C++ In a Nutshell

Name

make_pair function template — Constructs a pair object

Synopsis

template <typename T1, typename T2>
pair<T1,T2> make_pair(T1 a, T2 b);

Constructs a pair<T1,T2> object and initializes it with the values a and b. The advantage of using make_pair over a simple pair<> constructor is that the compiler can deduce the types T1 and T2 from the values a and b. Example 13-39 shows a typical use of make_pair.

Example

Example 13-39. Making pairs of objects

std::map<std::string, int> wordcounts;
wordcounts.insert(std::make_pair("hello", 1));
   
// Functor, suitable for passing to for_each to find minimum and maximum values
// in a range
template<typename T>
class minmax
{
public:
  minmax(  ) : min_(std::numeric_limits<T>::max(  )),
               max_(std::numeric_limits<T>::min(  ))
             {}
  void operator(  )(const T& x) {
    if (x < min_) min_ = x;
    if (max_ < x) max_ = x;
  }
  operator std::pair<T,T>(  ) const {
    returnstd::make_pair(min_, max_);
  }
private:
  T min_;
  T max_;
};
   
int main(  )
{
  std::vector<int> v;
  // Fill v with data.
  std::pair<int,int> mm =
    std::for_each(v.begin(  ), v.end(  ), minmax<int>(  ));
  // Do something with mm.
}

See Also

pair class template