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How to write this for-loop using std::for_each or std::transform?
vector<vector<int> > int_vectors;

// ... fill int_vectors

vector<int> ints;

for (vector<vector<int> >::const_iterator iter = int_vectors.begin(); iter != int_vectors.end(); ++iter) {
   ints.insert(ints.end(), iter->begin(), iter->end());
}

typedef std::vector<int>::iterator (std::vector<int>::*IteratorGetter)();

std::for_each(int_vectors.begin(), int_vectors.end(),
    std::bind(
        std::bind(
            &std::vector<int>::insert<std::vector<int>::iterator>,
            &ints,
            std::bind((IteratorGetter)&std::vector<int>::end, &ints),
            _1,
            _2
        ),
        std::bind((IteratorGetter)&std::vector<int>::begin, _1),
        std::bind((IteratorGetter)&std::vector<int>::end, _1)
    )
);

typedef std::vector<int> VI;
typedef std::vector<VI> VVI;

VVI int_vectors;
VI ints;

std::for_each(int_vectors.begin(), int_vectors.end(), [&](VI &vec) {
    ints.insert(ints.end(), vec.begin(), vec.end());
});

#include <algorithm>
#include <vector>
#include <iostream>
#include <iterator>

using namespace std;
#define all(v) (v).begin(), (v).end()
#define foreach(it, v) for(auto it = (v).begin(); it != (v).end(); ++it)

void main() {
    vector<int> vi;
    vector<vector<int>> vvi;

    foreach(it, vvi) {
        copy(all(*it), back_inserter(vi));
    }
}