Hi All, I have an accumulator (a) that takes an initial value (x_), and another (b), whose initial value (x_) depends on that of (a). I would have thought that this is feasible because accumulator_set initializes (a) before (b), but apparently b.x_ is initialized with a garbage value. namespace impl { template class accu_a_impl : public accumulator_base { public: typedef Sample result_type; template<typename Args> accu_a_impl(Args const &args) :x_( args[kwd<Id>::value] ) { } result_type result(dont_care) const { return x_; } private: result_type x_; }; } namespace tag { template <typename Id = mpl::void_> struct accu_a : depends_on<> { typedef accumulators::impl::accu_a_implmpl::_1,Id impl; }; } namespace impl { template class accu_b_impl : public accumulator_base { typedef tag::accu_a<Id1> a_type; public: typedef Sample result_type; template<typename Args> accu_b_impl(Args const &args) :x_( extract_result(args[accumulator]) // faulty? ) { } template<typename Args> void operator ()(Args const &args) { // overrides initialization for the sake of testing x_ = extract_result(args[accumulator]); } private: result_type x_; }; } namespace tag { template struct accu_b : depends_on { typedef accumulators::impl::accu_b_implmpl::_1,Id0,Id1 impl; }; } *.cpp typedef mpl::size_t<0> id0; typedef mpl::size_t<1> id1; typedef double value_type; typedef tag::accu_a<id0> a_type; typedef tag::accu_b b_type; typedef accumulator_set< value_type, stats< b_type > > set_type; set_type set( ( kwd<id0>::value = 0.9 ) ); std::cout << "a.x_=" << extract_result(set) << std::endl; std::cout << "b.x_=" << extract_result(set) << std::endl; set(0); std::cout << "b.x_=" << extract_result(set) << std::endl; //Output: //a.x_=0.9 //b.x_=0.1 // where 0.9 is expected //b.x_=0.9