+ if (shift(&p, tk->num, tk, states)) {
+ if (tk->num == TK_out)
+ p.ignored_indents >>= 1;
+ if (tk->num == TK_in)
+ p.ignored_indents <<= 1;
+
+ parser_trace_action(trace, "Shift");
+ tk = NULL;
+ ## did shift
+ continue;
+ } else if (tk->num == TK_newline &&
+ shift(&p, p.tk_eol, tk, states)) {
+ tk = tok_copy(*tk);
+ parser_trace_action(trace, "ShiftEOL");
+ continue;
+ }
+
+ if (tk->num == TK_in) {
+ int should_reduce;
+ if (states[tos->state].reduce_prod == MANY_REDUCIBLE)
+ /* Only reduce if TK_in in lookahead */
+ should_reduce = (search(&states[tos->state], TK_in, 1) >= 0);
+ else
+ /* Only reduce if we cannot shift anything */
+ should_reduce = (states[tos->state].go_to_cnt == 0);
+ if (!should_reduce) {
+ /* No indent expected here and reduce is not indicated,
+ * so ignore IN
+ */
+ free(tk);
+ tk = NULL;
+ p.ignored_indents <<= 1;
+ p.ignored_indents |= 1;
+ parser_trace_action(trace, "Ignore");
+ continue;
+ }
+ }
+
+We have already discussed the bulk of the handling of a "reduce" action,
+with the `pop()` and `shift()` functions doing much of the work. There
+is a little more complexity needed to manage storage for the asn (Abstract
+Syntax Node), and also a test of whether the reduction is permitted.
+
+When we try to shift the result of reducing production-zero, it will
+fail because there is no next state. In this case the asn will not have
+been stored on the stack, so it get stored in the `ret` variable, and we
+report that that input has been accepted.
+
+###### parser vars
+
+ void *ret = NULL;
+ int reduction;
+
+###### try reduce
+
+ reduction = states[tos->state].reduce_prod;
+ if (reduction == MANY_REDUCIBLE)
+ reduction = search(&states[tos->state], tk->num, 1);
+ if (reduction >= 0) {
+ void **body;
+ void *res;
+ int size = reductions[reduction].size;
+ int res_size = reductions[reduction].result_size;
+
+ body = p.asn_stack + (p.tos - size);
+ res = res_size ? calloc(1, res_size) : NULL;
+ res_size = do_reduce(reduction, body, config, res);
+ if (res_size != reductions[reduction].result_size)
+ abort();
+ pop(&p, size, do_free);
+ if (!shift(&p, reductions[reduction].sym, res, states)) {
+ accepted = 1;
+ ret = res;
+ parser_trace_action(trace, "Accept");
+ } else
+ parser_trace_action(trace, "Reduce");
+ continue;
+ }
code / ocean / blobdiff