# std::discard_block_engine

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< cpp‎ | numeric‎ | random

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 pseudo-random 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.

### Template parameters

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 types

Member type | Definition
`result_type` | `Engine::result_type`

### Member functions

(constructor) | constructs the engine adaptor (public member function)
seed | sets the state of the underlying engine (public member function)
base | returns the underlying engine (public member function)

##### Generation

operator() | advances the state of the underlying engine and returns the generated value (public member function)
discard | advances the adaptor's state by a specified amount (public member function)

##### Characteristics

min [static] | gets the smallest possible value in the output range of the underlying engine. (public static member function)
max [static] | gets the largest possible value in the output range of the underlying engine. (public static member function)

### Non-member functions

operator==operator!= | compares the internal states of the adaptors and underlying engines (function)
operator<<operator>> | performs stream input and output on pseudo-random number engine adaptor (function)

### Member objects

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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