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