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// function::operator bool example
#include <iostream> // std::cout
#include <functional> // std::function, std::plus
int main () {
std::function<int(int,int)> foo,bar;
foo = std::plus<int>();
foo.swap(bar);
std::cout << "foo is " << (foo ? "callable" : "not callable") << ".\n";
std::cout << "bar is " << (bar ? "callable" : "not callable") << ".\n";
return 0;
}
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