2.9BSD - /usr/src/cmd/m4/m4y.y

   1: %{
   2: extern long evalval;
   3: #define YYSTYPE long
   4: %}
   5: 
   6: %term DIGITS
   7: %left '|'
   8: %left '&'
   9: %right '!'
  10: %nonassoc GT GE LT LE NE EQ
  11: %left '+' '-'
  12: %left '*' '/' '%'
  13: %right POWER
  14: %right UMINUS
  15: %%
  16: 
  17: s   : e ={ evalval = $1; }
  18:     |   ={ evalval = 0; }
  19:     ;
  20: 
  21: e   : e '|' e   ={ $$ = ($1!=0 || $3!=0) ? 1 : 0; }
  22:     | e '&' e   ={ $$ = ($1!=0 && $3!=0) ? 1 : 0; }
  23:     | '!' e     ={ $$ = $2 == 0; }
  24:     | e EQ e    ={ $$ = $1 == $3; }
  25:     | e NE e    ={ $$ = $1 != $3; }
  26:     | e GT e    ={ $$ = $1 > $3; }
  27:     | e GE e    ={ $$ = $1 >= $3; }
  28:     | e LT e    ={ $$ = $1 < $3; }
  29:     | e LE e    ={ $$ = $1 <= $3; }
  30:     | e '+' e   ={ $$ = ($1+$3); }
  31:     | e '-' e   ={ $$ = ($1-$3); }
  32:     | e '*' e   ={ $$ = ($1*$3); }
  33:     | e '/' e   ={ $$ = ($1/$3); }
  34:     | e '%' e   ={ $$ = ($1%$3); }
  35:     | '(' e ')' ={ $$ = ($2); }
  36:     | e POWER e ={ for ($$=1; $3-->0; $$ *= $1); }
  37:     | '-' e %prec UMINUS    ={ $$ = $2-1; $$ = -$2; }
  38:     | '+' e %prec UMINUS    ={ $$ = $2-1; $$ = $2; }
  39:     | DIGITS    ={ $$ = evalval; }
  40:     ;
  41: 
  42: %%
  43: 
  44: yylex() {
  45:     extern char *pe;
  46: 
  47:     while (*pe==' ' || *pe=='\t' || *pe=='\n')
  48:         pe++;
  49:     switch(*pe) {
  50:     case '\0':
  51:     case '+':
  52:     case '-':
  53:     case '/':
  54:     case '%':
  55:     case '(':
  56:     case ')':
  57:         return(*pe++);
  58:     case '^':
  59:         pe++;
  60:         return(POWER);
  61:     case '*':
  62:         return(peek('*', POWER, '*'));
  63:     case '>':
  64:         return(peek('=', GE, GT));
  65:     case '<':
  66:         return(peek('=', LE, LT));
  67:     case '=':
  68:         return(peek('=', EQ, EQ));
  69:     case '|':
  70:         return(peek('|', '|', '|'));
  71:     case '&':
  72:         return(peek('&', '&', '&'));
  73:     case '!':
  74:         return(peek('=', NE, '!'));
  75:     default:
  76:         evalval = 0;
  77:         while (*pe >= '0' && *pe <= '9')
  78:             evalval = evalval*10 + *pe++ - '0';
  79:         return(DIGITS);
  80:     }
  81: }
  82: 
  83: peek(c, r1, r2)
  84: {
  85:     if (*++pe != c)
  86:         return(r2);
  87:     ++pe;
  88:     return(r1);
  89: }
  90: 
  91: yyerror(s)
  92: char *s;
  93: {
  94: }

Defined functions

Defined macros