initializer_list
You can use initializer_list
objects in your code by including the initializer_list
header file. The template class has begin()
and end()
members, and you can use them to access list elements. It also has a size()
member that returns the number of elements. Listing 16.22 shows a simple example using initializer_list
. It requires a compiler that supports this C++11 feature.
// ilist.cpp -- use initializer_list (C++11 feature)
#include <iostream>
#include <initializer_list>
double sum(std::initializer_list<double> il);
double average(const std::initializer_list<double> & ril);
int main()
{
using std::cout;
cout << "List 1: sum = " << sum({2,3,4})
<<", ave = " << average({2,3,4}) << '
';
std::initializer_list<double> dl = {1.1, 2.2, 3.3, 4.4, 5.5};
cout << "List 2: sum = " << sum(dl)
<<", ave = " << average(dl) << '
';
dl = {16.0, 25.0, 36.0, 40.0, 64.0};
cout << "List 3: sum = " << sum(dl)
<<", ave = " << average(dl) << '
';
return 0;
}
double sum(std::initializer_list<double> il)
{
double tot = 0;
for (auto p = il.begin(); p !=il.end(); p++)
tot += *p;
return tot;
}
double average(const std::initializer_list<double> & ril)
{
double tot = 0;
int n = ril.size();
double ave = 0.0;
if (n > 0)
{
for (auto p = ril.begin(); p !=ril.end(); p++)
tot += *p;
ave = tot / n;
}
return ave;
}
List 1: sum = 9, ave = 3
List 2: sum = 16.5, ave = 3.3
List 3: sum = 181, ave = 36.2
3.149.241.250