| C++
#include
#include
#include
#include
void f(int n1, int n2, int n3, const int& n4, int n5)
{
std::cout << n1 << ' ' << n2 << ' ' << n3 << ' ' << n4 << ' ' << n5 << '\n';
}
int g(int n1)
{
return n1;
}
struct Foo {
void print_sum(int n1, int n2)
{
std::cout << n1+n2 << '\n';
}
int data = 10;
};
int main()
{
using namespace std::placeholders; // for _1, _2, _3...
std::cout << "1) argument reordering and pass-by-reference: ";
int n = 7;
// (_1 and _2 are from std::placeholders, and represent future
// arguments that will be passed to f1)
auto f1 = std::bind(f, _2, 42, _1, std::cref(n), n);
n = 10;
f1(1, 2, 1001); // 1 is bound by _1, 2 is bound by _2, 1001 is unused
// makes a call to f(2, 42, 1, n, 7)
std::cout << "2) achieving the same effect using a lambda: ";
n = 7;
auto lambda = [&ncref=n, n](auto a, auto b, auto /*unused*/) {
f(b, 42, a, ncref, n);
};
n = 10;
lambda(1, 2, 1001); // same as a call to f1(1, 2, 1001)
std::cout << "3) nested bind subexpressions share the placeholders: ";
auto f2 = std::bind(f, _3, std::bind(g, _3), _3, 4, 5);
f2(10, 11, 12); // makes a call to f(12, g(12), 12, 4, 5);
std::cout << "4) bind a RNG with a distribution: ";
std::default_random_engine e;
std::uniform_int_distribution<> d(0, 10);
auto rnd = std::bind(d, e); // a copy of e is stored in rnd
for(int n=0; n<10; ++n)
std::cout << rnd() << ' ';
std::cout << '\n';
std::cout << "5) bind to a pointer to member function: ";
Foo foo;
auto f3 = std::bind(&Foo::print_sum, &foo, 95, _1);
f3(5);
std::cout << "6) bind to a mem_fn that is a pointer to member function: ";
auto ptr_to_print_sum = std::mem_fn(&Foo::print_sum);
auto f4 = std::bind(ptr_to_print_sum, &foo, 95, _1);
f4(5);
std::cout << "7) bind to a pointer to data member: ";
auto f5 = std::bind(&Foo::data, _1);
std::cout << f5(foo) << '\n';
std::cout << "8) bind to a mem_fn that is a pointer to data member: ";
auto ptr_to_data = std::mem_fn(&Foo::data);
auto f6 = std::bind(ptr_to_data, _1);
std::cout << f6(foo) << '\n';
std::cout << "9) use smart pointers to call members of the referenced objects: ";
std::cout << f6(std::make_shared(foo)) << ' '
<< f6(std::make_unique(foo)) << '\n';
} |