std::seed_seq::seed_seq

 

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std::seed_seq

Member functions

seed_seq::seed_seq (C++11)

seed_seq::generate (C++11)

seed_seq::size (C++11)

seed_seq::param (C++11)

 

seed_seq() noexcept;	(1)	(since C++11)
seed_seq( const seed_seq& ) = delete;	(2)	(since C++11)
template< class InputIt > seed_seq( InputIt begin, InputIt end );	(3)	(since C++11)
template< class T > seed_seq( std::initializer_list<T> il );	(4)	(since C++11)

1) The default constructor creates a std::seed_seq object with an initial seed sequence of length zero.

2) The copy constructor is deleted: std::seed_seq is not copyable.

3) Constructs a std::seed_seq with the initial seed sequence obtained by iterating over the range [begin, end) and copying the values obtained by dereferencing the iterator, modulo 232
(that is, the lower 32 bits are copied).

4) Equivalent to seed_seq(il.begin(), il.end()). This constructor enables list-initialization from the list of seed values. This overload participates in overload resolution only if T is an integer type.

Parameters

begin, end	-	the initial seed sequence represented as a pair of input iterators whose std::iterator_traits<>::value_type is an integer type
il	-	std::initializer_list of objects of integer type, providing the initial seed sequence
Type requirements
- InputIt must meet the requirements of LegacyInputIterator.

Exceptions

3-4) Throws std::bad_alloc on allocation failure.

Example

Run this code

#include <iterator>
#include <random>
#include <sstream>
 
int main()
{
    std::seed_seq s1; // default-constructible
    std::seed_seq s2{1, 2, 3}; // can use list-initialization
    std::seed_seq s3 = {-1, 0, 1}; // another form of list-initialization
    int a[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
    std::seed_seq s4(a, a + 10); // can use iterators
    std::istringstream buf("1 2 3 4 5"); 
    std::istream_iterator<int> beg(buf), end;
    std::seed_seq s5(beg, end); // even stream input iterators
}

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 3422	C++11	the default constructor never fails but might be not noexcept; the initializer list constructor disabled list-initialization from iterator pairs	made noexcept; constrained