&& generator):
+ m_generator(std::move(generator)),
+ m_predicate(std::forward(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();
+ }
+
+ bool next() override {
+ bool success = m_generator.next();
+ if (!success) {
+ return false;
+ }
+ while (!m_predicate(m_generator.get()) && (success = m_generator.next()) == true);
+ return success;
+ }
+ };
+
+ template
+ GeneratorWrapper filter(Predicate&& pred, GeneratorWrapper&& generator) {
+ return GeneratorWrapper(std::unique_ptr>(pf::make_unique>(std::forward(pred), std::move(generator))));
+ }
+
+ template
+ class RepeatGenerator : public IGenerator {
+ GeneratorWrapper m_generator;
+ mutable std::vector m_returned;
+ size_t m_target_repeats;
+ size_t m_current_repeat = 0;
+ size_t m_repeat_index = 0;
+ public:
+ RepeatGenerator(size_t repeats, GeneratorWrapper&& generator):
+ m_generator(std::move(generator)),
+ m_target_repeats(repeats)
+ {
+ assert(m_target_repeats > 0 && "Repeat generator must repeat at least once");
+ }
+
+ T const& get() const override {
+ if (m_current_repeat == 0) {
+ m_returned.push_back(m_generator.get());
+ return m_returned.back();
+ }
+ return m_returned[m_repeat_index];
+ }
+
+ bool next() override {
+ // There are 2 basic cases:
+ // 1) We are still reading the generator
+ // 2) We are reading our own cache
+
+ // In the first case, we need to poke the underlying generator.
+ // If it happily moves, we are left in that state, otherwise it is time to start reading from our cache
+ if (m_current_repeat == 0) {
+ const auto success = m_generator.next();
+ if (!success) {
+ ++m_current_repeat;
+ }
+ return m_current_repeat < m_target_repeats;
+ }
+
+ // In the second case, we need to move indices forward and check that we haven't run up against the end
+ ++m_repeat_index;
+ if (m_repeat_index == m_returned.size()) {
+ m_repeat_index = 0;
+ ++m_current_repeat;
+ }
+ return m_current_repeat < m_target_repeats;
+ }
+ };
+
+ template
+ GeneratorWrapper repeat(size_t repeats, GeneratorWrapper&& generator) {
+ return GeneratorWrapper(pf::make_unique>(repeats, std::move(generator)));
+ }
+
+ template
+ class MapGenerator : public IGenerator {
+ // TBD: provide static assert for mapping function, for friendly error message
+ GeneratorWrapper m_generator;
+ Func m_function;
+ // To avoid returning dangling reference, we have to save the values
+ T m_cache;
+ public:
+ template
+ MapGenerator(F2&& function, GeneratorWrapper