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

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