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Simplify is_output_iterator

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This commit is contained in:
Victor Zverovich
2020-10-20 13:35:31 -07:00
parent da8278e1e3
commit e3b4c22ec9
5 changed files with 47 additions and 57 deletions
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39
include/fmt/core.h
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@@ -801,8 +801,8 @@ template <typename T> class iterator_buffer<T*, T> final : public buffer<T> {
template <typename Container>
class iterator_buffer<std::back_insert_iterator<Container>,
enable_if_t<is_contiguous<Container>::value,
typename Container::value_type>> final
: public buffer<typename Container::value_type> {
typename Container::value_type>>
final : public buffer<typename Container::value_type> {
private:
Container& container_;
@@ -1371,23 +1371,15 @@ struct iterator_category<It, void_t<typename It::iterator_category>> {
using type = typename It::iterator_category;
};
// Detect if *any* given type models the OutputIterator concept.
template <typename It> class is_output_iterator {
// Check for mutability because all iterator categories derived from
// std::input_iterator_tag *may* also meet the requirements of an
// OutputIterator, thereby falling into the category of 'mutable iterators'
// [iterator.requirements.general] clause 4. The compiler reveals this
// property only at the point of *actually dereferencing* the iterator!
template <typename U>
static decltype(*(std::declval<U>())) test(std::input_iterator_tag);
template <typename U> static char& test(std::output_iterator_tag);
template <typename U> static const char& test(...);
template <typename It, typename T, typename Enable = void>
struct is_output_iterator : std::false_type {};
using type = decltype(test<It>(typename iterator_category<It>::type{}));
public:
enum { value = !std::is_const<remove_reference_t<type>>::value };
};
template <typename It, typename T>
struct is_output_iterator<
It, T,
void_t<typename iterator_category<It>::type,
decltype(*std::declval<It>() = std::declval<T>())>>
: std::true_type {};
template <typename OutputIt>
struct is_back_insert_iterator : std::false_type {};
@@ -1983,7 +1975,7 @@ inline void vprint_mojibake(std::FILE*, string_view, format_args) {}
// GCC 8 and earlier cannot handle std::back_insert_iterator<Container> with
// vformat_to<ArgFormatter>(...) overload, so SFINAE on iterator type instead.
template <typename OutputIt, typename S, typename Char = char_t<S>,
FMT_ENABLE_IF(detail::is_output_iterator<OutputIt>::value)>
FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, Char>::value)>
OutputIt vformat_to(
OutputIt out, const S& format_str,
basic_format_args<buffer_context<type_identity_t<Char>>> args) {
@@ -2004,7 +1996,8 @@ OutputIt vformat_to(
\endrst
*/
template <typename OutputIt, typename S, typename... Args,
FMT_ENABLE_IF(detail::is_output_iterator<OutputIt>::value&&
typename Char = char_t<S>,
FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, Char>::value&&
detail::is_string<S>::value)>
inline OutputIt format_to(OutputIt out, const S& format_str, Args&&... args) {
const auto& vargs = fmt::make_args_checked<Args...>(format_str, args...);
@@ -2019,7 +2012,7 @@ template <typename OutputIt> struct format_to_n_result {
};
template <typename OutputIt, typename Char, typename... Args,
FMT_ENABLE_IF(detail::is_output_iterator<OutputIt>::value)>
FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, Char>::value)>
inline format_to_n_result<OutputIt> vformat_to_n(
OutputIt out, size_t n, basic_string_view<Char> format_str,
basic_format_args<buffer_context<type_identity_t<Char>>> args) {
@@ -2037,8 +2030,8 @@ inline format_to_n_result<OutputIt> vformat_to_n(
\endrst
*/
template <typename OutputIt, typename S, typename... Args,
FMT_ENABLE_IF(detail::is_string<S>::value&&
detail::is_output_iterator<OutputIt>::value)>
FMT_ENABLE_IF(detail::is_string<S>::value&& detail::
is_output_iterator<OutputIt, char_t<S>>::value)>
inline format_to_n_result<OutputIt> format_to_n(OutputIt out, size_t n,
const S& format_str,
const Args&... args) {