core/range/type_traits.hpp

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// -----------------------------------------------------------------------------------------------------
// Copyright (c) 2006-2022, Knut Reinert & Freie Universität Berlin
// Copyright (c) 2016-2022, Knut Reinert & MPI für molekulare Genetik
// This file may be used, modified and/or redistributed under the terms of the 3-clause BSD-License
// shipped with this file and also available at: https://github.com/seqan/seqan3/blob/master/LICENSE.md
// -----------------------------------------------------------------------------------------------------
 
#pragma once
 
#include <iterator>
#include <ranges>
#include <type_traits>
 
#include <seqan3/core/detail/iterator_traits.hpp>
#include <seqan3/core/platform.hpp>
#include <seqan3/utility/type_traits/basic.hpp>
 
// TODO(h-2): add innermost_reference instead of or addition to range_innermost_value?
 
//NOTE(h-2): for the range overloads we explicitly forbid that the type is iteratoer
// because some types are actually both (e.g. std::directory_iterator)
 
namespace seqan3::detail
{
 
template <typename t>
concept has_range_value_type = requires { typename std::ranges::range_value_t<std::remove_cvref_t<t>>; };
 
template <bool const_range, typename range_t>
using maybe_const_range_t = std::conditional_t<const_range, range_t const, range_t>;
 
template <bool const_range, typename range_t>
using maybe_const_iterator_t = std::ranges::iterator_t<maybe_const_range_t<const_range, range_t>>;
 
template <bool const_v, typename range_t>
using maybe_const_sentinel_t = std::ranges::sentinel_t<maybe_const_range_t<const_v, range_t>>;
 
template <typename unary_predicate_fn_t, typename urng_t>
concept indirect_unary_predicate_on_range =
    std::ranges::range<urng_t> && std::indirect_unary_predicate<unary_predicate_fn_t, std::ranges::iterator_t<urng_t>>;
} // namespace seqan3::detail
 
namespace seqan3
{
 
// ----------------------------------------------------------------------------
// range_innermost_value
// ----------------------------------------------------------------------------
 
template <typename t>
    requires detail::has_range_value_type<t>
struct range_innermost_value
{
    using type = std::ranges::range_value_t<std::remove_cvref_t<t>>;
};
 
template <typename t>
    requires detail::has_range_value_type<t>
          && detail::has_range_value_type<std::ranges::range_value_t<std::remove_cvref_t<t>>>
struct range_innermost_value<t>
{
    using type = typename range_innermost_value<std::ranges::range_value_t<std::remove_cvref_t<t>>>::type;
};
 
template <typename t>
using range_innermost_value_t = typename range_innermost_value<t>::type;
 
// ----------------------------------------------------------------------------
// range_dimension_v
// ----------------------------------------------------------------------------
 
template <typename t>
    requires detail::has_range_value_type<t>
constexpr size_t range_dimension_v = 1;
 
template <typename t>
    requires detail::has_range_value_type<t>
              && detail::has_range_value_type<std::ranges::range_value_t<std::remove_cvref_t<t>>>
constexpr size_t range_dimension_v<t> = range_dimension_v<std::ranges::range_value_t<std::remove_cvref_t<t>>> + 1;
 
} // namespace seqan3