Access element of pointed std::vector

Question

I have a function where I provide a pointer to a std::vector.

I want to make x = to vector[element] but i'm getting compiler errors.

I'm doing:

void Function(std::vector<int> *input)
{
   int a;
   a = *input[0];
}

What is the right way to do this? Thanks

Answer 1

Should be:

void Function(std::vector<int> *input)
{
    // note: why split the initialization of a onto a new line?
    int a = (*input)[0]; // this deferences the pointer (resulting in)
                         // a reference to a std::vector<int>), then
                         // calls operator[] on it, returning an int.
}

Otherwise you've got *(input[0]), which is *(input + 0), which is *input. Of course, why not just do:

void Function(std::vector<int>& input)
{
    int a = input[0];
}

And if you don't modify input, mark it as const:

void Function(const std::vector<int>& input)
{
    int a = input[0];
}

Answer 2

You could also go an a syntactic sugar diet and write a = input->operator[](0) ;-)