calc.y revision 1.1.1.4 
1/*	$NetBSD: calc.y,v 1.1.1.4 2011/09/10 21:22:08 christos Exp $	*/
2
3%{
4# include <stdio.h>
5# include <ctype.h>
6
7int regs[26];
8int 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
24list  :  /* empty */
25      |  list stat '\n'
26      |  list error '\n'
27            {  yyerrok ; }
28      ;
29
30stat  :  expr
31            {  printf("%d\n",$1);}
32      |  LETTER '=' expr
33            {  regs[$1] = $3; }
34      ;
35
36expr  :  '(' 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
59number:  DIGIT
60         {  $$ = $1; base = ($1==0) ? 8 : 10; }
61      |  number DIGIT
62         {  $$ = base * $1 + $2; }
63      ;
64
65%% /* start of programs */
66
67#ifdef YYBYACC
68extern int YYLEX_DECL();
69static void YYERROR_DECL();
70#endif
71
72int
73main (void)
74{
75    while(!feof(stdin)) {
76	yyparse();
77    }
78    return 0;
79}
80
81static void
82yyerror(const char *s)
83{
84    fprintf(stderr, "%s\n", s);
85}
86
87int
88yylex(void)
89{
90	/* lexical analysis routine */
91	/* returns LETTER for a lower case letter, yylval = 0 through 25 */
92	/* return DIGIT for a digit, yylval = 0 through 9 */
93	/* all other characters are returned immediately */
94
95    int c;
96
97    while( (c=getchar()) == ' ' )   { /* skip blanks */ }
98
99    /* c is now nonblank */
100
101    if( islower( c )) {
102	yylval = c - 'a';
103	return ( LETTER );
104    }
105    if( isdigit( c )) {
106	yylval = c - '0';
107	return ( DIGIT );
108    }
109    return( c );
110}
111