external/bsd/byacc/dist/test/calc.y

   1 /*      $NetBSD: calc.y,v 1.1.1.5 2013/04/06 14:45:27 christos Exp $    */
   2
   3 %{
   4 # include <stdio.h>
   5 # include <ctype.h>
   6
   7 int regs[26];
   8 int base;
   9
  10 extern int yylex(void);
  11 static void yyerror(const char *s);
  12
  13 %}
  14
  15 %start list
  16
  17 %token DIGIT LETTER
  18
  19 %left '|'
  20 %left '&'
  21 %left '+' '-'
  22 %left '*' '/' '%'
  23 %left UMINUS   /* supplies precedence for unary minus */
  24
  25 %% /* beginning of rules section */
  26
  27 list  :  /* empty */
  28       |  list stat '\n'
  29       |  list error '\n'
  30             {  yyerrok ; }
  31       ;
  32
  33 stat  :  expr
  34             {  printf("%d\n",$1);}
  35       |  LETTER '=' expr
  36             {  regs[$1] = $3; }
  37       ;
  38
  39 expr  :  '(' expr ')'
  40             {  $$ = $2; }
  41       |  expr '+' expr
  42             {  $$ = $1 + $3; }
  43       |  expr '-' expr
  44             {  $$ = $1 - $3; }
  45       |  expr '*' expr
  46             {  $$ = $1 * $3; }
  47       |  expr '/' expr
  48             {  $$ = $1 / $3; }
  49       |  expr '%' expr
  50             {  $$ = $1 % $3; }
  51       |  expr '&' expr
  52             {  $$ = $1 & $3; }
  53       |  expr '|' expr
  54             {  $$ = $1 | $3; }
  55       |  '-' expr %prec UMINUS
  56             {  $$ = - $2; }
  57       |  LETTER
  58             {  $$ = regs[$1]; }
  59       |  number
  60       ;
  61
  62 number:  DIGIT
  63          {  $$ = $1; base = ($1==0) ? 8 : 10; }
  64       |  number DIGIT
  65          {  $$ = base * $1 + $2; }
  66       ;
  67
  68 %% /* start of programs */
  69
  70 int
  71 main (void)
  72 {
  73     while(!feof(stdin)) {
  74         yyparse();
  75     }
  76     return 0;
  77 }
  78
  79 static void
  80 yyerror(const char *s)
  81 {
  82     fprintf(stderr, "%s\n", s);
  83 }
  84
  85 int
  86 yylex(void)
  87 {
  88         /* lexical analysis routine */
  89         /* returns LETTER for a lower case letter, yylval = 0 through 25 */
  90         /* return DIGIT for a digit, yylval = 0 through 9 */
  91         /* all other characters are returned immediately */
  92
  93     int c;
  94
  95     while( (c=getchar()) == ' ' )   { /* skip blanks */ }
  96
  97     /* c is now nonblank */
  98
  99     if( islower( c )) {
 100         yylval = c - 'a';
 101         return ( LETTER );
 102     }
 103     if( isdigit( c )) {
 104         yylval = c - '0';
 105         return ( DIGIT );
 106     }
 107     return( c );
 108 }