+ if (e.info(info_flags::relation_equal)) {
+
+ // Argument is a relation: convert it to a map
+ exmap m;
+ const ex & s = e.op(0);
+ m.insert(std::make_pair(s, e.op(1)));
+
+ if (is_exactly_a<mul>(s) || is_exactly_a<power>(s))
+ options |= subs_options::pattern_is_product;
+ else
+ options |= subs_options::pattern_is_not_product;
+
+ return bp->subs(m, options);
+
+ } else if (e.info(info_flags::list)) {
+
+ // Argument is a list: convert it to a map
+ exmap m;
+ GINAC_ASSERT(is_a<lst>(e));
+ for (lst::const_iterator it = ex_to<lst>(e).begin(); it != ex_to<lst>(e).end(); ++it) {
+ ex r = *it;
+ if (!r.info(info_flags::relation_equal))
+ throw(std::invalid_argument("basic::subs(ex): argument must be a list of equations"));
+ const ex & s = r.op(0);
+ m.insert(std::make_pair(s, r.op(1)));
+
+ // Search for products and powers in the expressions to be substituted
+ // (for an optimization in expairseq::subs())
+ if (is_exactly_a<mul>(s) || is_exactly_a<power>(s))
+ options |= subs_options::pattern_is_product;
+ }
+ if (!(options & subs_options::pattern_is_product))
+ options |= subs_options::pattern_is_not_product;
+
+ return bp->subs(m, options);
+
+ } else
+ throw(std::invalid_argument("ex::subs(ex): argument must be a relation_equal or a list"));
+}
+
+/** Traverse expression tree with given visitor, preorder traversal. */
+void ex::traverse_preorder(visitor & v) const
+{
+ accept(v);
+
+ size_t n = nops();
+ for (size_t i = 0; i < n; ++i)
+ op(i).traverse_preorder(v);
+}
+
+/** Traverse expression tree with given visitor, postorder traversal. */
+void ex::traverse_postorder(visitor & v) const
+{
+ size_t n = nops();
+ for (size_t i = 0; i < n; ++i)
+ op(i).traverse_postorder(v);
+
+ accept(v);