for(int i = 0; i < 9; ++i) {
    for(int j = 0; j < 9; ++i) {
    //...
        for(int k = 0; k < 9; ++k) { //N-th loop

void doRecursion(int baseCondition){

   if(baseCondition==0) return;

   //place your code here

   doRecursion(baseCondition-1);
}

struct multi_index
{
    std::vector<int> min_ind;
    std::vector<int> max_ind;
    std::vector<int> ind;
    bool _end = false;

    multi_index(int N, int _max, int _min = 0)
      : min_ind(N,_min)
      , max_ind(N,_max)
      , ind(N, _min)
    {}

    //possibly other constructors taking vectors for min_ind and max_ind

    auto& operator++()
    {
        // increase first index i for which ind[i] < max_ind[i]
        // set all indices j < i equal to min_ind[j]
        // if no index found to increase, set end = true
        return *this;
    }
   auto operator[](int i) const { return ind[i]; }
   auto end() const { return _end; }
   operator bool() const { return !_end; }
};

int N=5;
for(auto m=multi_index(N,9); !m.end(); ++m)
{
    // now m[i] holds index of i-th loop
}

void loop_function(/*params*/,int N){
for(int i=0;i<9;++i){
    if(N>0) loop_function(/*new params*/,N-1);
}

void runNextNestedFor(std::vector<int> counters, int index)
{
     for(counters[index] = 0; counters[index] < 9; ++counters[index]) {
       // DO
       if(index!=N)
          runNextNestedFor(counters, index+1);
     }
}

std::vectors<int> counters(N);
runNextNestedFor(counters, 0);

#ifndef NESTEDLOOP_HPP
#define NESTEDLOOP_HPP
#include <vector>

namespace nestedLoop{

    class nestedLoop {
        public:
            //Variables
            std::vector<int> maxes;
            std::vector<int> idxes; //The last element is used for boundary control
            int N=0;
            int nestLevel=0;

            nestedLoop();
            nestedLoop(int,int);
            nestedLoop(int,std::vector<int>);

            void reset(int numberOfNests, int Max);
            void reset(int numberOfNests, std::vector<int> theMaxes);

            bool next();
            void jumpNest(int theNest);

        private:
            void clear();
    };

    //Initialisations
    nestedLoop::nestedLoop(){}

    nestedLoop::nestedLoop(int numberOfNests, int Max) {
        reset(numberOfNests, Max);
    }

    nestedLoop::nestedLoop(int numberOfNests, std::vector<int> theMaxes) {
        reset(numberOfNests,  theMaxes);
    }

    void nestedLoop::clear(){
        maxes.clear();
        idxes.clear();
        N = 0;
        nestLevel = 0;
    }

    //Reset the scene
    void nestedLoop::reset(int numberOfNests, int Max){
        std::vector<int> theMaxes;
        for(int i =0; i < numberOfNests; i++) theMaxes.push_back(Max);
        reset(numberOfNests, theMaxes);
    }

    void nestedLoop::reset(int numberOfNests, std::vector<int> theMaxes){
        clear();
        N = numberOfNests;

        maxes=theMaxes;

        idxes.push_back(-1);
        for(int i=1; i<N; i++) idxes.push_back(theMaxes[i]-1);
    }

    bool nestedLoop::next(){
        idxes[N-1]+=1;

        for(int i=N-1; i>=0; i--){
            if(idxes[i]>=maxes[i]) {
                idxes[i] = 0;

                if(i){ //actually, if i > 0 is needed
                    idxes[i-1] += 1;
                }else{
                    return false;
                }
            }else{
                nestLevel = i;
                break;
            }
        }
        return true;
    }

    void nestedLoop::jumpNest(int theNest){
        for(int i = N-1; i>theNest; i--) {
            idxes[i] = maxes[i]-1;
        }
    }
}
#endif // NESTEDLOOP_HPP

#include <iostream>
#include "stlvecs.hpp"
#include "nestedLoop.hpp"

int main(){
    nestedLoop::nestedLoop looper;
    std::vector<int> maxes = {2, 3, 2, 2};
    looper.reset(4,maxes);
    int i = 0;
    while(looper.next()){
        std::cout << "Indices: " << looper.idxes << ", Last nest incremented: " << looper.nestLevel << std::endl;
        if(i == 5){
            std::cout << "...Jump Second Nest (index 1)..." << std::endl;
            looper.jumpNest(1);
        }
        i++;
    }
}

/* Expected output
Indices: 4  0 0 0 0 , Last nest incremented: 0
Indices: 4  0 0 0 1 , Last nest incremented: 3
Indices: 4  0 0 1 0 , Last nest incremented: 2
Indices: 4  0 0 1 1 , Last nest incremented: 3
Indices: 4  0 1 0 0 , Last nest incremented: 1
Indices: 4  0 1 0 1 , Last nest incremented: 3
...Jump Second Nest (index 1)...
Indices: 4  0 2 0 0 , Last nest incremented: 1
Indices: 4  0 2 0 1 , Last nest incremented: 3
Indices: 4  0 2 1 0 , Last nest incremented: 2
Indices: 4  0 2 1 1 , Last nest incremented: 3
Indices: 4  1 0 0 0 , Last nest incremented: 0
Indices: 4  1 0 0 1 , Last nest incremented: 3
Indices: 4  1 0 1 0 , Last nest incremented: 2
Indices: 4  1 0 1 1 , Last nest incremented: 3
Indices: 4  1 1 0 0 , Last nest incremented: 1
Indices: 4  1 1 0 1 , Last nest incremented: 3
Indices: 4  1 1 1 0 , Last nest incremented: 2
Indices: 4  1 1 1 1 , Last nest incremented: 3
Indices: 4  1 2 0 0 , Last nest incremented: 1
Indices: 4  1 2 0 1 , Last nest incremented: 3
Indices: 4  1 2 1 0 , Last nest incremented: 2
Indices: 4  1 2 1 1 , Last nest incremented: 3
*/

#include <iostream>

using namespace std;

void doThingWithNumber(const int* digits, int numDigits)
{
    int i;
    for (i = numDigits-1; i>=0; i--)
        cout << digits[i];
    cout << endl;
}

void loopOverAllNumbers(int numDigits)
{
    int* digits = new int [numDigits];
    int i;
    for (i = 0; i< numDigits; i++)
        digits[i] = 0;

    int maxDigit = 0;
    while (maxDigit < numDigits) {
        doThingWithNumber(digits, numDigits);
        for (i = 0; i < numDigits; i++) {
            digits[i]++;
            if (digits[i] < 10)
                break;
            digits[i] = 0;
        }
        if (i > maxDigit)
            maxDigit = i;
    }
}

int main()
{
    loopOverAllNumbers(3);
    return 0;
}

unsigned int dim = 3;
unsigned int top = 5;
std::vector<unsigned int> m(dim, 0);
for (unsigned int i = 0; i < pow(top,dim); i++)
{
    // What you want to do comes here
    //      |
    //      |
    //      v
    // -----------------------------------
    for (unsigned int j = 0; j < dim; j++)
    {
        std::cout << m[j] << ",";
    }
    std::cout << std::endl;
    // -----------------------------------

    // Increment m
    if (i == pow(top, dim) - 1) break;
    unsigned int index_to_increment = dim - 1;
    while(m[index_to_increment] == (top-1)) {
        index_to_increment -= 1;
    }
    m[index_to_increment] += 1;
    for (unsigned int j = index_to_increment + 1; j < dim; j++)
    {
        m[j] = 0;
    }
}