49 lines
1.6 KiB
C
49 lines
1.6 KiB
C
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#ifndef C10_UTIL_OPTIONAL_H_
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#define C10_UTIL_OPTIONAL_H_
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#include <optional>
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#include <type_traits>
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// Macros.h is not needed, but it does namespace shenanigans that lots
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// of downstream code seems to rely on. Feel free to remove it and fix
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// up builds.
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namespace c10 {
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// NOLINTNEXTLINE(misc-unused-using-decls)
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using std::bad_optional_access;
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// NOLINTNEXTLINE(misc-unused-using-decls)
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using std::make_optional;
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// NOLINTNEXTLINE(misc-unused-using-decls)
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using std::nullopt;
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// NOLINTNEXTLINE(misc-unused-using-decls)
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using std::nullopt_t;
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// NOLINTNEXTLINE(misc-unused-using-decls)
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using std::optional;
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namespace detail_ {
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// the call to convert<A>(b) has return type A and converts b to type A iff b
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// decltype(b) is implicitly convertible to A
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template <class U>
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constexpr U convert(U v) {
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return v;
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}
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} // namespace detail_
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template <class T, class F>
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constexpr T value_or_else(const optional<T>& v, F&& func) {
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static_assert(
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std::is_convertible_v<typename std::invoke_result_t<F>, T>,
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"func parameters must be a callable that returns a type convertible to the value stored in the optional");
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return v.has_value() ? *v : detail_::convert<T>(std::forward<F>(func)());
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}
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template <class T, class F>
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constexpr T value_or_else(optional<T>&& v, F&& func) {
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static_assert(
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std::is_convertible_v<typename std::invoke_result_t<F>, T>,
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"func parameters must be a callable that returns a type convertible to the value stored in the optional");
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return v.has_value() ? constexpr_move(std::move(v).contained_val())
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: detail_::convert<T>(std::forward<F>(func)());
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}
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} // namespace c10
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#endif // C10_UTIL_OPTIONAL_H_
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