Entry
Compiler: Syntax:Backus-Naur form:Yacc: Windows: Bison: Can you give simple example with Bison?
Oct 21st, 2003 20:34
Knud van Eeden,
----------------------------------------------------------------------
--- Knud van Eeden --- 22 October 2003 - 02:09 am --------------------
Compiler: Syntax:Backus-Naur form:Yacc: Windows: Bison: Can you give
simple example with Bison?
---
---
A simple example to use YACC (=bison.exe), and LEX (=flex.exe) on a
Windows system.
---
1. Download
1. flex.exe
2. bison.exe
3. bison.simple
from
http://www.monmouth.com/~wstreett/lex-yacc/lex-yacc.html
---
2. Create a text file, using your favorite text editor (e.g. TSE,
vi, notepad, ...), containing the following text:
--- cut here ---------------------------------------------------------
%{
#include <ctype.h>
%}
%token NUMBER
%left '+' '-'
%%
line : expression '\n' {printf( "%d\n", $1 ); }
expression : expression '+' expression { $$ = $1 + $3; }
| expression '-' expression { $$ = $1 - $3; }
| '(' expression ')' { $$ = $2; }
| NUMBER { $$ = $1; }
;
%%
yylex() {
int c;
c = getchar();
if ( isdigit( c ) ) {
yylval = c - '0';
return NUMBER;
}
return( c );
}
--- cut here ---------------------------------------------------------
3. Save this text file, e.g. as 'myfilename.y'
(for example in the same directory as bison.exe and bison.simple)
4. Make sure you have files
bison.exe
and
bison.simple
in the same directory
5. Now compile this program by typing
bison.exe myfilename.y
on the MSDOS command line
6. If this successfully compiles, it will generate program called
myfilename_tab.c
7. An example of the content of this file 'myfilename_tab.c',
using the example here above can be seen below.
8. You will manually have to add some extra text,
1. Add a 'main()' routine to this file ''myfilename_tab.c',
Minimally containing
main() {
yyparse();
}
2. Add an error procedure 'yyerror()' to this
file ''myfilename_tab.c',
Minimally containing
yyerror( s )
char *s;
{
printf ("%s\n", s);
}
9. Compile this 'myfilename_tab.c' in the usual way, e.g. using
your favorite C or C++ compiler.
(Borland command line compiler, Borland C++Builder, Microsoft Visual
C++, ...)
---
e.g. using the free Borland command line compiler, type on the MSDOS
command line:
c:\borland\bcc55\bin\bcc32.exe -Ic:\borland\bcc55\include -
Lc:\borland\bcc55\lib myfilename_tab.c
(note: this should all be on one line)
10. This will create, if successfully compiled, an .exe file, called
myfilename_tab.exe
11. To use this .exe file, type the .exe filename,
followed by enter, and then some expression
containing digits and '+' and '-'.
e.g.
1. type the command
myfilename_tab.exe
2. then press <ENTER>
3. then type e.g.
3+4
(so *no* spaces in this simple example)
4. then press again <ENTER>
5. that will show 7
6. Pressing again <ENTER> will give the error
'parse error', and you will exit.
---
12. Trouble shooting:
1. Note, if you type e.g.
myfilename_tab.exe 3+4
then <ENTER>, this is not going to work.
You should first type
myfilename_tab.exe
then <ENTER>
then 3+4 (with no spaces)
then <ENTER>
then you should see '7'
2. If you get unresolved '_main', it means you should include the
'main()' function in your file myfilename_tab.c
3. If you get unresolved '_yyerror', it means you should include
the 'yyerror()' function in your file myfilename_tab.c
4. If you get a 'parse error', it means that the input tokens are
not recognized.
---
---
Internet: see also:
http://docs.freebsd.org/info/bison/bison.info.RPN_Calc.html
---
---
12. Below the full generated source of the above example.
--- cut here ---------------------------------------------------------
/* A Bison parser, made from ddd.y with Bison version GNU Bison
version 1.24
*/
#define YYBISON 1 /* Identify Bison output. */
#define NUMBER 258
#line 1 "ddd.y"
#include <ctype.h>
#include <stdio.h>
#ifndef YYLTYPE
typedef
struct yyltype
{
int timestamp;
int first_line;
int first_column;
int last_line;
int last_column;
char *text;
}
yyltype;
#define YYLTYPE yyltype
#endif
#ifndef YYSTYPE
#define YYSTYPE int
#endif
#include <stdio.h>
#ifndef __cplusplus
#ifndef __STDC__
#define const
#endif
#endif
#define YYFINAL 13
#define YYFLAG -32768
#define YYNTBASE 9
#define YYTRANSLATE(x) ((unsigned)(x) <= 258 ? yytranslate[x] : 11)
static const char yytranslate[] = { 0,
2, 2, 2, 2, 2, 2, 2, 2, 2, 6,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 7,
8, 2, 4, 2, 5, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 1, 2, 3
};
#if YYDEBUG != 0
static const short yyprhs[] = { 0,
0, 3, 7, 11, 15
};
static const short yyrhs[] = { 10,
6, 0, 10, 4, 10, 0, 10, 5, 10, 0,
7, 10, 8, 0, 3, 0
};
#endif
#if YYDEBUG != 0
static const short yyrline[] = { 0,
15, 17, 19, 21, 23
};
static const char * const yytname[] =
{ "$","error","$undefined.","NUMBER",
"'+'","'-'","'\\n'","'('","')'","line","expression",""
};
#endif
static const short yyr1[] = { 0,
9, 10, 10, 10, 10
};
static const short yyr2[] = { 0,
2, 3, 3, 3, 1
};
static const short yydefact[] = { 0,
5, 0, 0, 0, 0, 0, 1, 4, 2, 3,
0, 0, 0
};
static const short yydefgoto[] = { 11,
3
};
static const short yypact[] = { 4,
-32768, 4, 8, -4, 4, 4,-32768,-32768,-32768,-32768,
3, 9,-32768
};
static const short yypgoto[] = {-32768,
0
};
#define YYLAST 14
static const short yytable[] = { 5,
6, 4, 12, 8, 9, 10, 1, 0, 13, 0,
2, 5, 6, 7
};
static const short yycheck[] = { 4,
5, 2, 0, 8, 5, 6, 3, -1, 0, -1,
7, 4, 5, 6
};
/* -*-C-*- Note some compilers choke on comments on `#line' lines. */
#line 3 "bison.simple"
/* Skeleton output parser for bison,
Copyright (C) 1984, 1989, 1990 Free Software Foundation, Inc.
This program 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.
This program 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 this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
/* As a special exception, when this file is copied by Bison into a
Bison output file, you may use that output file without restriction.
This special exception was added by the Free Software Foundation
in version 1.24 of Bison. */
#ifndef alloca
#ifdef __GNUC__
#define alloca __builtin_alloca
#else /* not GNU C. */
#if (!defined (__STDC__) && defined (sparc)) || defined (__sparc__) ||
defined (__sparc) || defined (__sgi)
#include <alloca.h>
#else /* not sparc */
#if defined (MSDOS) && !defined (__TURBOC__)
#include <malloc.h>
#else /* not MSDOS, or __TURBOC__ */
#if defined(_AIX)
#include <malloc.h>
#pragma alloca
#else /* not MSDOS, __TURBOC__, or _AIX */
#ifdef __hpux
#ifdef __cplusplus
extern "C" {
void *alloca (unsigned int);
};
#else /* not __cplusplus */
void *alloca ();
#endif /* not __cplusplus */
#endif /* __hpux */
#endif /* not _AIX */
#endif /* not MSDOS, or __TURBOC__ */
#endif /* not sparc. */
#endif /* not GNU C. */
#endif /* alloca not defined. */
/* This is the parser code that is written into each bison parser
when the %semantic_parser declaration is not specified in the
grammar.
It was written by Richard Stallman by simplifying the hairy parser
used when %semantic_parser is specified. */
/* Note: there must be only one dollar sign in this file.
It is replaced by the list of actions, each action
as one case of the switch. */
#define yyerrok (yyerrstatus = 0)
#define yyclearin (yychar = YYEMPTY)
#define YYEMPTY -2
#define YYEOF 0
#define YYACCEPT return(0)
#define YYABORT return(1)
#define YYERROR goto yyerrlab1
/* Like YYERROR except do call yyerror.
This remains here temporarily to ease the
transition to the new meaning of YYERROR, for GCC.
Once GCC version 2 has supplanted version 1, this can go. */
#define YYFAIL goto yyerrlab
#define YYRECOVERING() (!!yyerrstatus)
#define YYBACKUP(token, value) \
do \
if (yychar == YYEMPTY && yylen == 1) \
{ yychar = (token), yylval = (value); \
yychar1 = YYTRANSLATE (yychar); \
YYPOPSTACK; \
goto yybackup; \
} \
else \
{ yyerror ("syntax error: cannot back up"); YYERROR; } \
while (0)
#define YYTERROR 1
#define YYERRCODE 256
#ifndef YYPURE
#define YYLEX yylex()
#endif
#ifdef YYPURE
#ifdef YYLSP_NEEDED
#ifdef YYLEX_PARAM
#define YYLEX yylex(&yylval, &yylloc, YYLEX_PARAM)
#else
#define YYLEX yylex(&yylval, &yylloc)
#endif
#else /* not YYLSP_NEEDED */
#ifdef YYLEX_PARAM
#define YYLEX yylex(&yylval, YYLEX_PARAM)
#else
#define YYLEX yylex(&yylval)
#endif
#endif /* not YYLSP_NEEDED */
#endif
/* If nonreentrant, generate the variables here */
#ifndef YYPURE
int yychar; /* the lookahead symbol
*/
YYSTYPE yylval; /* the semantic value of the
*/
/* lookahead symbol
*/
#ifdef YYLSP_NEEDED
YYLTYPE yylloc; /* location data for the lookahead
*/
/* symbol
*/
#endif
int yynerrs; /* number of parse errors so
far */
#endif /* not YYPURE */
#if YYDEBUG != 0
int yydebug; /* nonzero means print parse trace
*/
/* Since this is uninitialized, it does not stop multiple parsers
from coexisting. */
#endif
/* YYINITDEPTH indicates the initial size of the parser's stacks
*/
#ifndef YYINITDEPTH
#define YYINITDEPTH 200
#endif
/* YYMAXDEPTH is the maximum size the stacks can grow to
(effective only if the built-in stack extension method is used).
*/
#if YYMAXDEPTH == 0
#undef YYMAXDEPTH
#endif
#ifndef YYMAXDEPTH
#define YYMAXDEPTH 10000
#endif
/* Prevent warning if -Wstrict-prototypes. */
#ifdef __GNUC__
int yyparse (void);
#endif
#if __GNUC__ > 1 /* GNU C and GNU C++ define this. */
#define __yy_memcpy(FROM,TO,COUNT) __builtin_memcpy(TO,FROM,COUNT)
#else /* not GNU C or C++ */
#ifndef __cplusplus
/* This is the most reliable way to avoid incompatibilities
in available built-in functions on various systems. */
static void
__yy_memcpy (from, to, count)
char *from;
char *to;
int count;
{
register char *f = from;
register char *t = to;
register int i = count;
while (i-- > 0)
*t++ = *f++;
}
#else /* __cplusplus */
/* This is the most reliable way to avoid incompatibilities
in available built-in functions on various systems. */
static void
__yy_memcpy (char *from, char *to, int count)
{
register char *f = from;
register char *t = to;
register int i = count;
while (i-- > 0)
*t++ = *f++;
}
#endif
#endif
#line 192 "bison.simple"
/* The user can define YYPARSE_PARAM as the name of an argument to be
passed
into yyparse. The argument should have type void *.
It should actually point to an object.
Grammar actions can access the variable by casting it
to the proper pointer type. */
#ifdef YYPARSE_PARAM
#define YYPARSE_PARAM_DECL void *YYPARSE_PARAM;
#else
#define YYPARSE_PARAM
#define YYPARSE_PARAM_DECL
#endif
int
yyparse(YYPARSE_PARAM)
YYPARSE_PARAM_DECL
{
register int yystate;
register int yyn;
register short *yyssp;
register YYSTYPE *yyvsp;
int yyerrstatus; /* number of tokens to shift before error
messages enabled */
int yychar1 = 0; /* lookahead token as an internal
(translated) token number */
short yyssa[YYINITDEPTH]; /* the state stack
*/
YYSTYPE yyvsa[YYINITDEPTH]; /* the semantic value stack
*/
short *yyss = yyssa; /* refer to the stacks thru separate
pointers */
YYSTYPE *yyvs = yyvsa; /* to allow yyoverflow to reallocate
them elsewhere */
#ifdef YYLSP_NEEDED
YYLTYPE yylsa[YYINITDEPTH]; /* the location stack
*/
YYLTYPE *yyls = yylsa;
YYLTYPE *yylsp;
#define YYPOPSTACK (yyvsp--, yyssp--, yylsp--)
#else
#define YYPOPSTACK (yyvsp--, yyssp--)
#endif
int yystacksize = YYINITDEPTH;
#ifdef YYPURE
int yychar;
YYSTYPE yylval;
int yynerrs;
#ifdef YYLSP_NEEDED
YYLTYPE yylloc;
#endif
#endif
YYSTYPE yyval; /* the variable used to return
*/
/* semantic values from the action
*/
/* routines
*/
int yylen;
#if YYDEBUG != 0
if (yydebug)
fprintf(stderr, "Starting parse\n");
#endif
yystate = 0;
yyerrstatus = 0;
yynerrs = 0;
yychar = YYEMPTY; /* Cause a token to be read. */
/* Initialize stack pointers.
Waste one element of value and location stack
so that they stay on the same level as the state stack.
The wasted elements are never initialized. */
yyssp = yyss - 1;
yyvsp = yyvs;
#ifdef YYLSP_NEEDED
yylsp = yyls;
#endif
/* Push a new state, which is found in yystate . */
/* In all cases, when you get here, the value and location stacks
have just been pushed. so pushing a state here evens the stacks. */
yynewstate:
*++yyssp = yystate;
if (yyssp >= yyss + yystacksize - 1)
{
/* Give user a chance to reallocate the stack */
/* Use copies of these so that the &'s don't force the real ones
into memory. */
YYSTYPE *yyvs1 = yyvs;
short *yyss1 = yyss;
#ifdef YYLSP_NEEDED
YYLTYPE *yyls1 = yyls;
#endif
/* Get the current used size of the three stacks, in elements.
*/
int size = yyssp - yyss + 1;
#ifdef yyoverflow
/* Each stack pointer address is followed by the size of
the data in use in that stack, in bytes. */
#ifdef YYLSP_NEEDED
/* This used to be a conditional around just the two extra args,
but that might be undefined if yyoverflow is a macro. */
yyoverflow("parser stack overflow",
&yyss1, size * sizeof (*yyssp),
&yyvs1, size * sizeof (*yyvsp),
&yyls1, size * sizeof (*yylsp),
&yystacksize);
#else
yyoverflow("parser stack overflow",
&yyss1, size * sizeof (*yyssp),
&yyvs1, size * sizeof (*yyvsp),
&yystacksize);
#endif
yyss = yyss1; yyvs = yyvs1;
#ifdef YYLSP_NEEDED
yyls = yyls1;
#endif
#else /* no yyoverflow */
/* Extend the stack our own way. */
if (yystacksize >= YYMAXDEPTH)
{
yyerror("parser stack overflow");
return 2;
}
yystacksize *= 2;
if (yystacksize > YYMAXDEPTH)
yystacksize = YYMAXDEPTH;
yyss = (short *) alloca (yystacksize * sizeof (*yyssp));
__yy_memcpy ((char *)yyss1, (char *)yyss, size * sizeof
(*yyssp));
yyvs = (YYSTYPE *) alloca (yystacksize * sizeof (*yyvsp));
__yy_memcpy ((char *)yyvs1, (char *)yyvs, size * sizeof
(*yyvsp));
#ifdef YYLSP_NEEDED
yyls = (YYLTYPE *) alloca (yystacksize * sizeof (*yylsp));
__yy_memcpy ((char *)yyls1, (char *)yyls, size * sizeof
(*yylsp));
#endif
#endif /* no yyoverflow */
yyssp = yyss + size - 1;
yyvsp = yyvs + size - 1;
#ifdef YYLSP_NEEDED
yylsp = yyls + size - 1;
#endif
#if YYDEBUG != 0
if (yydebug)
fprintf(stderr, "Stack size increased to %d\n", yystacksize);
#endif
if (yyssp >= yyss + yystacksize - 1)
YYABORT;
}
#if YYDEBUG != 0
if (yydebug)
fprintf(stderr, "Entering state %d\n", yystate);
#endif
goto yybackup;
yybackup:
/* Do appropriate processing given the current state. */
/* Read a lookahead token if we need one and don't already have one.
*/
/* yyresume: */
/* First try to decide what to do without reference to lookahead
token. */
yyn = yypact[yystate];
if (yyn == YYFLAG)
goto yydefault;
/* Not known => get a lookahead token if don't already have one. */
/* yychar is either YYEMPTY or YYEOF
or a valid token in external form. */
if (yychar == YYEMPTY)
{
#if YYDEBUG != 0
if (yydebug)
fprintf(stderr, "Reading a token: ");
#endif
yychar = YYLEX;
}
/* Convert token to internal form (in yychar1) for indexing tables
with */
if (yychar <= 0) /* This means end of input. */
{
yychar1 = 0;
yychar = YYEOF; /* Don't call YYLEX any more */
#if YYDEBUG != 0
if (yydebug)
fprintf(stderr, "Now at end of input.\n");
#endif
}
else
{
yychar1 = YYTRANSLATE(yychar);
#if YYDEBUG != 0
if (yydebug)
{
fprintf (stderr, "Next token is %d (%s", yychar, yytname
[yychar1]);
/* Give the individual parser a way to print the precise
meaning
of a token, for further debugging info. */
#ifdef YYPRINT
YYPRINT (stderr, yychar, yylval);
#endif
fprintf (stderr, ")\n");
}
#endif
}
yyn += yychar1;
if (yyn < 0 || yyn > YYLAST || yycheck[yyn] != yychar1)
goto yydefault;
yyn = yytable[yyn];
/* yyn is what to do for this token type in this state.
Negative => reduce, -yyn is rule number.
Positive => shift, yyn is new state.
New state is final state => don't bother to shift,
just return success.
0, or most negative number => error. */
if (yyn < 0)
{
if (yyn == YYFLAG)
goto yyerrlab;
yyn = -yyn;
goto yyreduce;
}
else if (yyn == 0)
goto yyerrlab;
if (yyn == YYFINAL)
YYACCEPT;
/* Shift the lookahead token. */
#if YYDEBUG != 0
if (yydebug)
fprintf(stderr, "Shifting token %d (%s), ", yychar, yytname
[yychar1]);
#endif
/* Discard the token being shifted unless it is eof. */
if (yychar != YYEOF)
yychar = YYEMPTY;
*++yyvsp = yylval;
#ifdef YYLSP_NEEDED
*++yylsp = yylloc;
#endif
/* count tokens shifted since error; after three, turn off error
status. */
if (yyerrstatus) yyerrstatus--;
yystate = yyn;
goto yynewstate;
/* Do the default action for the current state. */
yydefault:
yyn = yydefact[yystate];
if (yyn == 0)
goto yyerrlab;
/* Do a reduction. yyn is the number of a rule to reduce with. */
yyreduce:
yylen = yyr2[yyn];
if (yylen > 0)
yyval = yyvsp[1-yylen]; /* implement default value of the action */
#if YYDEBUG != 0
if (yydebug)
{
int i;
fprintf (stderr, "Reducing via rule %d (line %d), ",
yyn, yyrline[yyn]);
/* Print the symbols being reduced, and their result. */
for (i = yyprhs[yyn]; yyrhs[i] > 0; i++)
fprintf (stderr, "%s ", yytname[yyrhs[i]]);
fprintf (stderr, " -> %s\n", yytname[yyr1[yyn]]);
}
#endif
switch (yyn) {
case 1:
#line 15 "ddd.y"
{printf( "%d\n", yyvsp[-1] ); ;
break;}
case 2:
#line 17 "ddd.y"
{ yyval = yyvsp[-2] + yyvsp[0]; ;
break;}
case 3:
#line 19 "ddd.y"
{ yyval = yyvsp[-2] - yyvsp[0]; ;
break;}
case 4:
#line 21 "ddd.y"
{ yyval = yyvsp[-1]; ;
break;}
case 5:
#line 23 "ddd.y"
{ yyval = yyvsp[0]; ;
break;}
}
/* the action file gets copied in in place of this dollarsign */
#line 487 "bison.simple"
yyvsp -= yylen;
yyssp -= yylen;
#ifdef YYLSP_NEEDED
yylsp -= yylen;
#endif
#if YYDEBUG != 0
if (yydebug)
{
short *ssp1 = yyss - 1;
fprintf (stderr, "state stack now");
while (ssp1 != yyssp)
fprintf (stderr, " %d", *++ssp1);
fprintf (stderr, "\n");
}
#endif
*++yyvsp = yyval;
#ifdef YYLSP_NEEDED
yylsp++;
if (yylen == 0)
{
yylsp->first_line = yylloc.first_line;
yylsp->first_column = yylloc.first_column;
yylsp->last_line = (yylsp-1)->last_line;
yylsp->last_column = (yylsp-1)->last_column;
yylsp->text = 0;
}
else
{
yylsp->last_line = (yylsp+yylen-1)->last_line;
yylsp->last_column = (yylsp+yylen-1)->last_column;
}
#endif
/* Now "shift" the result of the reduction.
Determine what state that goes to,
based on the state we popped back to
and the rule number reduced by. */
yyn = yyr1[yyn];
yystate = yypgoto[yyn - YYNTBASE] + *yyssp;
if (yystate >= 0 && yystate <= YYLAST && yycheck[yystate] == *yyssp)
yystate = yytable[yystate];
else
yystate = yydefgoto[yyn - YYNTBASE];
goto yynewstate;
yyerrlab: /* here on detecting error */
if (! yyerrstatus)
/* If not already recovering from an error, report this error. */
{
++yynerrs;
#ifdef YYERROR_VERBOSE
yyn = yypact[yystate];
if (yyn > YYFLAG && yyn < YYLAST)
{
int size = 0;
char *msg;
int x, count;
count = 0;
/* Start X at -yyn if nec to avoid negative indexes in
yycheck. */
for (x = (yyn < 0 ? -yyn : 0);
x < (sizeof(yytname) / sizeof(char *)); x++)
if (yycheck[x + yyn] == x)
size += strlen(yytname[x]) + 15, count++;
msg = (char *) malloc(size + 15);
if (msg != 0)
{
strcpy(msg, "parse error");
if (count < 5)
{
count = 0;
for (x = (yyn < 0 ? -yyn : 0);
x < (sizeof(yytname) / sizeof(char *)); x++)
if (yycheck[x + yyn] == x)
{
strcat(msg, count == 0 ? ", expecting `" : "
or `");
strcat(msg, yytname[x]);
strcat(msg, "'");
count++;
}
}
yyerror(msg);
free(msg);
}
else
yyerror ("parse error; also virtual memory exceeded");
}
else
#endif /* YYERROR_VERBOSE */
yyerror("parse error");
}
goto yyerrlab1;
yyerrlab1: /* here on error raised explicitly by an action */
if (yyerrstatus == 3)
{
/* if just tried and failed to reuse lookahead token after an
error, discard it. */
/* return failure if at end of input */
if (yychar == YYEOF)
YYABORT;
#if YYDEBUG != 0
if (yydebug)
fprintf(stderr, "Discarding token %d (%s).\n", yychar, yytname
[yychar1]);
#endif
yychar = YYEMPTY;
}
/* Else will try to reuse lookahead token
after shifting the error token. */
yyerrstatus = 3; /* Each real token shifted decrements
this */
goto yyerrhandle;
yyerrdefault: /* current state does not do anything special for the
error token. */
#if 0
/* This is wrong; only states that explicitly want error tokens
should shift them. */
yyn = yydefact[yystate]; /* If its default is to accept any token,
ok. Otherwise pop it.*/
if (yyn) goto yydefault;
#endif
yyerrpop: /* pop the current state because it cannot handle the
error token */
if (yyssp == yyss) YYABORT;
yyvsp--;
yystate = *--yyssp;
#ifdef YYLSP_NEEDED
yylsp--;
#endif
#if YYDEBUG != 0
if (yydebug)
{
short *ssp1 = yyss - 1;
fprintf (stderr, "Error: state stack now");
while (ssp1 != yyssp)
fprintf (stderr, " %d", *++ssp1);
fprintf (stderr, "\n");
}
#endif
yyerrhandle:
yyn = yypact[yystate];
if (yyn == YYFLAG)
goto yyerrdefault;
yyn += YYTERROR;
if (yyn < 0 || yyn > YYLAST || yycheck[yyn] != YYTERROR)
goto yyerrdefault;
yyn = yytable[yyn];
if (yyn < 0)
{
if (yyn == YYFLAG)
goto yyerrpop;
yyn = -yyn;
goto yyreduce;
}
else if (yyn == 0)
goto yyerrpop;
if (yyn == YYFINAL)
YYACCEPT;
#if YYDEBUG != 0
if (yydebug)
fprintf(stderr, "Shifting error token, ");
#endif
*++yyvsp = yylval;
#ifdef YYLSP_NEEDED
*++yylsp = yylloc;
#endif
yystate = yyn;
goto yynewstate;
}
#line 27 "ddd.y"
yylex() {
int c;
c = getchar();
if ( isdigit( c ) ) {
yylval = c - '0';
return NUMBER;
}
return( c );
}
void main() {
yyparse();
}
yyerror ( char *s ) /* Called by yyparse on error */
{
printf ("%s\n", s);
}
--- cut here ---------------------------------------------------------
----------------------------------------------------------------------
