On Mon, Jan 9, 2017 at 2:52 AM, Jonathan Wakely <jwak...@redhat.com> wrote: > On 08/01/17 22:49 -0800, Tim Shen wrote: >> >> On Tue, Jan 3, 2017 at 6:17 AM, Jonathan Wakely <jwak...@redhat.com> >> wrote: >>> >>> On 01/01/17 04:17 -0800, Tim Shen via libstdc++ wrote: >>>> >>>> >>>> +#define _VARIANT_RELATION_FUNCTION_TEMPLATE(__op, __name) \ >>>> + template<typename... _Types> \ >>>> + constexpr bool operator __op(const variant<_Types...>& __lhs, \ >>>> + const variant<_Types...>& __rhs) \ >>>> + { \ >>>> + return __lhs._M##__name(__rhs, >>>> std::index_sequence_for<_Types...>{}); \ >>>> + } \ >>>> +\ >>>> + constexpr bool operator __op(monostate, monostate) noexcept \ >>>> + { return 0 __op 0; } >>>> + >>>> + _VARIANT_RELATION_FUNCTION_TEMPLATE(<, _erased_less_than) >>>> + _VARIANT_RELATION_FUNCTION_TEMPLATE(<=, _erased_less_equal) >>>> + _VARIANT_RELATION_FUNCTION_TEMPLATE(==, _erased_equal) >>>> + _VARIANT_RELATION_FUNCTION_TEMPLATE(!=, _erased_not_equal) >>>> + _VARIANT_RELATION_FUNCTION_TEMPLATE(>=, _erased_greater_than) >>>> + _VARIANT_RELATION_FUNCTION_TEMPLATE(>, _erased_greater) >>> >>> >>> >>> These need double underscore prefixes. >> >> >> Done. > > > I'm sorry, I missed that they get appended to _M to form a member > function name, so they don't need a double underscore. > > But since they all have the same prefix, why not use _M_erased_##name > and just use less_than, less_equal etc. in the macro invocations? > > However, the names are weird, you have >= as greater_than (not > greater_equal) and > as greater (which is inconsistent with < as > less_than). > > So I'd go with: > > _VARIANT_RELATION_FUNCTION_TEMPLATE(<, less) > _VARIANT_RELATION_FUNCTION_TEMPLATE(<=, less_equal) > _VARIANT_RELATION_FUNCTION_TEMPLATE(==, equal) > _VARIANT_RELATION_FUNCTION_TEMPLATE(!=, not_equal) > _VARIANT_RELATION_FUNCTION_TEMPLATE(>=, greater_equal) > _VARIANT_RELATION_FUNCTION_TEMPLATE(>, greater) > >> +#define _VARIANT_RELATION_FUNCTION_TEMPLATE(__op, __name) \ > > > I think we usually use all-caps for macro arguments, so _OP and _NAME, > but it doesn't really matter. > >> + template<size_t... __indices> \ >> + static constexpr bool \ >> + (*_S##__name##_vtable[])(const variant&, const variant&) = \ >> + { &__detail::__variant::__name<const variant&, __indices>... }; >> \ > > > With the suggestions above this would change to use _S_erased_##_NAME > and &__detail::__variant::__erased_##_NAME > >> + template<size_t... __indices> \ >> + constexpr inline bool \ >> + _M##__name(const variant& __rhs, \ >> + std::index_sequence<__indices...>) const \ >> + { \ >> + auto __lhs_index = this->index(); \ >> + auto __rhs_index = __rhs.index(); \ >> + if (__lhs_index != __rhs_index || valueless_by_exception()) \ >> + /* Intentinoal modulo addition. */ \ > > > "Intentional" is spelled wrong, but I think simply "Modulo addition" > is clear enough that it's intentional. > >> + return __lhs_index + 1 __op __rhs_index + 1; \ >> + return _S##__name##_vtable<__indices...>[__lhs_index](*this, >> __rhs); \ >> }
All done. >> >> - template<size_t... __indices> > > > And we'd usually use _Indices for template parameters, but this is > already inconsistent in <variant>. I didn't change this one, since I prefer in-file consistency. That's weird, So let's discuss this. There are several naming style in libstdc++: 1) __underscore_name, for free functions, variables, and namespaces; 2) _CamelCase, for types, template type parameters in some files (e.g. <regex>, I forgot why I did that :/). 3) _Camel_underscore_name, for types in many other files. 4) _S_underscore_name, _M_underscore name, for static and member functions, respectively. There are two questions: *) It seems natural to have (1) for non-type template parameters, since that are also variables. *) _CamelCase vs _Camel_underscore_name? Which one is preferred? > > The patch is OK with those naming tweaks. Thanks, and sorry for the > mixup about the underscores. > No worries! Tested and committed. -- Regards, Tim Shen