dsl_arithmetic_5_dependencies.h

template<typename Tag>
std::set<id> join_sets(op<Tag, std::set<id>> const& op)
{
   std::set<id> out;
   for (auto r: op.rands())
      out.insert(r.begin(), r.end());
   return out;
}

std::set<id> dependencies_alg(expression_r<std::set<id>> const& e)
{
   if (auto* o = get_as_add(e)) return join_sets(*o);
   if (auto* o = get_as_mul(e)) return join_sets(*o);
   if (auto* v = get_as_var(e)) return {*v};
   return {};
}

std::set<id> dependencies(expression const& e)
{
   return cata<std::set<id>>(dependencies_alg, e);
}