countery.c

使用LEX/YACC 编写的计算器程序 在VC环境下使用

		 &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 3:
#line 24 "countery.y"
{ yyvsp[-2].symp->value = yyvsp[0].dval; ;
    break;}
case 4:
#line 25 "countery.y"
{ printf("= %g\n", yyvsp[0].dval); ;
    break;}
case 5:
#line 28 "countery.y"
{ yyval.dval = yyvsp[-2].dval + yyvsp[0].dval; ;
    break;}
case 6:
#line 29 "countery.y"
{ yyval.dval = yyvsp[-2].dval - yyvsp[0].dval; ;
    break;}
case 7:
#line 30 "countery.y"
{ yyval.dval = yyvsp[-2].dval * yyvsp[0].dval; ;
    break;}
case 8:
#line 32 "countery.y"
{
				if(yyvsp[0].dval == 0.0)
					yyerror("divide by zero");
				else
					yyval.dval = yyvsp[-2].dval / yyvsp[0].dval;
			;
    break;}
case 9:
#line 38 "countery.y"
{ yyval.dval = -yyvsp[0].dval; ;
    break;}
case 10:
#line 39 "countery.y"
{ yyval.dval = yyvsp[-1].dval; ;
    break;}
case 12:
#line 41 "countery.y"
{ yyval.dval = yyvsp[0].symp->value; ;
    break;}
case 13:
#line 43 "countery.y"
{
				if(yyvsp[-3].symp->funcptr)
					yyval.dval = (yyvsp[-3].symp->funcptr)(yyvsp[-1].dval);
				else
				{
					printf("%s not a function\n", yyvsp[-3].symp->name);
					yyval.dval = 0.0;
				}
			;
    break;}
}
   /* the action file gets copied in in place of this dollarsign */
#line 509 "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 53 "countery.y"


/*function*/
struct symtab *
symlook(s)
char *s;
{
	char *p;
	struct symtab *sp;
	
	for(sp = symtab; sp < &symtab[NSYMS]; sp++)
	{
		if(sp->name && !strcmp(sp->name, s))
			return sp;
		if(!sp->name)
		{
			sp->name = strdup(s);
			return sp;
		}
	}
	yyerror("Too many symbols");
	exit(1);
}

addfunc(name, func)
char *name;
double (*func)();
{
	struct symtab *sp = symlook(name);
	sp->funcptr = func;
}

main()
{
	extern double sqrt(), exp(), log();
	
	addfunc("sqrt", sqrt);
	addfunc("exp", exp);
	addfunc("log", log);
	yyparse();
}