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

   1 /*      $NetBSD: code_calc.y,v 1.1.1.4 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 #ifdef YYBISON
  11 int yylex(void);
  12 static void yyerror(const char *s);
  13 #endif
  14
  15 %}
  16
  17 %start list
  18
  19 %token DIGIT LETTER
  20
  21 %left '|'
  22 %left '&'
  23 %left '+' '-'
  24 %left '*' '/' '%'
  25 %left UMINUS   /* supplies precedence for unary minus */
  26
  27 %% /* beginning of rules section */
  28
  29 list  :  /* empty */
  30       |  list stat '\n'
  31       |  list error '\n'
  32             {  yyerrok ; }
  33       ;
  34
  35 stat  :  expr
  36             {  printf("%d\n",$1);}
  37       |  LETTER '=' expr
  38             {  regs[$1] = $3; }
  39       ;
  40
  41 expr  :  '(' expr ')'
  42             {  $$ = $2; }
  43       |  expr '+' expr
  44             {  $$ = $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             {  $$ = $1 & $3; }
  55       |  expr '|' expr
  56             {  $$ = $1 | $3; }
  57       |  '-' expr %prec UMINUS
  58             {  $$ = - $2; }
  59       |  LETTER
  60             {  $$ = regs[$1]; }
  61       |  number
  62       ;
  63
  64 number:  DIGIT
  65          {  $$ = $1; base = ($1==0) ? 8 : 10; }
  66       |  number DIGIT
  67          {  $$ = base * $1 + $2; }
  68       ;
  69
  70 %% /* start of programs */
  71
  72 #ifdef YYBYACC
  73 extern int YYLEX_DECL();
  74 #endif
  75
  76 int
  77 main (void)
  78 {
  79     while(!feof(stdin)) {
  80         yyparse();
  81     }
  82     return 0;
  83 }
  84
  85 static void
  86 yyerror(const char *s)
  87 {
  88     fprintf(stderr, "%s\n", s);
  89 }
  90
  91 int
  92 yylex(void)
  93 {
  94         /* lexical analysis routine */
  95         /* returns LETTER for a lower case letter, yylval = 0 through 25 */
  96         /* return DIGIT for a digit, yylval = 0 through 9 */
  97         /* all other characters are returned immediately */
  98
  99     int c;
 100
 101     while( (c=getchar()) == ' ' )   { /* skip blanks */ }
 102
 103     /* c is now nonblank */
 104
 105     if( islower( c )) {
 106         yylval = c - 'a';
 107         return ( LETTER );
 108     }
 109     if( isdigit( c )) {
 110         yylval = c - '0';
 111         return ( DIGIT );
 112     }
 113     return( c );
 114 }