cpp-bignumber/include/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{};
  };
}