Non puoi selezionare più di 25 argomenti
Gli argomenti devono iniziare con una lettera o un numero, possono includere trattini ('-') e possono essere lunghi fino a 35 caratteri.
122 righe
2.3 KiB
122 righe
2.3 KiB
%{
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/* compile: leg -o calc.c calc.leg
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* cc -o calc calc.c
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*
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* run: echo "2+3" | ./calc
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*/
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#define NSYMBOLS 256
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union u_t {
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int ival;
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char *sval;
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};
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typedef struct symbol_t {
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char *ident;
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int value;
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} symbol_t;
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typedef struct table_t {
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symbol_t *array[NSYMBOLS];
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int size;
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} table_t;
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#define YYSTYPE union u_t
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YYSTYPE yylval;
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table_t table;
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// This buffer is for storing yytext identifier during assignement
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char *ident_buf;
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symbol_t* new_symbol(char *ident, int value)
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{
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symbol_t* s = malloc(sizeof(symbol_t));
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char * ident_copy = malloc(strlen(ident) + 1);
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strcpy(ident_copy, ident);
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free(ident_buf);
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s->ident = ident_copy;
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s->value = value;
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return s;
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}
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symbol_t * add(char *ident, int value)
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{
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symbol_t *new_s = new_symbol(ident, value);
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if (table.size >= NSYMBOLS) {
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printf("Error: too many symbols\n");
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exit(1);
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}
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int i = table.size;
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table.array[i] = new_s;
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table.size++;
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return table.array[i];
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}
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// Returns int value of identifier, when identifier is undefined, returns 0
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int get_value(const char *ident)
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{
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for(int i=0; i < table.size; i++) {
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//printf("comparaison %s, %s\n", table.array[i].ident, ident);
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if (strcmp(table.array[i]->ident, ident) == 0) {
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return table.array[i]->value;
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}
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}
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// printf("'%s' identifier not found\n", ident);
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return 0;
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}
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%}
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start = e:exp { yylval = e }
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exp = - (a:assign { $$ = a }
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| s:sum { $$ = s }
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)
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assign = l:IDENT { ident_buf = strdup(l.sval) }
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EQUAL n:sum { $$.ival = add(ident_buf, n.ival)->value;}
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sum = PLUS* l:prod
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( PLUS+ r:prod { l.ival += r.ival }
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| MINUS r:prod { l.ival -= r.ival }
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)* { $$.ival = l.ival }
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prod = l:neg
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( MULTI r:neg { l.ival *= r.ival }
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| DIVIDE r:neg { l.ival /= r.ival }
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| MODULO r:neg { l.ival %= r.ival }
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)* { $$.ival = l.ival }
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neg = MINUS n:neg { $$.ival = -n.ival }
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| n:value { $$.ival = n.ival }
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value = n:NUMBER { $$.ival = n.ival }
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| l:IDENT { $$.ival = get_value(l.sval) }
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- = [ \t]*
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NUMBER = < [0-9]+ > - { $$.ival = atoi(yytext) }
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PLUS = '+' -
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MINUS = '-' -
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MULTI = '*' -
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DIVIDE = '/' -
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MODULO = '%' -
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EQUAL = '=' -
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IDENT = < [a-zA-Z]+ > - { $$.sval = yytext }
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%%
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int main(int argc, char **argv)
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{
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while (yyparse()) {
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printf("%d\n", yylval.ival);
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}
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return 0;
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}
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