mirror of https://gitee.com/bigwinds/arangodb
62 lines
1.5 KiB
C++
62 lines
1.5 KiB
C++
// Copyright Louis Dionne 2013-2016
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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#include <boost/hana/core/default.hpp>
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#include <boost/hana/core/tag_of.hpp>
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#include <string>
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#include <type_traits>
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namespace hana = boost::hana;
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namespace with_special_base_class {
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//! [special_base_class]
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struct special_base_class { };
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template <typename T>
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struct print_impl : special_base_class {
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template <typename ...Args>
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static constexpr auto apply(Args&& ...) = delete;
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};
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template <typename T>
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struct Printable {
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using Tag = hana::tag_of_t<T>;
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static constexpr bool value = !std::is_base_of<special_base_class, print_impl<Tag>>::value;
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};
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//! [special_base_class]
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//! [special_base_class_customize]
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struct Person { std::string name; };
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template <>
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struct print_impl<Person> /* don't inherit from special_base_class */ {
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// ... implementation ...
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};
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static_assert(Printable<Person>::value, "");
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static_assert(!Printable<void>::value, "");
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//! [special_base_class_customize]
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}
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namespace actual {
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//! [actual]
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template <typename T>
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struct print_impl : hana::default_ {
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template <typename ...Args>
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static constexpr auto apply(Args&& ...) = delete;
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};
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template <typename T>
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struct Printable {
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using Tag = hana::tag_of_t<T>;
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static constexpr bool value = !hana::is_default<print_impl<Tag>>::value;
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};
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//! [actual]
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static_assert(!Printable<void>::value, "");
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}
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int main() { }
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