
make_index_expression (tree_expression *expr, tree_argument_list *args,
		       char type)
{
  tree_index_expression *retval = 0;

  int l = expr->line ();
  int c = expr->column ();

  expr->mark_postfix_indexed ();

  if (expr->is_index_expression ())
    {
      tree_index_expression *tmp = static_cast<tree_index_expression *> (expr);

      tmp->append (args, type);

      retval = tmp;
    }
  else
    retval = new tree_index_expression (expr, args, l, c, type);

  return retval;
}

// Make an indirect reference expression.

static tree_index_expression *
make_indirect_ref (tree_expression *expr, const std::string& elt)
{
  tree_index_expression *retval = 0;

  int l = expr->line ();
  int c = expr->column ();

  if (expr->is_index_expression ())
    {
      tree_index_expression *tmp = static_cast<tree_index_expression *> (expr);

      tmp->append (elt);

      retval = tmp;
    }
  else
    retval = new tree_index_expression (expr, elt, l, c);

  lexer_flags.looking_at_indirect_ref = false;

  return retval;
}

// Make an indirect reference expression with dynamic field name.

static tree_index_expression *
make_indirect_ref (tree_expression *expr, tree_expression *elt)
{
  tree_index_expression *retval = 0;

  int l = expr->line ();
  int c = expr->column ();

  if (expr->is_index_expression ())
    {
      tree_index_expression *tmp = static_cast<tree_index_expression *> (expr);

      tmp->append (elt);

      retval = tmp;
    }
  else
    retval = new tree_index_expression (expr, elt, l, c);

  lexer_flags.looking_at_indirect_ref = false;

  return retval;
}

// Make a declaration command.

static tree_decl_command *
make_decl_command (int tok, token *tok_val, tree_decl_init_list *lst)
{
  tree_decl_command *retval = 0;

  int l = tok_val->line ();
  int c = tok_val->column ();

  switch (tok)
    {
    case GLOBAL:
      retval = new tree_global_command (lst, l, c);
      break;

    case STATIC:
      if (lexer_flags.defining_func)
	retval = new tree_static_command (lst, l, c);
      else
	{
	  if (reading_script_file)
	    warning ("ignoring persistent declaration near line %d of file `%s'",
		     l, curr_fcn_file_full_name.c_str ());
	  else
	    warning ("ignoring persistent declaration near line %d", l);
	}
      break;

    default:
      panic_impossible ();
      break;
    }

  return retval;
}

// Finish building a matrix list.

static tree_expression *
finish_matrix (tree_matrix *m)
{
  tree_expression *retval = m;

  unwind_protect::begin_frame ("finish_matrix");

  unwind_protect_int (error_state);
  unwind_protect_int (warning_state);

  unwind_protect_bool (discard_error_messages);
  unwind_protect_bool (discard_warning_messages);

  discard_error_messages = true;
  discard_warning_messages = true;

  if (m->all_elements_are_constant ())
    {
      octave_value tmp = m->rvalue ();

      if (! (error_state || warning_state))
	{
	  tree_constant *tc_retval = new tree_constant (tmp);

	  std::ostringstream buf;

	  tree_print_code tpc (buf);

	  m->accept (tpc);

	  tc_retval->stash_original_text (buf.str ());

	  delete m;

	  retval = tc_retval;
	}
    }

  unwind_protect::run_frame ("finish_matrix");

  return retval;
}

// Finish building a cell list.

static tree_expression *
finish_cell (tree_cell *c)
{
  return finish_matrix (c);
}

static void
maybe_warn_missing_semi (tree_statement_list *t)
{
  if (lexer_flags.defining_func)
    {
      tree_statement *tmp = t->back();

      if (tmp->is_expression ())
	warning_with_id
	  ("Octave:missing-semicolon",
	   "missing semicolon near line %d, column %d in file `%s'",
	    tmp->line (), tmp->column (), curr_fcn_file_full_name.c_str ());
    }
}

static void
set_stmt_print_flag (tree_statement_list *list, char sep,
		     bool warn_missing_semi)
{
  switch (sep)
    {
    case ';':
      {
	tree_statement *tmp = list->back ();
	tmp->set_print_flag (0);
      }
      break;

    case 0:
    case ',':
    case '\n':
      if (warn_missing_semi)
	maybe_warn_missing_semi (list);
      break;

    default:
      warning ("unrecognized separator type!");
      break;
    }
}

void
parse_and_execute (FILE *f)
{
  unwind_protect::begin_frame ("parse_and_execute");

  unwind_protect_ptr (global_command);

  YY_BUFFER_STATE old_buf = current_buffer ();
  YY_BUFFER_STATE new_buf = create_buffer (f);

  unwind_protect::add (restore_input_buffer, old_buf);
  unwind_protect::add (delete_input_buffer, new_buf);

  switch_to_buffer (new_buf);

  unwind_protect_bool (line_editing);
  unwind_protect_bool (get_input_from_eval_string);
  unwind_protect_bool (parser_end_of_input);

  line_editing = false;
  get_input_from_eval_string = false;
  parser_end_of_input = false;

  unwind_protect_ptr (curr_sym_tab);

  int retval;
  do
    {
      reset_parser ();

      retval = yyparse ();

      if (retval == 0)
        {
          if (global_command)
	    {
	      global_command->eval ();

	      delete global_command;

	      global_command = 0;

	      OCTAVE_QUIT;

	      bool quit = (tree_return_command::returning
			   || tree_break_command::breaking);

	      if (tree_return_command::returning)
		tree_return_command::returning = 0;

	      if (tree_break_command::breaking)
		tree_break_command::breaking--;

	      if (error_state)
		{
		  error ("near line %d of file `%s'", input_line_number,
			 curr_fcn_file_full_name.c_str ());

		  break;
		}

	      if (quit)
		break;
	    }
	  else if (parser_end_of_input)
	    break;
        }
    }
  while (retval == 0);

  unwind_protect::run_frame ("parse_and_execute");
}

static void
safe_fclose (void *f)
{
  // FIXME -- comments at the end of an input file are
  // discarded (otherwise, they would be appended to the next
  // statement, possibly from the command line or another file, which
  // can be quite confusing).

  octave_comment_list *tc = octave_comment_buffer::get_comment ();

  delete tc;

  if (f)
    fclose (static_cast<FILE *> (f));
}

void
parse_and_execute (const std::string& s, bool verbose, const char *warn_for)
{
  unwind_protect::begin_frame ("parse_and_execute_2");

  unwind_protect_bool (reading_script_file);
  unwind_protect_str (curr_fcn_file_full_name);

  reading_script_file = true;
  curr_fcn_file_full_name = s;

  FILE *f = get_input_from_file (s, 0);

  if (f)
    {
      unwind_protect::add (safe_fclose, f);

      octave_user_script *script = new octave_user_script (s, s, "");
      octave_call_stack::push (script);
      unwind_protect::add (octave_call_stack::unwind_pop_script, 0);

      unwind_protect_int (input_line_number);
      unwind_protect_int (current_input_column);

      input_line_number = 0;
      current_input_column = 1;

      if (verbose)
	{
	  std::cout << "reading commands from " << s << " ... ";
	  reading_startup_message_printed = true;
	  std::cout.flush ();
	}

      parse_and_execute (f);

      if (verbose)
	std::cout << "done." << std::endl;
    }
  else if (warn_for)
    error ("%s: unable to open file `%s'", warn_for, s.c_str ());

  unwind_protect::run_frame ("parse_and_execute_2");
}

static bool
looks_like_copyright (const std::string& s)
{
  // Perhaps someday we will want to do more here, so leave this as a
  // separate function.

  return (s.substr (0, 9) == "Copyright");
}

static int
text_getc (FILE *f)
{
  int c = getc (f);

  // Convert CRLF into just LF.

  if (c == '\r')
    {
      c = getc (f);

      if (c != '\n')
	{
	  ungetc (c, f);
	  c = '\r';
	}
    }

  return c;
}

// Eat whitespace and comments from FFILE, returning the text of the
// comments read if it doesn't look like a copyright notice.  If
// IN_PARTS, consider each block of comments separately; otherwise,
// grab them all at once.  If UPDATE_POS is TRUE, line and column
// number information is updated.  If SAVE_COPYRIGHT is TRUE, then
// comments that are recognized as a copyright notice are saved in the
// comment buffer.  If SKIP_CODE is TRUE, then ignore code, otherwise
// stop at the first non-whitespace character that is not part of a
// comment.

// FIXME -- skipping code will fail for something like this:
//
//   function foo (x)
//     fprintf ('%d\n', x);
//
//   % This is the help for foo.
//
// because we recognize the '%' in the fprintf format as a comment
// character.  Fixing this will probably require actually parsing the
// file properly.

// FIXME -- grab_help_text() in lex.l duplicates some of this
// code!

static std::string
gobble_leading_white_space (FILE *ffile, bool in_parts,
			    bool update_pos, bool save_copyright,
			    bool skip_code)
{
  std::string help_txt;

  // TRUE means we have already seen the first block of comments.
  bool first_comments_seen = false;

  // TRUE means we are at the beginning of a comment block.
  bool begin_comment = false;

  // TRUE means we have already cached the help text.
  bool have_help_text = false;

  // TRUE means we are currently reading a comment block.
  bool in_comment = false;

  // TRUE means we should discard the first space from the input
  // (used to strip leading spaces from the help text).
  bool discard_space = true;

  int c;

  while ((c = text_getc (ffile)) != EOF)
    {
      if (update_pos)
	current_input_column++;

      if (begin_comment)
	{
	  if (c == '%' || c == '#')
	    continue;
	  else if (discard_space && c == ' ')
	    {
	      discard_space = false;
	      continue;
	    }
	  else
	    begin_comment = false;
	}

      if (in_comment)
	{
	  if (! have_help_text)
	    {
	      first_comments_seen = true;
	      help_txt += static_cast<char> (c);
	    }

	  if (c == '\n')
	    {
	      if (update_pos)
		{
		  input_line_number++;
		  current_input_column = 0;
		}

	      in_comment = false;
	      discard_space = true;

	      if (in_parts)
		{
		  if ((c = text_getc (ffile)) != EOF)
		    {
		      if (update_pos)
			current_input_column--;
		      ungetc (c, ffile);
		      if (c == '\n')
			break;
		    }
		  else
		    break;
		}
	    }
	}
      else
	{
	  switch (c)
	    {
	    case ' ':
	    case '\t':
	      if (first_comments_seen)
		have_help_text = true;
	      break;

	    case '%':
	    case '#':
	      begin_comment = true;
	      in_comment = true;
	      break;

	    case '\n':
	      if (first_comments_seen)
		have_help_text = true;
	      if (update_pos)
		{
		  input_line_number++;
		  current_input_column = 0;
		}
	      continue;

	    default:
	      if (skip_code)
		continue;
	      else
		{
		  if (update_pos)
		    current_input_column--;
		  ungetc (c, ffile);
		  goto done;
		}
	    }
	}
    }

 done:

  if (! help_txt.empty ())
    {
      if (looks_like_copyright (help_txt))
	{
	  if (save_copyright)
	    octave_comment_buffer::append (help_txt);

	  help_txt.resize (0);
	}

      if (in_parts && help_txt.empty ())
	help_txt = gobble_leading_white_space (ffile, in_parts, update_pos,
					       false, skip_code);
    }

  return help_txt;
}

std::string
get_help_from_file (const std::string& nm, bool& symbol_found,
		    std::string& file)
{
  std::string retval;

  file = fcn_file_in_path (nm);

  if (! file.empty ())
    {
      symbol_found = true;

      FILE *fptr = fopen (file.c_str (), "r");

      if (fptr)
	{
	  unwind_protect::add (safe_fclose, fptr);

	  retval = gobble_leading_white_space (fptr, true, true, false, true);

	  unwind_protect::run ();
	}
    }

  return retval;
}

std::string
get_help_from_file (const std::string& nm, bool& symbol_found)
{
  std::string file;
  return get_help_from_file (nm, symbol_found, file);
}

static int
is_function_file (FILE *ffile)
{
  int status = 0;

  long pos = ftell (ffile);

  gobble_leading_white_space (ffile, false, false, false, false);

  char buf [10];
  fgets (buf, 10, ffile);
  int len = strlen (buf);
  if (len > 8 && strncmp (buf, "function", 8) == 0
      && ! (isalnum (buf[8]) || buf[8] == '_'))
    status = 1;

  fseek (ffile, pos, SEEK_SET);

  return status;
}

static void
restore_command_history (void *)
{
  command_history::ignore_entries (! Vsaving_history);
}

static void
restore_input_stream (void *f)
{
  command_editor::set_input_stream (static_cast<FILE *> (f));
}

static bool
parse_fcn_file (const std::string& ff, bool exec_script,
		bool force_script = false)
{
  unwind_protect::begin_frame ("parse_fcn_file");

  int script_file_executed = false;

  // Open function file and parse.

  bool old_reading_fcn_file_state = reading_fcn_file;

  FILE *in_stream = command_editor::get_input_stream ();

  unwind_protect::add (restore_input_stream, in_stream);

  unwind_protect_ptr (ff_instream);

  unwind_protect_int (input_line_number);
  unwind_protect_int (current_input_column);
  unwind_protect_int (end_tokens_expected);
  unwind_protect_bool (reading_fcn_file);
  unwind_protect_bool (line_editing);
  unwind_protect_str (parent_function_name);

  input_line_number = 0;
  current_input_column = 1;
  end_tokens_expected = 0;
  reading_fcn_file = true;
  line_editing = false;
  parent_function_name = "";

  FILE *ffile = get_input_from_file (ff, 0);

  unwind_protect::add (safe_fclose, ffile);

  if (ffile)
    {
      // Check to see if this file defines a function or is just a
      // list of commands.

      if (! force_script && is_function_file (ffile))
	{
	  // FIXME -- we shouldn't need both the
	  // command_history object and the
	  // Vsaving_history variable...
	  command_history::ignore_entries ();

	  unwind_protect::add (restore_command_history, 0);

	  unwind_protect_int (Vecho_executing_commands);
	  unwind_protect_bool (Vsaving_history);
	  unwind_protect_bool (reading_fcn_file);
	  unwind_protect_bool (get_input_from_eval_string);
	  unwind_protect_bool (parser_end_of_input);

	  Vecho_executing_commands = ECHO_OFF;
	  Vsaving_history = false;
	  reading_fcn_file = true;
	  get_input_from_eval_string = false;
	  parser_end_of_input = false;

	  YY_BUFFER_STATE old_buf = current_buffer ();
	  YY_BUFFER_STATE new_buf = create_buffer (ffile);

	  unwind_protect::add (restore_input_buffer, old_buf);
	  unwind_protect::add (delete_input_buffer, new_buf);

	  switch_to_buffer (new_buf);

	  unwind_protect_ptr (curr_sym_tab);

	  reset_parser ();

	  std::string txt
	    = gobble_leading_white_space (ffile, true, true, true, false);

	  help_buf.push (txt);

	  octave_comment_buffer::append (txt);

	  // FIXME -- this should not be necessary.
	  gobble_leading_white_space (ffile, false, true, false, false);

	  int status = yyparse ();

	  if (status != 0)
	    {
	      error ("parse error while reading function file %s",
		     ff.c_str ());
	      fbi_sym_tab->clear (curr_fcn_file_name);
	    }
	}
      else if (exec_script)
	{
	  // The value of `reading_fcn_file' will be restored to the
	  // proper value when we unwind from this frame.
	  reading_fcn_file = old_reading_fcn_file_state;

	  // FIXME -- we shouldn't need both the
	  // command_history object and the
	  // Vsaving_history variable...
	  command_history::ignore_entries ();

	  unwind_protect::add (restore_command_history, 0);

	  unwind_protect_bool (Vsaving_history);
	  unwind_protect_bool (reading_script_file);

	  Vsaving_history = false;
	  reading_script_file = true;

	  octave_user_script *script = new octave_user_script (ff, ff, "");
	  octave_call_stack::push (script);
	  unwind_protect::add (octave_call_stack::unwind_pop_script, 0);

	  parse_and_execute (ffile);

	  script_file_executed = true;
	}
    }
  else
    error ("no such file, `%s'", ff.c_str ());

  unwind_protect::run_frame ("parse_fcn_file");

  return script_file_executed;
}

std::string
lookup_autoload (const std::string& nm)
{
  std::string retval;

  typedef std::map<std::string, std::string>::const_iterator am_iter;

  am_iter p = autoload_map.find (nm);

  if (p != autoload_map.end ())
    retval = load_path::find_file (p->second);

  return retval;
}

string_vector 
autoloaded_functions (void)
{
  string_vector names (autoload_map.size());

  octave_idx_type i = 0;
  typedef std::map<std::string, std::string>::const_iterator am_iter;
  for (am_iter p = autoload_map.begin (); p != autoload_map.end (); p++)
    names[i++] = p->first;

  return names;
}

string_vector
reverse_lookup_autoload (const std::string& nm)
{
  string_vector names;

  typedef std::map<std::string, std::string>::const_iterator am_iter;
  for (am_iter p = autoload_map.begin (); p != autoload_map.end (); p++)
    if (nm == p->second)
      names.append (p->first);

  return names;
}

bool
load_fcn_from_file (const std::string& nm_arg, bool exec_script)
{
  unwind_protect::begin_frame ("load_fcn_from_file");

  bool script_file_executed = false;

  std::string nm = nm_arg;

  size_t nm_len = nm.length ();

  std::string file;

  unwind_protect_bool (fcn_file_from_relative_lookup);

  fcn_file_from_relative_lookup = false;

  if (octave_env::absolute_pathname (nm)
      && ((nm_len > 4 && nm.substr (nm_len-4) == ".oct")
	  || (nm_len > 4 && nm.substr (nm_len-4) == ".mex")
	  || (nm_len > 2 && nm.substr (nm_len-2) == ".m")))
    {
      file = nm;

      nm = octave_env::base_pathname (file);
      nm = nm.substr (0, nm.find_last_of ('.'));
    }
  else
    {
      file = lookup_autoload (nm);

      if (! file.empty ())
	{
	  unwind_protect_bool (autoloading);

	  autoloading = true;
	  exec_script = true;
	}
      else
        file = load_path::find_fcn (nm);

      fcn_file_from_relative_lookup = ! octave_env::absolute_pathname (file);

      file = octave_env::make_absolute (file, octave_env::getcwd ());
    }

  int len = file.length ();

  if (len > 4 && file.substr (len-4, len-1) == ".oct")
    {
      if (octave_dynamic_loader::load_oct (nm, file, fcn_file_from_relative_lookup))
        force_link_to_function (nm);
    }
  else if (len > 4 && file.substr (len-4, len-1) == ".mex")
    {
      if (octave_dynamic_loader::load_mex (nm, file, fcn_file_from_relative_lookup))
        force_link_to_function (nm);
    }
  else if (len > 2)
    {
      // These are needed by yyparse.

      unwind_protect_str (curr_fcn_file_name);
      unwind_protect_str (curr_fcn_file_full_name);

      curr_fcn_file_name = nm;
      curr_fcn_file_full_name = file;

      script_file_executed = parse_fcn_file (file, exec_script, autoloading);

      if (! error_state)
	{
	  if (autoloading)
	    {
	      script_file_executed = false;
	      force_link_to_function (nm);
	    }
	  else if (! script_file_executed)
	    force_link_to_function (nm);
	}
    }

  unwind_protect::run_frame ("load_fcn_from_file");

  return script_file_executed;
}

bool
load_fcn_from_file (symbol_record *sym_rec, bool exec_script)
{
  return load_fcn_from_file (sym_rec->name (), exec_script);
}

DEFCMD (autoload, args, ,
  "-*- texinfo -*-\n\
@deftypefn {Built-in Function} {} autoload (@var{function}, @var{file})\n\
Define @var{function} to autoload from @var{file}.\n\
\n\
The second argument, @var{file}, should be an absolute file name and\n\
should not depend on the Octave load path.\n\
\n\
Normally, calls to @code{autoload} appear in PKG_ADD script files that\n\
are evaluated when a directory is added to the Octave's load path.  To\n\
avoid having to hardcode directory names in @var{file}, it is customary\n\
to use\n\
\n\
@example\n\
autoload (\"foo\",\n\
          fullfile (fileparts (mfilename (\"fullpath\")),\n\
                    \"bar.oct\"));\n\
@end example\n\
\n\
Uses like\n\
\n\
@example\n\
autoload (\"foo\", file_in_loadpath (\"bar.oct\"))\n\
@end example\n\
\n\
@noindent\n\
are strongly discouraged.\n\
\n\
With no arguments, return a structure containing the current autoload map.\n\
@seealso{PKG_ADD}\n\
@end deftypefn")
{
  octave_value retval;

  int nargin = args.length ();

  if (nargin == 0)
    {
      Cell func_names (dim_vector (autoload_map.size ()), 1);
      Cell file_names (dim_vector (autoload_map.size ()), 1);

      octave_idx_type i = 0;
      typedef std::map<std::string, std::string>::const_iterator am_iter;
      for (am_iter p = autoload_map.begin (); p != autoload_map.end (); p++)
	{
	  func_names(i) = p->first;
	  file_names(i) = p->second;

	  i++;
	}

      Octave_map m;

      m.assign ("function", func_names);
      m.assign ("file", file_names);

      retval = m;
    }
  else if (nargin == 2)
    {
      string_vector argv = args.make_argv ("autoload");

      if (! error_state)
        {
	  std::string nm = argv[2];

	  if (! octave_env::absolute_pathname (nm))
	    warning_with_id ("Octave:autoload-relative-file-name",
			     "autoload: `%s' is not an absolute file name",
			     nm.c_str ());

	  autoload_map[argv[1]] = nm;
	}
    }
  else
    print_usage ();

  return retval;
}

void
source_file (const std::string& file_name, const std::string& context)
{
  std::string file_full_name = file_ops::tilde_expand (file_name);

  unwind_protect::begin_frame ("source_file");

  unwind_protect_str (curr_fcn_file_name);
  unwind_protect_str (curr_fcn_file_full_name);

  curr_fcn_file_name = file_name;
  curr_fcn_file_full_name = file_full_name;

  if (! context.empty ())
    {
      unwind_protect_ptr (curr_sym_tab);

      if (context == "caller")
	curr_sym_tab = curr_caller_sym_tab;
      else if (context == "base")
	curr_sym_tab = top_level_sym_tab;
      else
	error ("source: context must be \"caller\" or \"base\"");
    }      

  if (! error_state)
    {
      parse_fcn_file (file_full_name, true, true);

      if (error_state)
	error ("source: error sourcing file `%s'",
	       file_full_name.c_str ());
    }

  unwind_protect::run_frame ("source_file");
}

DEFUN (mfilename, args, ,
  "-*- texinfo -*-\n\
@deftypefn {Built-in Function} {} mfilename ()\n\
@deftypefnx {Built-in Function} {} mfilename (@code{\"fullpath\"})\n\
@deftypefnx {Built-in Function} {} mfilename (@code{\"fullpathext\"})\n\
Return the name of the currently executing file.  At the top-level,\n\
return the empty string.  Given the argument @code{\"fullpath\"},\n\
include the directory part of the file name, but not the extension.\n\
Given the argument @code{\"fullpathext\"}, include the directory part\n\
of the file name and the extension.\n\
@end deftypefn")
{
  octave_value retval;

  int nargin = args.length ();

  if (nargin > 1)
    {
      print_usage ();
      return retval;
    }

  std::string arg;

  if (nargin == 1)
    {
      arg = args(0).string_value ();

      if (error_state)
	{
	  error ("mfilename: expecting argument to be a character string");
	  return retval;
	}
    }

  std::string fname;

  octave_function *fcn = octave_call_stack::caller_user_script_or_function ();

  if (fcn)
    {
      fname = fcn->fcn_file_name ();

      if (fname.empty ())
        fname = fcn->name ();
    }

  if (arg == "fullpathext")
    retval = fname;
  else
    {
      size_t dpos = fname.rfind (file_ops::dir_sep_char);
      size_t epos = fname.rfind ('.');

      if (epos <= dpos)
        epos = NPOS;

      fname = (epos != NPOS) ? fname.substr (0, epos) : fname;

      if (arg == "fullpath")
	retval = fname;
      else
        retval = (dpos != NPOS) ? fname.substr (dpos+1) : fname;
    }

  return retval;
}


DEFUN (source, args, ,
  "-*- texinfo -*-\n\
@deftypefn {Built-in Function} {} source (@var{file})\n\
Parse and execute the contents of @var{file}.  This is equivalent to\n\
executing commands from a script file, but without requiring the file to\n\
be named @file{@var{file}.m}.\n\
@end deftypefn")
{
  octave_value_list retval;

  int nargin = args.length ();

  if (nargin == 1 || nargin == 2)
    {
      std::string file_name = args(0).string_value ();

      if (! error_state)
	{
	  std::string context;

	  if (nargin == 2)
	    context = args(1).string_value ();

	  if (! error_state)
	    source_file (file_name, context);
	  else
	    error ("source: expecting context to be character string");
	}
      else
	error ("source: expecting file name as argument");
    }
  else
    print_usage ();

  return retval;
}

// Evaluate an Octave function (built-in or interpreted) and return
// the list of result values.  NAME is the name of the function to
// call.  ARGS are the arguments to the function.  NARGOUT is the
// number of output arguments expected. 

octave_value_list
feval (const std::string& name, const octave_value_list& args, int nargout)
{
  octave_value_list retval;

  octave_function *fcn = is_valid_function (name, "feval", 1);

  if (fcn)
    retval = fcn->do_multi_index_op (nargout, args);

  return retval;
}

octave_value_list
feval (octave_function *fcn, const octave_value_list& args, int nargout)
{
  octave_value_list retval;

  if (fcn)
    retval = fcn->do_multi_index_op (nargout, args);

  return retval;
}

static octave_value_list
get_feval_args (const octave_value_list& args)
{
  int tmp_nargin = args.length () - 1;

  octave_value_list retval (tmp_nargin, octave_value ());

  for (int i = 0; i < tmp_nargin; i++)
    retval(i) = args(i+1);

  string_vector arg_names = args.name_tags ();

  if (! arg_names.empty ())
    {
      // tmp_nargin and arg_names.length () - 1 may differ if
      // we are passed all_va_args.

      int n = arg_names.length () - 1;

      int len = n > tmp_nargin ? tmp_nargin : n;

      string_vector tmp_arg_names (len);

      for (int i = 0; i < len; i++)
	tmp_arg_names(i) = arg_names(i+1);

      retval.stash_name_tags (tmp_arg_names);
    }

  return retval;
}


// Evaluate an Octave function (built-in or interpreted) and return
// the list of result values.  The first element of ARGS should be a
// string containing the name of the function to call, then the rest
// are the actual arguments to the function.  NARGOUT is the number of
// output arguments expected.

octave_value_list
feval (const octave_value_list& args, int nargout)
{
  octave_value_list retval;

  int nargin = args.length ();

  if (nargin > 0)
    {
      octave_value f_arg = args(0);

      if (f_arg.is_string ())
        {
	  std::string name = f_arg.string_value ();

	  if (! error_state)
	    {
	      octave_value_list tmp_args = get_feval_args (args);

	      retval = feval (name, tmp_args, nargout);
	    }
	}
      else
	{
	  octave_function *fcn = f_arg.function_value ();

	  if (fcn)
	    {
	      octave_value_list tmp_args = get_feval_args (args);

	      retval = feval (fcn, tmp_args, nargout);
	    }
	}
    }

  return retval;
}

DEFUN (feval, args, nargout,
  "-*- texinfo -*-\n\
@deftypefn {Built-in Function} {} feval (@var{name}, @dots{})\n\
Evaluate the function named @var{name}.  Any arguments after the first\n\
are passed on to the named function.  For example,\n\
\n\
@example\n\
feval (\"acos\", -1)\n\
     @result{} 3.1416\n\
@end example\n\
\n\
@noindent\n\
calls the function @code{acos} with the argument @samp{-1}.\n\
\n\
The function @code{feval} is necessary in order to be able to write\n\
functions that call user-supplied functions, because Octave does not\n\
have a way to declare a pointer to a function (like C) or to declare a\n\
special kind of variable that can be used to hold the name of a function\n\
(like @code{EXTERNAL} in Fortran).  Instead, you must refer to functions\n\
by name, and use @code{feval} to call them.\n\
@end deftypefn")
{
  octave_value_list retval;

  int nargin = args.length ();

  if (nargin > 0)
    retval = feval (args, nargout);
  else
    print_usage ();

  return retval;
}

octave_value_list
eval_string (const std::string& s, bool silent, int& parse_status, int nargout)
{
  octave_value_list retval;

  unwind_protect::begin_frame ("eval_string");

  unwind_protect_bool (get_input_from_eval_string);
  unwind_protect_bool (input_from_eval_string_pending);
  unwind_protect_bool (parser_end_of_input);
  unwind_protect_bool (line_editing);
  unwind_protect_str (current_eval_string);

  get_input_from_eval_string = true;
  input_from_eval_string_pending = true;
  parser_end_of_input = false;
  line_editing = false;

  current_eval_string = s;

  unwind_protect_ptr (global_command);

  YY_BUFFER_STATE old_buf = current_buffer ();
  YY_BUFFER_STATE new_buf = create_buffer (0);

  unwind_protect::add (restore_input_buffer, old_buf);
  unwind_protect::add (delete_input_buffer, new_buf);

  switch_to_buffer (new_buf);

  unwind_protect_ptr (curr_sym_tab);

  do
    {
      reset_parser ();

      parse_status = yyparse ();

      tree_statement_list *command = global_command;

      if (parse_status == 0)
        {
	  if (command)
	    {
	      retval = command->eval (silent, nargout);

	      delete command;

	      command = 0;

	      if (error_state
		  || tree_return_command::returning
		  || tree_break_command::breaking
		  || tree_continue_command::continuing)
		break;
	    }
	  else if (parser_end_of_input)
	    break;
        }
    }
  while (parse_status == 0);

  unwind_protect::run_frame ("eval_string");

  return retval;
}

octave_value
eval_string (const std::string& s, bool silent, int& parse_status)
{
  octave_value retval;

  octave_value_list tmp = eval_string (s, silent, parse_status, 1);

  if (! tmp.empty ())
    retval = tmp(0);

  return retval;
}

static octave_value_list
eval_string (const octave_value& arg, bool silent, int& parse_status,
	     int nargout)
{
  std::string s = arg.string_value ();

  if (error_state)
    {
      error ("eval: expecting std::string argument");
      return octave_value (-1);
    }

  return eval_string (s, silent, parse_status, nargout);
}

DEFUN (eval, args, nargout,
  "-*- texinfo -*-\n\
@deftypefn {Built-in Function} {} eval (@var{try}, @var{catch})\n\
Parse the string @var{try} and evaluate it as if it were an Octave\n\
program.  If that fails, evaluate the optional string @var{catch}.\n\
The string @var{try} is evaluated in the current context,\n\
so any results remain available after @code{eval} returns.\n\
\n\
The following example makes the variable @var{a} with the approximate\n\
value 3.1416 available.\n\
\n\
@example\n\
eval(\"a = acos(-1);\");\n\
@end example\n\
\n\
If an error occurs during the evaluation of @var{try} the @var{catch}\n\
string is evaluated, as the following example shows.\n\
\n\
@example\n\
eval ('error (\"This is a bad example\");',\n\
      'printf (\"This error occured:\\n%s\", lasterr ());');\n\
     @print{} This error occured:\n\
        error: This is a bad example\n\
@end example\n\
@end deftypefn")
{
  octave_value_list retval;

  int nargin = args.length ();

  if (nargin > 0)
    {
      unwind_protect::begin_frame ("Feval");

      if (nargin > 1)
	{
	  unwind_protect_int (buffer_error_messages);
	  buffer_error_messages++;
	}

      int parse_status = 0;

      octave_value_list tmp = eval_string (args(0), nargout > 0,
					   parse_status, nargout);

      if (nargout > 0)
	retval = tmp;

      if (nargin > 1 && (parse_status != 0 || error_state))
	{
	  error_state = 0;

	  // Set up for letting the user print any messages from
	  // errors that occurred in the first part of this eval().

	  buffer_error_messages--;

	  eval_string (args(1), 0, parse_status, nargout);

	  retval = octave_value_list ();
	}

      unwind_protect::run_frame ("Feval");
    }
  else
    print_usage ();

  return retval;
}

DEFUN (assignin, args, ,
  "-*- texinfo -*-\n\
@deftypefn {Built-in Function} {} assignin (@var{context}, @var{varname}, @var{value})\n\
Assign @var{value} to @var{varname} in context @var{context}, which\n\
may be either @code{\"base\"} or @code{\"caller\"}.\n\
@end deftypefn")
{
  octave_value_list retval;

  int nargin = args.length ();

  if (nargin == 3)
    {
      std::string context = args(0).string_value ();

      if (! error_state)
        {
	  unwind_protect::begin_frame ("Fassignin");

	  unwind_protect_ptr (curr_sym_tab);

	  if (context == "caller")
	    curr_sym_tab = curr_caller_sym_tab;
	  else if (context == "base")
	    curr_sym_tab = top_level_sym_tab;
	  else
	    error ("assignin: context must be \"caller\" or \"base\"");

	  if (! error_state)
	    {
	      std::string nm = args(1).string_value ();

	      if (! error_state)
		{
		  if (valid_identifier (nm))
		    {
		      symbol_record *sr = curr_sym_tab->lookup (nm, true);

		      if (sr)
			{
			  tree_identifier *id = new tree_identifier (sr);
			  tree_constant *rhs = new tree_constant (args(2));
		      
			  tree_simple_assignment tsa (id, rhs);

			  tsa.rvalue ();
			}
		    }
		  else
		    error ("assignin: invalid variable name");
		}
	      else
		error ("assignin: expecting variable name as second argument");
	    }

	  unwind_protect::run_frame ("Fassignin");
	}
      else
        error ("assignin: expecting string as first argument");
    }
  else
    print_usage ();

  return retval;
}

DEFUN (evalin, args, nargout,
  "-*- texinfo -*-\n\
@deftypefn {Built-in Function} {} evalin (@var{context}, @var{try}, @var{catch})\n\
Like @code{eval}, except that the expressions are evaluated in the\n\
context @var{context}, which may be either @code{\"caller\"} or\n\
@code{\"base\"}.\n\
@end deftypefn")
{
  octave_value_list retval;

  int nargin = args.length ();

  if (nargin > 1)
    {
      std::string context = args(0).string_value ();

      if (! error_state)
        {
	  unwind_protect::begin_frame ("Fevalin");

	  unwind_protect_ptr (curr_sym_tab);

	  if (context == "caller")
	    curr_sym_tab = curr_caller_sym_tab;
	  else if (context == "base")
	    curr_sym_tab = top_level_sym_tab;
	  else
	    error ("evalin: context must be \"caller\" or \"base\"");

	  if (! error_state)
	    {
	      if (nargin > 2)
	        {
		  unwind_protect_int (buffer_error_messages);
		  buffer_error_messages++;
		}

	      int parse_status = 0;

	      octave_value_list tmp = eval_string (args(1), nargout > 0,
						   parse_status, nargout);

	      if (nargout > 0)
		retval = tmp;

	      if (nargin > 2 && (parse_status != 0 || error_state))
		{
		  error_state = 0;

		  // Set up for letting the user print any messages from
		  // errors that occurred in the first part of this eval().

		  buffer_error_messages--;

		  eval_string (args(2), 0, parse_status, nargout);

		  retval = octave_value_list ();
		}
	    }

	  unwind_protect::run_frame ("Fevalin");
	}
      else
        error ("evalin: expecting string as first argument");
    }
  else
    print_usage ();

  return retval;
}

/*
;;; Local Variables: ***
;;; mode: text ***
;;; End: ***
*/