A Separate using
Declaration Is Required for Each Name
Each using
declaration introduces a single namespace member. This behavior lets us be specific about which names we’re using. As an example, we’ll rewrite the program from § 1.2 (p. 6) with using
declarations for the library names it uses:
#include <iostream>// using declarations for names from the standard libraryusing std::cin;using std::cout; using std::endl;int main(){ cout << "Enter two numbers:" << endl; int v1, v2; cin >> v1 >> v2; cout << "The sum of " << v1 << " and " << v2 << " is " << v1 + v2 << endl; return 0;}
The using
declarations for cin
, cout
, and endl
mean that we can use those names without the std::
prefix. Recall that C++ programs are free-form, ...
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