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;
};
Members
Constructors
Signature |
Description |
|---|---|
|
Default constructor, initializes with an empty internal sequence. |
|
Uses initlist to set the internal sequence. T must be an integer type. |
|
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
Signature |
Description |
|---|---|
|
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
Signature |
Description |
|---|---|
|
Returns the number of elements in the seed_seq. |
|
Copies the internal sequence into the output iterator dest. |
Example
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);
}
Output
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
Remarks
Member functions of this class will not throw exceptions.
Requirements
Header: <random>
Namespace: std