CPP: Implementation of Rational

main.cpp

#include <iostream>
#include <sstream>
#include <cmath>
#include <map>
#include <vector>
#include <set>

using namespace std;

class Rational {
public:
  Rational() {
    numerator = 0;
    denominator = 1;
  }

  Rational(int numerator, int denominator) {
    int gcd_modulo = gcd(abs(numerator), abs(denominator));
    if (numerator != 0) {
      if (denominator > 0) {
        this->numerator = numerator / gcd_modulo;
        this->denominator = denominator / gcd_modulo;
      } else {
        this->numerator = -(numerator / gcd_modulo);
        this->denominator = -(denominator / gcd_modulo);
      }
    } else {
      this->numerator = numerator;
      this->denominator = 1;
    }
  }

  int Numerator() const {
    return numerator;
  }

  int Denominator() const {
    return denominator;
  }

private:
  int gcd(int a, int b) {
    while (a > 0 && b > 0) {
      if (a > b) {
        a %= b;
      } else {
        b %= a;
      }
    }
    return a + b;
  }

  signed int numerator;
  int denominator;
};

bool operator==(const Rational &lhs, const Rational &rhs) {
  return lhs.Numerator() == rhs.Numerator() && lhs.Denominator() == rhs.Denominator();
}

bool operator<(const Rational &lhs, const Rational &rhs) {
  return lhs.Numerator() * rhs.Denominator() < rhs.Numerator() * lhs.Denominator();
}

Rational operator+(const Rational &lhs, const Rational &rhs) {
  return {
    lhs.Numerator() * rhs.Denominator() + rhs.Numerator() * lhs.Denominator(),
    lhs.Denominator() * rhs.Denominator()
  };
}

Rational operator-(const Rational &lhs, const Rational &rhs) {
  return {
    lhs.Numerator() * rhs.Denominator() - rhs.Numerator() * lhs.Denominator(),
    lhs.Denominator() * rhs.Denominator()
  };
}

Rational operator*(const Rational &lhs, const Rational &rhs) {
  return {
    lhs.Numerator() * rhs.Numerator(),
    lhs.Denominator() * rhs.Denominator()
  };
}

Rational operator/(const Rational &lhs, const Rational &rhs) {
  return {
    lhs.Numerator() * rhs.Denominator(),
    lhs.Denominator() * rhs.Numerator()
  };
}

ostream& operator<<(ostream &stream, const Rational &rational) {
  stream << rational.Numerator()
         << "/"
         << rational.Denominator();
  return stream;
}

istream& operator>>(istream& stream, Rational& rational) {
  if (stream.tellg() == -1) {
    return stream;
  }
  int numerator = 0;
  int denominator = 1;
  stream >> numerator;
  stream.ignore(1);
  stream >> denominator;
  Rational new_rational = Rational { numerator, denominator };
  rational = new_rational;
  return stream;
}

int main() {
  {
    const Rational r(3, 10);
    if (r.Numerator() != 3 || r.Denominator() != 10) {
      cout << "Rational(3, 10) != 3/10" << endl;
      return 1;
    }
  }

  {
    const Rational r(8, 12);
    if (r.Numerator() != 2 || r.Denominator() != 3) {
      cout << "Rational(8, 12) != 2/3" << endl;
      return 2;
    }
  }

  {
    const Rational r(-4, 6);
    if (r.Numerator() != -2 || r.Denominator() != 3) {
      cout << "Rational(-4, 6) != -2/3" << endl;
      return 3;
    }
  }

  {
    const Rational r(4, -6);
    if (r.Numerator() != -2 || r.Denominator() != 3) {
      cout << "Rational(4, -6) != -2/3" << endl;
      return 3;
    }
  }

  {
    const Rational r(0, 15);
    if (r.Numerator() != 0 || r.Denominator() != 1) {
      cout << "Rational(0, 15) != 0/1" << endl;
      return 4;
    }
  }

  {
    const Rational defaultConstructed;
    if (defaultConstructed.Numerator() != 0 || defaultConstructed.Denominator() != 1) {
      cout << "Rational() != 0/1" << endl;
      return 5;
    }
  }
  {
    const Rational r(-6, -8);
    if (r.Numerator() != 3 || r.Denominator() != 4) {
      cout << "Rational(-6, -8) != 2/3" << endl;
      return 6;
    }
  }
  {
    Rational r1(4, 6);
    Rational r2(2, 3);
    bool equal = r1 == r2;
    if (!equal) {
      cout << "4/6 != 2/3" << endl;
      return 1;
    }
  }

  {
    Rational a(2, 3);
    Rational b(4, 3);
    Rational c = a + b;
    bool equal = c == Rational(2, 1);
    if (!equal) {
      cout << "2/3 + 4/3 != 2" << endl;
      return 2;
    }
  }

  {
    Rational a(5, 7);
    Rational b(2, 9);
    Rational c = a - b;
    bool equal = c == Rational(31, 63);
    if (!equal) {
      cout << "5/7 - 2/9 != 31/63" << endl;
      return 3;
    }
  }
  {
    Rational a(2, 3);
    Rational b(4, 3);
    Rational c = a * b;
    bool equal = c == Rational(8, 9);
    if (!equal) {
      cout << "2/3 * 4/3 != 8/9" << endl;
      return 1;
    }
  }

  {
    Rational a(5, 4);
    Rational b(15, 8);
    Rational c = a / b;
    bool equal = c == Rational(2, 3);
    if (!equal) {
      cout << "5/4 / 15/8 != 2/3" << endl;
      return 2;
    }
  }

  {
    ostringstream output;
    output << Rational(-6, 8);
    if (output.str() != "-3/4") {
      cout << "Rational(-6, 8) should be written as \"-3/4\"" << endl;
      return 1;
    }
  }

  {
    istringstream input("5/7");
    Rational r;
    input >> r;
    bool equal = r == Rational(5, 7);
    if (!equal) {
      cout << "5/7 is incorrectly read as " << r << endl;
      return 2;
    }
  }

  {
    istringstream input("5/7 10/8");
    Rational r1, r2;
    input >> r1 >> r2;
    bool correct = r1 == Rational(5, 7) && r2 == Rational(5, 4);
    if (!correct) {
      cout << "Multiple values are read incorrectly: " << r1 << " " << r2 << endl;
      return 3;
    }

    input >> r1;
    input >> r2;
    correct = r1 == Rational(5, 7) && r2 == Rational(5, 4);
    if (!correct) {
      cout << "Read from empty stream shouldn't change arguments: " << r1 << " " << r2 << endl;
      return 4;
    }
  }

  {
    const set<Rational> rs = {{1, 2}, {1, 25}, {3, 4}, {3, 4}, {1, 2}};
    if (rs.size() != 3) {
      cout << "Wrong amount of items in the set" << endl;
      return 1;
    }

    vector<Rational> v;
    for (auto x : rs) {
      v.push_back(x);
    }
    if (v != vector<Rational>{{1, 25}, {1, 2}, {3, 4}}) {
      cout << "Rationals comparison works incorrectly" << endl;
      return 2;
    }
  }

  {
    map<Rational, int> count;
    ++count[{1, 2}];
    ++count[{1, 2}];

    ++count[{2, 3}];

    if (count.size() != 2) {
      cout << "Wrong amount of items in the map" << endl;
      return 3;
    }
  }

  cout << "OK" << endl;
  return 0;
}