Adding pairs to a vector C++

Question

So, I'm attempting to add pairs to a vector, but they must successfully pass 2 criteria:

1. Their weight or 2nd value is greater than or equal to zero. and throws a string error if it does.
2. The vector must not already contain the key or the first value

It specifically must be done while the function returns a void type, however for some reason, this logic doesn't seem to be working. Any suggestions?

void add(KEY_T key, WEIGHT_T weight)
    {
        bool contains = false;

        if (weight < 0)
        {

            std::cout << "ERROR, invalid weight" << std::endl; //Throw error.
        }

        for (int x = 0; x < _valueToWeightMap.size(); x++)
        {
            if (_valueToWeightMap[x].first == key)
            {
                contains = true;
            }
        }

        if (weight > 0 && contains == false)
            {

            _valueToWeightMap.push_back(std::make_pair(key, weight));

            }

        }

Here is the main:

int main()
{
    DiscreteDistribution<std::string> dist1;

    dist1.add("Helmet", -1);
    dist1.add("Gloves", 5);
    dist1.add("Gloves", 5);
    dist1.add("cloud", 8);

For some reason, I'm not getting an error when I try to add Helmet as -1. Any suggestions?

Answer 1

This line:

        std::cout << "ERROR, invalid weight" << std::endl; //Throw error.

does not do what the comment says (throw an error). This line:

        throw "ERROR, invalid weight"; //Throw error.

does. However, I strongly recommend that you only ever throw exceptions derived from std::exception . This:

        throw std::range_error("ERROR, invalid weight"); //Throw error.

is much better.