c++ - use std::fill to populate vector with increasing numbers

Question

I would like to fill a vector<int> using std::fill, but instead of one value, the vector should contain numbers in increasing order after.

I tried achieving this by iterating the third parameter of the function by one, but this would only give me either vectors filled with 1 or 2 (depending of the position of the ++ operator).

Example:

vector<int> ivec;
int i = 0;
std::fill(ivec.begin(), ivec.end(), i++); // elements are set to 1
std::fill(ivec.begin(), ivec.end(), ++i); // elements are set to 2

Answer 1

Preferably use std::iota like this:

std::vector<int> v(100) ; // vector with 100 ints.
std::iota (std::begin(v), std::end(v), 0); // Fill with 0, 1, ..., 99.

That said, if you don't have any c++11 support (still a real problem where I work), use std::generate like this:

struct IncGenerator {
    int current_;
    IncGenerator (int start) : current_(start) {}
    int operator() () { return current_++; }
};

// ...

std::vector<int> v(100) ; // vector with 100 ints.
IncGenerator g (0);
std::generate( v.begin(), v.end(), g); // Fill with the result of calling g() repeatedly.