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3.1 hoc1

3.1.1 makefile

 hoc1: hoc.o
  cc hoc.o -o hoc1

3.1.2 hoc.y

 %{
 #define YYSTYPE double /* data type of yacc stack */
 %}
 %token NUMBER
 %left '+' /* left associative, same precedence */
 %left '*' '/' /* left assoc., higher precedence */
 %%
 list : /* nothing */
  | list '\n'
  | list expr '\n' { printf("\t%.8g\n", $2); }
  ;
 expr: NUMBER { $$ = $1; }
  | expr '+' expr { $$ = $1 + $3; }
  | expr '-' expr { $$ = $1 - $3; }
  | expr '*' expr { $$ = $1 * $3; }
  | expr '/' expr { $$ = $1 / $3; }
  | '(' expr ')' { $$ = $2; }
  ;
 %%
 /* end of grammar */

 #include <stdio.h>
 #include <ctype.h>
 char *progname; /* for error messages */
 int lineno = 1;

 main(argc, argv) /* hoc1 */
  char *argv[];
 {
  progname = argv[0];
  yyparse;
 }

 yylex /* hoc1 */
 {
  int c;

  while ((c=getchar) == ' ' || c == '\t')
  ;
  if (c == EOF)
  return 0;
  if (c == '.' || isdigit(c)) { /* number */
  ungetc(c, stdin);
  scanf("%lf", &yylval);
  return NUMBER;
  if (c == '\n')
  lineno++;
  return c;
 }

 yyerror(s) /* called for yacc syntax error */
  char *s;
 {
  warning(s, (char*)0);
 }

 warning(s, t) /* print warning message */
  char *s, *t;
 {
  fprintf(stderr, "%s: %s", progname, s);
  if (t)
  fprintf(stderr, " %s", t);
  fprintf(stderr, " near line %d\n", lineno);
 }

3.1.3 hoc1.y , версия 1.5

 %{
 #define YYSTYPE double /* data type of yacc stack */
 %}
 %token NUMBER
 %left '-' '+'
 %left '*' '/'
 %left UNARYMINUS
 %%

 list: /* nothing */
  | list '\n'
  | list expr '\n' { printf("\t%.8g\n", $2); }
  ;
 expr: NUMBER { $$ = $1; }
  | expr '+' expr { $$ = $1 + $3; }
  | expr '-' expr { $$ = $1 - $3; }
  | expr '*' expr { $$ = $1 * $3; }
  | expr '/' expr { $$ = $1 / $3; }
  | '-' expr %prec UNARYMINUS { $$ = -$2; } /* new */
  | '(' expr ')' { $$ = $2; }
  ;
 %%
 /* end of grammar */

 #include <stdio.h>
 #include <ctype.h>
 char *progname; /* for error messages */
 int lineno = 1;

 main(argc, argv) /* hoc1 */
  char *argv[];
 {
  progname = argv[0];
  yyparse;
 }

 yylex /* hoc1 */
 {
  int c;

  while ((c=getchar) == ' ' || с == '\t')
  ;
  if (c == EOF)
  return 0;
  if (c == '.' || isdigit(c)) { /* number */
  ungetc(c, stdin);
  scanf("%lf", &yylval);
  return NUMBER;