std:: generate

Parameters

Complexity

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

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.

Possible implementation

template<class ForwardIt, class Generator>
constexpr //< since C++20
void generate(ForwardIt first, ForwardIt last, Generator g)
{
    for (; first != last; ++first)
        *first = g();
}

Example

#include <algorithm>
#include <iostream>
#include <vector>
 
void println(std::string_view fmt, const auto& v)
{
    for (std::cout << fmt; const auto& e : v)
        std::cout << e << ' ';
    std::cout << '\n';
};
 
 
int f()
{
    static int i;
    return ++i;
}
 
int main()
{
    std::vector<int> v(5);
 
    std::generate(v.begin(), v.end(), f);
    println("v: ", v);
 
    // Initialize with default values 0,1,2,3,4 from a lambda function
    // Equivalent to std::iota(v.begin(), v.end(), 0);
    std::generate(v.begin(), v.end(), [n = 0] () mutable { return n++; });
    println("v: ", v);
}

v: 1 2 3 4 5
v: 0 1 2 3 4

See also