std::generate_n

• 1 Parameters
• 2 Return value
• 3 Complexity
• 4 Exceptions
• 5 Possible implementation
• 6 Example
• 7 Defect reports
• 8 See also

The signature of the function should be equivalent to the following:

The type Ret must be such that an object of type OutputIt can be dereferenced and assigned a value of type Ret. ​

[edit] Return value

Iterator one past the last element assigned if count > 0, first otherwise.

[edit] Complexity

Exactly std::max (0, count) invocations of g() and assignments.

[edit] Exceptions

The overload with a template parameter named ExecutionPolicy reports errors as follows:

• If execution of a function invoked as part of the algorithm throws an exception and ExecutionPolicy is one of the standard policies, std::terminate is called. For any other ExecutionPolicy, the behavior is implementation-defined.
• If the algorithm fails to allocate memory, std::bad_alloc is thrown.

[edit] Possible implementation

template<class OutputIt, class Size, class Generator>
constexpr // since C++20
OutputIt generate_n(OutputIt first, Size count, Generator g)
{
 for (Size i = 0; i < count; ++i, ++first)
 *first = g();
 
 return first;
}

[edit] Example

#include <algorithm>
#include <functional>
#include <iostream>
#include <iterator>
#include <random>
 
int main()
{
 std::mt19937 rng; // default constructed, seeded with fixed seed
 std::generate_n(std::ostream_iterator <std::mt19937::result_type>(std::cout, " "),
 5, std::ref (rng));
 std::cout << '\n';
}

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[edit] Defect reports

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

[edit] See also