+For this parser we do not have a separate action table. The action
+table normally maps terminals to one of the actions SHIFT, REDUCE(p), or
+ACCEPT. We can find which terminals to SHIFT via a lookup in the go to
+table, and most states have at most one reducible production and in that
+case to effect that reduction for any non-shiftable terminal in the
+look-ahead.
+
+However, with SLR, LALR, and canonical-LR grammars, there may
+occasionally be multiple possible reductions which we choose between
+based on the look-ahead. To handle this possibility we allow reductions
+to be stored in the go to table. An extra flag indicates if an entry is
+a state to go to, or a production to reduce. We add the entries with
+that flag here, if necessary.
+
+###### functions
+ #define IS_REDUCTION (0x8000)
+
+ static void gen_action(FILE *f, struct grammar *g)
+ {
+ int i, j, k;
+ for (i = 0; i < g->states; i++) {
+ struct itemset *is = g->statetab[i];
+ struct symset *gt = &is->go_to;
+
+ if (is->reducible_prod != MANY_REDUCIBLE)
+ continue;
+ for (j = 0; j < is->items.cnt; j++) {
+ int itm = is->items.syms[j];
+ int p = item_prod(itm);
+ int bp = item_dot(itm);
+ struct production *pr = g->productions[p];
+ struct symset la;
+ if (bp != pr->body_size)
+ continue;
+ /* This is a reducible item */
+ if (g->follow)
+ la = g->follow[pr->head->num];
+ else
+ la = set_find(g, is->items.data[j]);
+ for (k = 0 ; k < la.cnt; k++)
+ symset_add(gt, la.syms[k], p | IS_REDUCTION);
+ }
+ }
+ }
+
+### States, reductions, and the go to tables.
+
+For each state we record the go to table and the reducible production if
+there is one, the details of which are in a separate table of
+reductions. Some of the details of the reducible production are stored
+in the `do_reduce` function to come later. In the go to table we store
+the production number and in the reductions table: the body size (useful
+for stack management), the resulting symbol (useful for knowing how to
+free data later), and the size of the resulting asn object (useful for
+preallocation space.
code / ocean / blobdiff