cpp-bignumber/include/math/bigdecimal.h

//
//  bigdecimal.h
//  bigdecimal
//
//  Created by Sam Jaffe on 7/3/17.
//

#pragma once

#include <string>
#include <vector>

namespace math {
  class bigdecimal {
  private:
    template <typename Int>
    using is_signed_t =
        typename std::enable_if<std::numeric_limits<Int>::is_integer &&
                                    std::numeric_limits<Int>::is_signed,
                                void *>::type;
    template <typename Int>
    using is_unsigned_t =
        typename std::enable_if<std::numeric_limits<Int>::is_integer &&
                                    !std::numeric_limits<Int>::is_signed,
                                void *>::type;

  public:
    using data_type = std::vector<int32_t>;
    static bigdecimal const ZERO, ONE, NEGATIVE_ONE;
    static constexpr int32_t const MAX_SEG{999999999};
    static constexpr int32_t const OVER_SEG{1000000000};
    static constexpr int32_t const SEG_DIGITS{9};

  public:
    bigdecimal();

    template <typename Value>
    bigdecimal(Value && value, int32_t scale) : bigdecimal(value) {
      rescale(scale);
    }

    template <typename Int>
    bigdecimal(Int value, is_signed_t<Int> = nullptr)
        : bigdecimal(value < 0,
                     static_cast<uint64_t>(value < 0 ? -value : value)) {}

    template <typename Int>
    bigdecimal(Int value, is_unsigned_t<Int> = nullptr)
        : bigdecimal(false, static_cast<uint64_t>(value)) {}

    bigdecimal(long double);
    bigdecimal(char const *);

    int32_t scale() const { return scale_; }
    void rescale(int32_t);
    void set_value(bigdecimal const &);

    bigdecimal operator-() const;

    friend bigdecimal operator+(bigdecimal, bigdecimal const &);
    friend bigdecimal operator-(bigdecimal, bigdecimal const &);
    friend bigdecimal operator*(bigdecimal, bigdecimal const &);
    friend bigdecimal operator/(bigdecimal, bigdecimal const &);
    friend bigdecimal & operator+=(bigdecimal &, bigdecimal const &);
    friend bigdecimal & operator-=(bigdecimal &, bigdecimal const &);
    friend bigdecimal & operator*=(bigdecimal &, bigdecimal const &);
    friend bigdecimal & operator/=(bigdecimal &, bigdecimal const &);

    friend bool operator==(bigdecimal const &, bigdecimal const &);
    friend bool operator!=(bigdecimal const &, bigdecimal const &);
    friend bool operator<=(bigdecimal const &, bigdecimal const &);
    friend bool operator<(bigdecimal const &, bigdecimal const &);
    friend bool operator>=(bigdecimal const &, bigdecimal const &);
    friend bool operator>(bigdecimal const &, bigdecimal const &);

    std::string to_string() const;

  private:
    bigdecimal(bool, uint64_t);
    void set_scale(int32_t);
    void subtract_impl(bigdecimal const &, bool);

    friend void swap(bigdecimal & rhs, bigdecimal & lhs) {
      using std::swap;
      swap(rhs.is_negative, lhs.is_negative);
      swap(rhs.scale_, lhs.scale_);
      swap(rhs.steps_, lhs.steps_);
      swap(rhs.data, lhs.data);
    }

    bool is_negative;
    int32_t scale_{0}, steps_{0};
    data_type data{};
  };
}