optional.hpp

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#pragma once

#include <zk/config.hpp>

#ifndef ZKPP_OPTIONAL_USE_STD_EXPERIMENTAL
#   define ZKPP_OPTIONAL_USE_STD_EXPERIMENTAL 0
#endif

#ifndef ZKPP_OPTIONAL_USE_CUSTOM
#   define ZKPP_OPTIONAL_USE_CUSTOM 0
#endif

#ifndef ZKPP_OPTIONAL_USE_STD
#   if ZKPP_OPTIONAL_USE_STD_EXPERIMENTAL || ZKPP_OPTIONAL_USE_CUSTOM
#       define ZKPP_OPTIONAL_USE_STD 0
#   else
#       define ZKPP_OPTIONAL_USE_STD 1
#   endif
#endif

#if ZKPP_OPTIONAL_USE_STD
#   define ZKPP_OPTIONAL_INCLUDE  <optional>
#   define ZKPP_OPTIONAL_TEMPLATE std::optional
#   define ZKPP_NULLOPT_TYPE      std::nullopt_t
#   define ZKPP_NULLOPT_VALUE     std::nullopt
#elif ZKPP_OPTIONAL_USE_STD_EXPERIMENTAL
#   define ZKPP_OPTIONAL_INCLUDE  <experimental/optional>
#   define ZKPP_OPTIONAL_TEMPLATE std::experimental::optional
#   define ZKPP_NULLOPT_TYPE      std::experimental::nullopt_t
#   define ZKPP_NULLOPT_VALUE     std::experimental::nullopt
#elif ZKPP_OPTIONAL_USE_CUSTOM
#   if !defined ZKPP_OPTIONAL_INCLUDE || !defined ZKPP_NULLOPT_TYPE || !defined ZKPP_NULLOPT_VALUE
#       error "When ZKPP_OPTIONAL_USE_CUSTOM is set, you must also define ZKPP_OPTIONAL_INCLUDE, ZKPP_NULLOPT_TYPE, and"
#       error "ZKPP_NULLOPT_VALUE."
#   endif
#else
#   error "Unknown type to use for zk::optional, zk::nullopt_t, and zk::nullopt"
#endif

#include ZKPP_OPTIONAL_INCLUDE

namespace zk
{

template <typename T>
using optional = ZKPP_OPTIONAL_TEMPLATE<T>;

using nullopt_t = ZKPP_NULLOPT_TYPE;

using ZKPP_NULLOPT_VALUE;

}