Question

I declared a vector a pairs with:

vector <pair <int, int> > args;

Then I want to push a pair into the vector like this:

args.push_back((1,-1));

It tells me that the left-hand operand of comma has no effect.
Where do I go wrong?

Answer 1

Say args.push_back(std::make_pair(1,-1));. Or any number of alternatives:

// #1
args.push_back(std::pair<int, int>(1,-1));

// #2
typedef std::vector< std::pair<int, int> > pvector;
pvector args;
args.push_back(pvector::value_type(1,-1));

// #3
typedef std::pair<int, int> intpair;
std::vector<intpair> args;
args.push_back(intpair(1,-1));

// #4
args.emplace_back(1, -1);  // sexy

//...