Question

I am writing a function for getting datasets from a file and putting them into vectors. The datasets are then used in a calculation. In the file, a user writes each dataset on a line under a heading like ‘Dataset1’. The result is i vectors by the time the function finishes executing. The function works just fine.

The problem is that I don’t know how to get the vectors out of the function! (1) I think I can only return one entity from a function. So I can’t return i vectors. Also, (2) I can’t write the vectors/datasets as function parameters and return them by reference because the number of vectors/datasets is different for each calculation. If there are other possibilities, I am unaware of them.

I’m sure this is a silly question, but am I missing something here? I would be very grateful for any suggestions. Until now, I have not put the vector/dataset extraction code into a function; I have kept it in my main file, where it has worked fine. I would now like to clean up my code by putting all data extraction code into its own function.

For each calculation, I DO know the number of vectors/datasets that the function will find in the file because I have that information written in the file and can extract it. Is there some way I could use this information?

Answer 1

If each vector is of the same type you can return a
std::vector<std::vector<datatype> >

This would look like:

std::vector<std::vector<datatype> > function(arguments) {  
    std::vector<std::vector<datatype> > return_vector;
    for(int i =0; i < rows; ++i) {
       \\ do processing
       return_vector.push_back(resulting_vector);
    }
    return return_vector;
}