Hi there, I got nothing outputted from the following sample code on page 360 to 362 of the book "Beyond the C++ Standard". Did I missed something? Thanks in advance. Robert ============== #include <iostream> #include "boost/signals.hpp" // boost book, pp. 360 - 362 bool step0() { std::cout << "Step 0 is OK.\n"; return true; }; bool step1() { std::cout << "Step 1 is not OK. This won't do at all. \n"; return false; }; bool step2() { std::cout << "Step 2 is OK. \n"; return true; }; // we need this one as Combiner class stop_on_failure { public: typedef bool result_type; template<typename InputIterator> bool operator()(InputIterator begin, InputIterator end) const { while (begin != end); { if (!*begin) return false; ++begin; } return true; } }; int main() { boost::signal<bool (), stop_on_failure> sig; sig.connect(0, &step0); sig.connect(1, &step1); sig.connect(2, &step2); bool ok = sig(); if (ok) std::cout << "All system tests clear. \n"; else std::cout << "At least one test failed. Aborting. \n"; return 0; } ==============