std::seed_seq::seed_seq
From cppreference.com
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. After construction,
v is empty.2) The copy constructor is deleted:
std::seed_seq is not copyable.3) Constructs a
.
std::seed_seq with the values in the range [begin, end). Equivalent to default-initializing v followed by for (InputIt s = begin; s != end; ++s) v .push_back(modseed(*s));, where mod_seed(x)=x mod 232.
If std::iterator_traits<InputIt>::value_type is not an integer type, the program is ill-formed.
If
InputIt does not satisfy the requirements of LegacyInputIterator, the behavior is undefined.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 pair of iterators denoting the initial seed sequence |
| il | - | the initial seed sequence |
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 2180 | C++11 | all constructors were non-throwing | only overload (1) is non-throwing |
| LWG 3422 | C++11 | 1. overload (1) was not noexcept 2. overload (4) was not constrainted |
1.made noexcept 2. constrained |