# C++ named requirements: RandomNumberEngineAdaptor

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< cpp‎ | named req

A RandomNumberEngineAdaptor is a RandomNumberEngine that transforms the output of another RandomNumberEngine, the latter of which is termed a base engine.

### Requirements

Given

- B, a RandomNumberEngine
- b, an object of type B
- A, a RandomNumberEngineAdaptor, adapting B as a base engine
- a, an object of type A

function | semantics
--- | ---
A::A(); | The base engine is initialized as if by its default constructor.
bool operator==(const A& lhs, const A& rhs); | Returns whether lhs's base engine is equal to rhs's base engine or not.
A::A(result_type s); | The base engine is initialized with s.
template<class Sseq> A::A(Sseq& q); | The base engine is initialized with q.
void seed(); | Invokes b.seed().
void seed(result_type s); | Invokes b.seed(s).
template<class Sseq> void seed(Sseq& q); | Invokes b.seed(q).

Furthermore

- The complexity of each function of A does not exceed the complexity of the function of B
- The state of A includes the state of B
- The size of A's state is no less than the size of b
- Copying A's state includes copying B's state
- The textual representation of A includes the textual representation of B

### Standard library

The following standard library facilities satisfy RandomNumberEngineAdaptor:

discard_block_engine (C++11) | discards some output of a random number engine (class template)
independent_bits_engine (C++11) | packs the output of a random number engine into blocks of a specified number of bits (class template)
shuffle_order_engine (C++11) | delivers the output of a random number engine in a different order (class template)

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