The Header <tuple>

Listing 4

#include <tuple>
#include <utility>
#include <iostream>
using std::tr1::tuple; using std::tr1::tie; using std::tr1::get;
using std::tr1::ignore; using std::tr1::make_tuple; using std::tr1::ref;
using std::cout;

static tuple<double, double, double> get_location(double base)
  { // trivial function that returns a tuple object
  return make_tuple(base, base + 1.0, base + 2.0);
  }

static void show(double x, double y, double z)
  { // show three values
  cout << '(' << x << ',' << y << ',' << z << ')' << '\n';
  }

int main()
  { // demonstrate use of tie and ignore
  double x, y, z;
  // the hard way:
  tuple<double, double, double> tpl = get_location(0.0);
  x = get<0>(tpl);
  y = get<1>(tpl);
  z = get<2>(tpl);
  show(x, y, z);
  // the not-quite-so-hard way:
  make_tuple(ref(x), ref(y), ref(z)) = get_location(3.0);
  show(x, y, z);
  // the easy way:
  tie(x, y, z) = get_location(6.0);
  show(x, y, z);
  // get z only:
  tie(ignore, ignore, z) = get_location(9.0);
  show(x, y, z);
  return 0;
  }