A discard_block_engine random number engine adaptor
produces random numbers
selected from those produced by some base engine e.

The state
x
of a discard_block_engine engine adaptor object x
consists of the state e of its base engine e
and an additional integer n.

The state transition is performed as follows:
If ,
advance the state of e from e to e
and set n to 0.

The generation algorithm
yields the value returned by the last invocation of e()
while advancing e's state as described above.

template<class Engine, size_t p, size_t r> class discard_block_engine { public: // types using result_type = typename Engine::result_type; // engine characteristics static constexpr size_t block_size = p; static constexpr size_t used_block = r; static constexpr result_type min() { return Engine::min(); } static constexpr result_type max() { return Engine::max(); } // constructors and seeding functions discard_block_engine(); explicit discard_block_engine(const Engine& e); explicit discard_block_engine(Engine&& e); explicit discard_block_engine(result_type s); template<class Sseq> explicit discard_block_engine(Sseq& q); void seed(); void seed(result_type s); template<class Sseq> void seed(Sseq& q); // generating functions result_type operator()(); void discard(unsigned long long z); // property functions const Engine& base() const noexcept { return e; }; private: Engine e; // exposition only int n; // exposition only };

In addition to its behavior
pursuant to subclause [rand.req.adapt],
each constructor
that is not a copy constructor
sets n to 0.