...one of the most highly
regarded and expertly designed C++ library projects in the
world. — Herb Sutter and Andrei
Arguments are also functions? You bet!
Until now, we have been dealing with expressions returning a nullary function. Arguments, on the other hand, evaluate to an N-ary function. An argument represents the Nth argument. There are a few predefined arguments arg1, arg2, arg3, arg4 and so on (and it's BLL counterparts: _1, _2, _3, _4 and so on). Examples:
arg1 // one-or-more argument function that returns its first argument arg2 // two-or-more argument function that returns its second argument arg3 // three-or-more argument function that returns its third argument
argN returns the Nth argument.
int i = 3; char const* s = "Hello World"; std::cout << arg1(i) << std::endl; // prints 3 std::cout << arg2(i, s) << std::endl; // prints "Hello World"
Learn more about arguments here.