Copy a char vector to another vector

Question

I'm trying to create a function to copy an vector into another one:

#include <iostream>
#include <vector> 

int clone(std::vector <char> X, std::vector <char> Y){
    for(int i(0);i<X.size();i++){
        Y[i]=X[i];
    }
    return 0;
}

When I call the function, nothing appears on the prompt window.

Answer 1

There are 2 issues with your code. The first is that any modification to Y will not be visible at the call site, since you are passing the vector by value. Instead, you need to pass it by reference.

Second, you are indexing X incorrectly (assuming X is not as large as Y ). Instead, you could just push_back the values.

However, you can even copy vector s directly, so you could do:

int clone(std::vector <char> const &X, std::vector <char> &Y){
    Y = X;
    return 0;
}

At this point, having a named function is rather pointless, since instead of doing something like:

std::vector<char> y;
clone(x, y);

you could simply do:

auto y = x;

which is much more readable.