seed_seq Class
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The latest version of this topic can be found at seed_seq Class.
Stores a vector of unsigned integer values that can supply a randomized seed for a random-number engine.
class seed_seq
{
public: // types
typedef unsigned int result_type;
// constructors
seed_seq();
template <class T>
seed_seq(initializer_list<T>
initlist);
template <class InputIterator>
seed_seq(InputIterator begin, InputIterator end);
// generating functions
template <class RandomAccessIterator>
void generate(RandomAccessIterator begin, RandomAccessIterator end);
// property functions
size_t size() const;
template <class OutputIterator>
void param(OutputIterator dest) const;
// no copy functions
seed_seq(const seed_seq&) = delete;
void operator=(const seed_seq&) = delete;
};
typedef unsigned int result_type;
The type of the elements of the seed sequence. A 32-bit unsigned integer type.
seed_seq();
Default constructor, initializes to have an empty internal sequence.
template<class T>seed_seq(initializer_list<T> initlist);
Uses initlist to set the internal sequence.T must be an integer type.
template<class InputIterator>seed_seq(InputIterator begin, InputIterator end);
Initializes the internal sequence using all elements in the input iterator range provided.iterator_traits<InputIterator>::value_type must be an integer type.
Generating Functions
template<class RandomAccessIterator> void generate(RandomAccessIterator begin, RandomAccessIterator end);
Populates the elements of the provided sequence using an internal algorithm. This algorithm is affected by the internal sequence with which seed_seq was initialized.
Does nothing if begin == end.
Property Functions
size_t size() const;
Returns the number of elements in the seed_seq.
template<class OutputIterator> void param(OutputIterator dest) const;
Copies the internal sequence into the output iterator dest.
The following code example exercises the three constructors and generates output from the resulting seed_seq instances when assigned to an array. For an example that uses seed_seq with a random number generator, see <random>.
#include <iostream> #include <random> #include <string> #include <array> using namespace std; void test(const seed_seq& sseq) { cout << endl << "seed_seq::size(): " << sseq.size() << endl; cout << "seed_seq::param(): "; ostream_iterator<unsigned int> out(cout, " "); sseq.param(out); cout << endl; cout << "Generating a sequence of 5 elements into an array: " << endl; array<unsigned int, 5> seq; sseq.generate(seq.begin(), seq.end()); for (unsigned x : seq) { cout << x << endl; } } int main() { seed_seq seed1; test(seed1); seed_seq seed2 = { 1701, 1729, 1791 }; test(seed2); string sstr = "A B C D"; // seed string seed_seq seed3(sstr.begin(), sstr.end()); test(seed3); }
seed_seq::size(): 0 seed_seq::param(): Generating a sequence of 5 elements into an array: 505382999 163489202 3932644188 763126080 73937346 seed_seq::size(): 3 seed_seq::param(): 1701 1729 1791 Generating a sequence of 5 elements into an array: 1730669648 1954224479 2809786021 1172893117 2393473414 seed_seq::size(): 7 seed_seq::param(): 65 32 66 32 67 32 68 Generating a sequence of 5 elements into an array: 3139879222 3775111734 1084804564 2485037668 1985355432
Member functions of this class do not throw exceptions.
Header: <random>
Namespace: std