Skip to content

Instantly share code, notes, and snippets.

@spott
Forked from dscharrer/infix_operator.cpp
Created June 7, 2012 17:24
Show Gist options
  • Save spott/2890180 to your computer and use it in GitHub Desktop.
Save spott/2890180 to your computer and use it in GitHub Desktop.
The proper way to call std::swap
#include <type_traits>
namespace detail {
// No need to give up constexpr for std::forward
template <class T>
constexpr T && forward(typename std::remove_reference<T>::type & t) noexcept {
return static_cast<T &&>(t);
}
template <class T>
constexpr T && forward(typename std::remove_reference<T>::type && t) noexcept {
static_assert(!std::is_lvalue_reference<T>::value,
"Cannot forward rvalue as lvalue.");
return static_cast<T &&>(t);
}
template <
typename Left,
class Op,
typename = typename std::decay<Op>::type::binary_operator_tag
>
struct bound_operator {
Left && left;
Op && op;
constexpr bound_operator(Left && left, Op && op)
: left(forward<Left>(left)), op(forward<Op>(op)) { }
};
} // namespace detail
template <typename Left, class Op>
constexpr detail::bound_operator<Left, Op> operator<(Left && left, Op && op) {
return { detail::forward<Left>(left), detail::forward<Op>(op) };
}
template <typename Left, class Op, typename Right>
constexpr auto operator>(detail::bound_operator<Left, Op> && ref, Right && right)
-> decltype(ref.op(detail::forward<Left>(ref.left), detail::forward<Right>(right))) {
return ref.op(detail::forward<Left>(ref.left), detail::forward<Right>(right));
}
//-------------------------------------------------------------------------
#include <algorithm>
constexpr struct swap_operator {
typedef void binary_operator_tag;
template <typename T>
void operator()(T & a, T & b) const {
std::swap(a, b);
}
} swap = swap_operator();
//-------------------------------------------------------------------------
#include <iostream>
int main() {
int a = 0;
int b = 1;
a <swap> b;
std::cout << "a=" << a << " b=" << b << std::endl;
return 0;
}
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment