Defined in header <random>  

template< class Engine, std::size_t P, std::size_t R > class discard_block_engine;  (since C++11) 
discard_block_engine
is a pseudorandom number engine adaptor that discards a certain amount of data produced by the base engine. From each block of size P
generated by the base engine, the adaptor keeps only R
numbers, discarding the rest.
Engine    the type of the wrapped engine. 
P    the size of a block. Expected that \(\small{P>0}\)P > 0. 
R    the number of used numbers per block. Expected that \(\small{0<R\le P}\)0 < R ≤ P. 
Type requirements  
Engine must meet the requirements of RandomNumberEngine. 
Member type  Definition 

result_type (C++11)  Engine::result_type 
(C++11)  constructs the engine adaptor (public member function) 
(C++11)  sets the state of the underlying engine (public member function) 
(C++11)  returns the underlying engine (public member function) 
Generation 

(C++11)  advances the state of the underlying engine and returns the generated value (public member function) 
(C++11)  advances the adaptor's state by a specified amount (public member function) 
Characteristics 

[static] (C++11)  gets the smallest possible value in the output range of the underlying engine. (public static member function) 
[static] (C++11)  gets the largest possible value in the output range of the underlying engine. (public static member function) 
(C++11)(C++11)(removed in C++20)  compares the internal states of the adaptors and underlying engines (function) 
(C++11)  performs stream input and output on pseudorandom number engine adaptor (function) 
constexpr size_t block_size
[static] (C++11)  the size of the block, P (public static member constant) 
constexpr size_t used_block
[static] (C++11)  the number of used numbers per block, R (public static member constant) 
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