cpp-bignumber/include/math/bigdecimal.h

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

#pragma once

#include <string>
#include <vector>

#include "number_format.h"

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(number_format const & fmt = default_fmt) 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{};
};
}