1/*	$NetBSD: calc_code_requires.y,v 1.1.1.1 2021/02/20 20:30:07 christos Exp $	*/
2
3%code requires { /* CODE-REQUIRES */ }
4%code requires { /* CODE-REQUIRES2 */ }
5
6%{
7# include <stdio.h>
8# include <ctype.h>
9
10int regs[26];
11int base;
12
13extern int yylex(void);
14static void yyerror(const char *s);
15
16%}
17
18%start list
19
20%token DIGIT LETTER
21
22%left '|'
23%left '&'
24%left '+' '-'
25%left '*' '/' '%'
26%left UMINUS   /* supplies precedence for unary minus */
27
28%% /* beginning of rules section */
29
30list  :  /* empty */
31      |  list stat '\n'
32      |  list error '\n'
33            {  yyerrok ; }
34      ;
35
36stat  :  expr
37            {  printf("%d\n",$1);}
38      |  LETTER '=' expr
39            {  regs[$1] = $3; }
40      ;
41
42expr  :  '(' expr ')'
43            {  $$ = $2; }
44      |  expr '+' expr
45            {  $$ = $1 + $3; }
46      |  expr '-' expr
47            {  $$ = $1 - $3; }
48      |  expr '*' expr
49            {  $$ = $1 * $3; }
50      |  expr '/' expr
51            {  $$ = $1 / $3; }
52      |  expr '%' expr
53            {  $$ = $1 % $3; }
54      |  expr '&' expr
55            {  $$ = $1 & $3; }
56      |  expr '|' expr
57            {  $$ = $1 | $3; }
58      |  '-' expr %prec UMINUS
59            {  $$ = - $2; }
60      |  LETTER
61            {  $$ = regs[$1]; }
62      |  number
63      ;
64
65number:  DIGIT
66         {  $$ = $1; base = ($1==0) ? 8 : 10; }
67      |  number DIGIT
68         {  $$ = base * $1 + $2; }
69      ;
70
71%% /* start of programs */
72
73int
74main (void)
75{
76    while(!feof(stdin)) {
77	yyparse();
78    }
79    return 0;
80}
81
82static void
83yyerror(const char *s)
84{
85    fprintf(stderr, "%s\n", s);
86}
87
88int
89yylex(void)
90{
91	/* lexical analysis routine */
92	/* returns LETTER for a lower case letter, yylval = 0 through 25 */
93	/* return DIGIT for a digit, yylval = 0 through 9 */
94	/* all other characters are returned immediately */
95
96    int c;
97
98    while( (c=getchar()) == ' ' )   { /* skip blanks */ }
99
100    /* c is now nonblank */
101
102    if( islower( c )) {
103	yylval = c - 'a';
104	return ( LETTER );
105    }
106    if( isdigit( c )) {
107	yylval = c - '0';
108	return ( DIGIT );
109    }
110    return( c );
111}
112