Creating N nested for-loops

Question

Is there a way to create for-loops of a form

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


        

Answer 1

I use this solution:

unsigned int dim = 3;
unsigned int top = 5;
std::vector 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)) {
        m[index_to_increment] = 0;
        index_to_increment -= 1;
    }
    m[index_to_increment] += 1;
}

It can certainly optimized and adapted, but it works quite well and you don't need to pass parameters to a recursive function. With a separate function to increment the multi-index:

typedef std::vector ivec;
void increment_multi_index(ivec &m, ivec const & upper_bounds)
{
    unsigned int dim = m.size();
    unsigned int i = dim - 1;
    while(m[i] == upper_bounds[i] - 1 && i>0) {
        m[i] = 0;
        i -= 1;
    }
    m[i] += 1;
}

int main() {

    unsigned int dim = 3;
    unsigned int top = 5;
    ivec m(dim, 0);
    ivec t(dim, top);
    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
        increment_multi_index(m, t);
    }

}