fixed.hpp

// Copyright Take Vos 2019, 2021.
// 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)
 
#pragma once
 
#include "utility.hpp"
#include "string_tag.hpp"
#include "safe_int.hpp"
#include <type_traits>
#include <limits>
#include <concepts>
 
namespace hi::inline v1 {
 
template<typename T, int M>
struct fixed {
    using value_type = T;
    static constexpr int multiplier = M;
 
    T value;
 
    fixed() = default;
    ~fixed() = default;
    fixed(fixed const &) = default;
    fixed &operator=(fixed const &) = default;
    fixed(fixed &&) = default;
    fixed &operator=(fixed &&) = default;
 
    explicit constexpr fixed(std::floating_point auto other) noexcept : value(static_cast<T>(other * M))
    {
        hi_assert(other >= (std::numeric_limits<T>::min() / M) && other <= (std::numeric_limits<T>::max() / M));
    }
 
    explicit constexpr fixed(std::integral auto other) noexcept : value(static_cast<T>(other) * M)
    {
        hi_assert(other >= (std::numeric_limits<T>::min() / M) && other <= (std::numeric_limits<T>::max() / M));
    }
 
    explicit fixed(std::string const &other) : fixed(stod(other)) {}
 
    constexpr fixed &operator=(std::floating_point auto other) noexcept
    {
        value = static_cast<T>(other * M);
        hi_assert(other >= (std::numeric_limits<T>::min() / M) && other <= (std::numeric_limits<T>::max() / M));
        return *this;
    }
 
    constexpr fixed &operator=(std::integral auto other) noexcept
    {
        value = static_cast<T>(other) * M;
        hi_assert(other >= (std::numeric_limits<T>::min() / M) && other <= (std::numeric_limits<T>::max() / M));
        return *this;
    }
 
    fixed &operator=(std::string const &other)
    {
        value = static_cast<T>(stod(other) * M);
        hi_assert(other >= (std::numeric_limits<T>::min() / M) && other <= (std::numeric_limits<T>::max() / M));
        return *this;
    }
 
    template<std::floating_point O>
    explicit operator O() const noexcept
    {
        return static_cast<O>(value) / M;
    }
 
    template<std::integral O>
    explicit operator O() const noexcept
    {
        return static_cast<O>(value / M);
    }
 
    std::string string() const noexcept
    {
        return std::format("{}", static_cast<double>(value) / M);
    }
 
    static fixed from_raw_value(T value) noexcept
    {
        fixed r;
        r.value = value;
        return r;
    }
 
    [[nodiscard]] constexpr friend bool operator==(fixed const &lhs, fixed const &rhs) noexcept
    {
        return lhs.value == rhs.value;
    }
 
    [[nodiscard]] constexpr friend auto operator<=>(fixed const &lhs, fixed const &rhs) noexcept
    {
        return lhs.value <=> rhs.value;
    }
 
    [[nodiscard]] constexpr friend fixed operator+(fixed const &lhs, fixed const &rhs) noexcept
    {
        return fixed<T, M>::from_raw_value(lhs.value + rhs.value);
    }
 
    [[nodiscard]] constexpr friend fixed operator-(fixed const &lhs, fixed const &rhs) noexcept
    {
        return fixed<T, M>::from_raw_value(lhs.value - rhs.value);
    }
 
    [[nodiscard]] friend std::string to_string(fixed const v)
    {
        return v.string();
    }
 
    friend std::ostream &operator<<(std::ostream &lhs, fixed const &rhs)
    {
        return lhs << rhs.string();
    }
};
 
using money = fixed<safe_int<int64_t>, 100>;
 
} // namespace hi::inline v1