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|
%{
# include <stdio.h>
# include <ctype.h>
int regs[26];
int base;
%}
%start list
%token DIGIT LETTER
%left '|'
%left '&'
%left '+' '-'
%left '*' '/' '%'
%left UMINUS /* supplies precedence for unary minus */
%% /* beginning of rules section */
list : /* empty */
| list stat '\n'
| list error '\n'
{ yyerrok ; }
;
stat : expr
{ printf("%d\n",$1);}
| LETTER '=' expr
{ regs[$1] = $3; }
;
expr : '(' expr ')'
{ $$ = $2; }
| expr '+' expr
{ $$ = $1 + $3; }
| expr '-' expr
{ $$ = $1 - $3; }
| expr '*' expr
{ $$ = $1 * $3; }
| expr '/' expr
{ $$ = $1 / $3; }
| expr '%' expr
{ $$ = $1 % $3; }
| expr '&' expr
{ $$ = $1 & $3; }
| expr '|' expr
{ $$ = $1 | $3; }
| '-' expr %prec UMINUS
{ $$ = - $2; }
| LETTER
{ $$ = regs[$1]; }
| number
;
number: DIGIT
{ $$ = $1; base = ($1==0) ? 8 : 10; }
| number DIGIT
{ $$ = base * $1 + $2; }
;
%% /* start of programs */
int
main (void)
{
while(!feof(stdin)) {
yyparse();
}
return 0;
}
static void
yyerror(const char *s)
{
fprintf(stderr, "%s\n", s);
}
int
yylex(void)
{
/* lexical analysis routine */
/* returns LETTER for a lower case letter, yylval = 0 through 25 */
/* return DIGIT for a digit, yylval = 0 through 9 */
/* all other characters are returned immediately */
int c;
while( (c=getchar()) == ' ' ) { /* skip blanks */ }
/* c is now nonblank */
if( islower( c )) {
yylval = c - 'a';
return ( LETTER );
}
if( isdigit( c )) {
yylval = c - '0';
return ( DIGIT );
}
return( c );
}
|
