slice.hpp

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// -----------------------------------------------------------------------------------------------------
// Copyright (c) 2006-2019, Knut Reinert & Freie Universität Berlin
// Copyright (c) 2016-2019, 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 <stdexcept>

#include <seqan3/io/exception.hpp>
#include <seqan3/range/concept.hpp>
#include <seqan3/range/view/detail.hpp>
#include <seqan3/range/view/drop.hpp>
#include <seqan3/range/view/take.hpp>
#include <seqan3/std/concepts>
#include <seqan3/std/iterator>
#include <seqan3/std/ranges>
#include <seqan3/std/span>
#include <seqan3/std/type_traits>

namespace seqan3::detail
{

// ============================================================================
//  slice_fn (adaptor definition)
// ============================================================================

struct slice_fn
{
    constexpr auto operator()(ptrdiff_t begin_pos, ptrdiff_t end_pos) const noexcept
    {
        return detail::adaptor_from_functor{*this, begin_pos, end_pos};
    }

    template <std::ranges::ViewableRange urng_t>
    constexpr auto operator()(urng_t && urange, ptrdiff_t begin_pos, ptrdiff_t end_pos) const
    {
        if constexpr (std::ranges::SizedRange<urng_t>)
        {
            begin_pos = std::min(begin_pos, static_cast<ptrdiff_t>(std::ranges::size(urange)));
            end_pos = std::min(end_pos, static_cast<ptrdiff_t>(std::ranges::size(urange)));
        }

        if (end_pos < begin_pos)
            throw std::invalid_argument{"end_pos argument to seqan3::view::slice must be >= the begin_pos argument."};

        return std::forward<urng_t>(urange) | view::drop(begin_pos) | view::take(end_pos - begin_pos);
    }

    // does not require special overloads, because view::drop and view::take handle the flattening.
};

} // namespace seqan3::detail

// ============================================================================
//  view::slice (adaptor instance definition)
// ============================================================================

namespace seqan3::view
{

inline constexpr auto slice = detail::slice_fn{};


} // namespace seqan3::view