std::generate

Defined in header `<algorithm>`
template< class ForwardIt, class Generator > void generate( ForwardIt first, ForwardIt last, Generator g );

Assigns each element in range [first, last) a value generated by the given function object g.

Parameters

first, last - the range of elements to generate

generator function object that will be called.

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

Ret fun();

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

Type requirements

- ForwardIt must meet the requirements of ForwardIterator.

Return value

(none).

Complexity

Exactly std::distance(first, last) invocations of g() and assignments.

Possible implementation

template<class ForwardIt, class Generator>
void generate(ForwardIt first, ForwardIt last, Generator g)
{
    while (first != last) {
        *first++ = g();
    }
}

Example

The following code fills a vector with random numbers:

#include <algorithm>
#include <iostream>
#include <cstdlib>
 
int main()
{
    std::vector<int> v(5);
    std::generate(v.begin(), v.end(), std::rand); // Using the C function rand()
 
    std::cout << "v: ";
    for (auto iv: v) {
        std::cout << iv << " ";
    }
    std::cout << "\n";
 
    // Initialize with default values 0,1,2,3,4 from a lambda function
    // Equivalent to std::iota(v.begin(), v.end(), 0);
    int n = {0};
    std::generate(v.begin(), v.end(), [&n]{ return n++; }); 
 
    std::cout << "v: ";
    for (auto iv: v) {
        std::cout << iv << " ";
    }
    std::cout << "\n";
}

Possible output:

v: 52894 15984720 41513563 41346135 51451456
v: 0 1 2 3 4

fill	assigns a range of elements a certain value (function template)
generate_n	saves the result of N applications of a function (function template)
std::experimental::parallel::generate (parallelism TS)	parallelized version of `std::generate` (function template)