Generators.hpp

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//          Copyright Dominic Koepke 2021 - 2022.
// Distributed under the Boost Software License, Version 1.0.
//    (See accompanying file LICENSE_1_0.txt or copy at
//          https://www.boost.org/LICENSE_1_0.txt)
 
#ifndef SIMPLE_VECTOR_GENERATORS_HPP
#define SIMPLE_VECTOR_GENERATORS_HPP
 
#pragma once
 
#include "Concepts.hpp"
 
#include <iterator>
#include <ranges>
#include <type_traits>
 
namespace sl::vec::gen
{
    template <value_type T>
    struct fill
    {
        using value_type = std::remove_cvref_t<T>;
 
        const value_type value{};
 
        constexpr value_type operator ()() const noexcept(std::is_nothrow_copy_constructible_v<value_type>)
        {
            return value;
        }
    };
 
    template <value_type T>
    fill(T) -> fill<T>;
 
    template <value_type T>
        requires std::weakly_incrementable<T>
    struct iota
    {
        using value_type = std::remove_cvref_t<T>;
 
        value_type value{};
 
        constexpr value_type operator ()()
        {
            return value++;
        }
    };
 
    template <value_type T>
    iota(T) -> iota<T>;
 
    template <std::ranges::forward_range TRange>
    class range
    {
    public:
        using range_type = std::conditional_t
        <
            std::ranges::borrowed_range<TRange>,
            TRange,
            std::remove_cvref_t<TRange>
        >;
        using iterator_type = std::ranges::iterator_t<range_type>;
        using value_type = std::ranges::range_value_t<TRange>;
 
        constexpr explicit range(TRange&& range)
            : m_Range{ std::forward<TRange>(range) },
            m_Iterator{ std::ranges::begin(m_Range) }
        {
        }
 
        constexpr value_type operator ()()
        {
            return *m_Iterator++;
        }
 
    private:
        range_type m_Range;
        iterator_type m_Iterator;
    };
 
    template <std::ranges::forward_range TRange>
    range(TRange&&) -> range<TRange>;
 
}
 
#endif