Summary - Namespaces
- C++ course
- Beginner
- Lesson 111/116
- 5 min
Combine namespace, using and alias to write a helper module.
Summary: Helper module
In this summary we will combine namespace, using and alias to build a small helper module. The helper namespace contains a few useful functions; we import them with using and shorten long names with an alias.
The plan: first define the helper namespace with square and cube functions. Then import them with using namespace helper; and add the alias namespace h = helper;. This brings the namespace tools together in a single task.
Practice Build the helper module
Define namespace helper { int square(int x) { return x * x; } }. Add the alias namespace h = helper;. In main, call int n = h::square(5);, print with cout << n << endl;.
Starter code
#include <iostream>
using namespace std;
// Define the helper namespace
// Define the h alias
int main() {
// call square with the alias and print
return 0;
}Sample solution
#include <iostream>
using namespace std;
namespace helper {
int square(int x) { return x * x; }
}
namespace h = helper;
int main() {
int n = h::square(5);
cout << n << endl;
return 0;
}Expected output
25
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Match each tool with its job
| Term | Meaning |
|---|---|
namespace helper |
namespace definition |
using namespace helper |
import |
namespace h = helper |
short name |
2 What does namespace h = helper; provide?
- A new namespace
- A nested namespace
- A using directive
- A short name for helper Correct answer
Explanation: The h alias is a short name for helper.
3 Fill in the blank: using directive
using namespace ____;
int n = square(5);using namespace helper;
int n = square(5);Explanation: using namespace helper makes square callable directly.