Method FilterGenerator

tutorials/external/catch.hpp:3739–3751

    public:
        template <typename P = Predicate>
        FilterGenerator(P&& pred, GeneratorWrapper<T>&& generator):
            m_generator(std::move(generator)),
            m_predicate(std::forward<P>(pred))
        {
            if (!m_predicate(m_generator.get())) {
                // It might happen that there are no values that pass the
                // filter. In that case we throw an exception.
                auto has_initial_value = next();
                if (!has_initial_value) {
                    Catch::throw_exception(GeneratorException("No valid value found in filtered generator"));
                }
            }
        }

        T const& get() const override {
            return m_generator.get();