std::generate

template <class ForwardIterator, class Generator>  void generate (ForwardIterator first, ForwardIterator last, Generator gen);

Generate values for range with function

Assigns the value returned by successive calls to gen to the elements in the range [first,last).

The behavior of this function template is equivalent to:

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

Parameters

first, last: Forward iterators to the initial and final positions in a sequence. The range affected is [first,last), which contains all the elements between first and last, including the element pointed by first but not the element pointed by last.
gen: Generator function that is called with no arguments and returns some value of a type convertible to those pointed by the iterators.
This can either be a function pointer or a function object.

Return value

none

Example

// generate algorithm example
#include <iostream>     // std::cout
#include <algorithm>    // std::generate
#include <vector>       // std::vector
#include <ctime>        // std::time
#include <cstdlib>      // std::rand, std::srand

// function generator:
int RandomNumber () { return (std::rand()%100); }

// class generator:
struct c_unique {
  int current;
  c_unique() {current=0;}
  int operator()() {return ++current;}
} UniqueNumber;

int main () {
  std::srand ( unsigned ( std::time(0) ) );

  std::vector<int> myvector (8);

  std::generate (myvector.begin(), myvector.end(), RandomNumber);

  std::cout << "myvector contains:";
  for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  std::generate (myvector.begin(), myvector.end(), UniqueNumber);

  std::cout << "myvector contains:";
  for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';
 
  return 0;
}

A possible output:

myvector contains: 57 87 76 66 85 54 17 15
myvector contains: 1 2 3 4 5 6 7 8

Complexity

Linear in the distance between first and last: Calls gen and performs an assignment for each element.

Data races

The objects in the range [first,last) are modified (each object is accessed exactly once).

Exceptions

Throws if any of gen, the element assignments or the operations on iterators throws.
Note that invalid arguments cause undefined behavior.