Defined in header <random>  

template< class Engine, size_t P, size_t R > class discard_block_engine;  (since C++11) 
discard_block_engine
is a pseudorandom number generator 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. Must be greater than 0. 
R    the number of used numbers per block. Must be greater than 0 and not greater than P 
Type requirements  
Engine must meet the requirements of RandomNumberEngine . 
Member type  Definition 

result_type  Engine::result_type 
constructs the engine adaptor (public member function) 

sets the state of the underlying engine (public member function) 

returns the underlying engine (public member function) 

Generation 

advances the state of the underlying engine and returns the generated value (public member function) 

advances the adaptor's state by a specified amount (public member function) 

Characteristics 

[static]  gets the smallest possible value in the output range of the underlying engine. (public static member function) 
[static]  gets the largest possible value in the output range of the underlying engine. (public static member function) 
compares the internal states of the adaptors and underlying engines (function) 

performs stream input and output on pseudorandom number engine adaptor (function) 
constexpr size_t block_size
[static]  the size of the block, P (public static member constant) 
constexpr size_t used_size
[static]  the number of used numbers per block, R (public static member constant) 
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