Assigns the result ofsuccessive invocations of the function objectgen to each element in the range[first, first+ n), if0< n. Does nothing otherwise.

The function-like entities described on this page arealgorithm function objects (informally known asniebloids), that is:

• Explicit template argument lists cannot be specified when calling any of them.
• None of them are visible toargument-dependent lookup.
• When any of them are found bynormal unqualified lookup as the name to the left of the function-call operator,argument-dependent lookup is inhibited.

[edit]Parameters

[edit]Return value

Iterator one past the last element assigned if0< count,first otherwise.

[edit]Complexity

Exactlyn invocations ofgen() and assignments.

[edit]Possible implementation

struct generate_n_fn{template<std::input_or_output_iterator O,std::copy_constructible F>    requiresstd::invocable<F&>&&std::indirectly_writable<O,std::invoke_result_t<F&>>constexpr O operator()(O first,std::iter_difference_t<O> n, F gen)const{for(; n-->0;*first=std::invoke(gen),++first){}return first;}}; inlineconstexpr generate_n_fn generate_n{};

[edit]Example

#include <algorithm>#include <array>#include <iostream>#include <random>#include <string_view> auto dice(){staticstd::uniform_int_distribution<int> distr{1,6};staticstd::random_device engine;staticstd::mt19937 noise{engine()};return distr(noise);} void print(constauto& v,std::string_view comment){for(int i: v)std::cout<< i<<' ';std::cout<<'('<< comment<<")\n";} int main(){std::array<int,8> v;     std::ranges::generate_n(v.begin(), v.size(), dice);    print(v,"dice");     std::ranges::generate_n(v.begin(), v.size(),[n{0}] mutable{return n++;});// same effect as std::iota(v.begin(), v.end(), 0);    print(v,"iota");}

5 5 2 2 6 6 3 5 (dice)0 1 2 3 4 5 6 7 (iota)

[edit]See also

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