std::generate_n - cppreference.com (original) (raw)

1. Assigns values, generated by given function object g, to the first count elements in the range beginning at first, if count > 0. Does nothing otherwise.

2. Same as (1), but executed according to policy.

This overload participates in overload resolution only if all following conditions are satisfied:

If Size is not convertible to an integral type, the program is ill-formed.

Contents

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

[edit] Parameters

[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 #include #include #include #include   int main() { std::mt19937 rng; // default constructed, seeded with fixed seed std::generate_n(std::ostream_iteratorstd::mt19937::result_type(std::cout, " "), 5, std::ref(rng)); std::cout << '\n'; }

Output:

3499211612 581869302 3890346734 3586334585 545404204

[edit] Defect reports

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

[edit] See also

| | copy-assigns the given value to N elements in a range (function template) [edit] | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | | assigns the results of successive function calls to every element in a range (function template) [edit] | | | saves the result of N applications of a function(algorithm function object)[edit] |