static Renode *parseatom(struct cstate *g)
{
	Renode *atom;
	if (g->lookahead == L_CHAR) {
		atom = newnode(g, P_CHAR);
		atom->c = g->yychar;
		next(g);
		return atom;
	}
	if (g->lookahead == L_CCLASS) {
		atom = newnode(g, P_CCLASS);
		atom->cc = g->yycc;
		next(g);
		return atom;
	}
	if (g->lookahead == L_NCCLASS) {
		atom = newnode(g, P_NCCLASS);
		atom->cc = g->yycc;
		next(g);
		return atom;
	}
	if (g->lookahead == L_REF) {
		atom = newnode(g, P_REF);
		if (g->yychar == 0 || g->yychar >= g->nsub || !g->sub[g->yychar])
			die(g, "invalid back-reference");
		atom->n = g->yychar;
		atom->x = g->sub[g->yychar];
		next(g);
		return atom;
	}
	if (accept(g, '.'))
		return newnode(g, P_ANY);
	if (accept(g, '(')) {
		atom = newnode(g, P_PAR);
		if (g->nsub == REG_MAXSUB)
			die(g, "too many captures");
		atom->n = g->nsub++;
		atom->x = parsealt(g);
		g->sub[atom->n] = atom;
		if (!accept(g, ')'))
			die(g, "unmatched '('");
		return atom;
	}
	if (accept(g, L_NC)) {
		atom = parsealt(g);
		if (!accept(g, ')'))
			die(g, "unmatched '('");
		return atom;
	}
	if (accept(g, L_PLA)) {
		atom = newnode(g, P_PLA);
		atom->x = parsealt(g);
		if (!accept(g, ')'))
			die(g, "unmatched '('");
		return atom;
	}
	if (accept(g, L_NLA)) {
		atom = newnode(g, P_NLA);
		atom->x = parsealt(g);
		if (!accept(g, ')'))
			die(g, "unmatched '('");
		return atom;
	}
	die(g, "syntax error");
	return NULL;
}
static Renode *parseatom(struct cstate *g)
{
	Renode *atom;
	if (g->lookahead == L_CHAR) {
		atom = newnode(g, P_CHAR);
		atom->c = g->yychar;
		next(g);
		return atom;
	}
	if (g->lookahead == L_CCLASS) {
		atom = newnode(g, P_CCLASS);
		atom->cc = g->yycc;
		next(g);
		return atom;
	}
	if (g->lookahead == L_NCCLASS) {
		atom = newnode(g, P_NCCLASS);
		atom->cc = g->yycc;
		next(g);
		return atom;
	}
	if (g->lookahead == L_REF) {
		atom = newnode(g, P_REF);
		if (g->yychar == 0 || g->yychar >= g->nsub || !g->sub[g->yychar])
			die(g, "invalid back-reference");
		atom->n = g->yychar;
		atom->x = g->sub[g->yychar];
		next(g);
		return atom;
	}
	if (accept(g, '.'))
		return newnode(g, P_ANY);
	if (accept(g, '(')) {
		atom = newnode(g, P_PAR);
		if (g->nsub == REG_MAXSUB)
			die(g, "too many captures");
		atom->n = g->nsub++;
		atom->x = parsealt(g);
		g->sub[atom->n] = atom;
		if (!accept(g, ')'))
			die(g, "unmatched '('");
		return atom;
	}
	if (accept(g, L_NC)) {
		atom = parsealt(g);
		if (!accept(g, ')'))
			die(g, "unmatched '('");
		return atom;
	}
	if (accept(g, L_PLA)) {
		atom = newnode(g, P_PLA);
		atom->x = parsealt(g);
		if (!accept(g, ')'))
			die(g, "unmatched '('");
		return atom;
	}
	if (accept(g, L_NLA)) {
		atom = newnode(g, P_NLA);
		atom->x = parsealt(g);
		if (!accept(g, ')'))
			die(g, "unmatched '('");
		return atom;
	}
	die(g, "syntax error");
	return NULL;
}