rational.h

/*  Rational - Rational number class with overflow detection
    Copyright (C) 2005-2019 Antonio Diaz Diaz.

    This library is free software. Redistribution and use in source and
    binary forms, with or without modification, are permitted provided
    that the following conditions are met:

    1. Redistributions of source code must retain the above copyright
    notice, this list of conditions, and the following disclaimer.

    2. Redistributions in binary form must reproduce the above copyright
    notice, this list of conditions, and the following disclaimer in the
    documentation and/or other materials provided with the distribution.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
*/

// Rationals are kept normalized at all times.
// Invariant = ( gcd( num, den ) == 1 && den > 0 ).
// Range extends from INT_MAX to -INT_MAX.
// Maximum resolution is 1 / INT_MAX.
// In case of domain error or overflow, den is set to 0 and num is set
// to >0, <0, or 0, meaning +INF, -INF, and NAN respectively. This error
// condition can be tested with the 'error' function, and can only be
// cleared assigning a new value to the Rational.
// While in error state, arithmetic operators become no ops and
// relational operators return false, except !=, which returns true.
//
class Rational
  {
  int num, den;

  void normalize( long long n, long long d );
  void normalize();

public:
  Rational( const int n, const int d ) : num( n ), den( d )	// n / d
    { normalize(); }
  explicit Rational( const int n ) : num( n ), den( 1 )		// n / 1
    { if( num < -INT_MAX ) { num = -INT_MAX; den = 0; } }
  Rational() : num( 0 ), den( 1 ) {}				// zero

  Rational & assign( const int n, const int d )
    { num = n; den = d; normalize(); return *this; }
  Rational & operator=( const int n )
    { num = n; den = 1; if( num < -INT_MAX ) { num = -INT_MAX; den = 0; }
      return *this; }

  int numerator() const { return num; }
  int denominator() const { return den; }
  int sign() const
    { if( num > 0 ) return 1; if( num < 0 ) return -1; return 0; }
  bool error() const { return ( den <= 0 ); }	// true if in error state

  const Rational & operator+() const { return *this; }	// unary plus const
  Rational & operator+() { return *this; }		// unary plus
  Rational operator-() const				// unary minus
    { Rational tmp( *this ); tmp.num = -tmp.num; return tmp; }

  Rational abs() const { if( num >= 0 ) return *this; else return -*this; }
  Rational inverse() const;

  Rational & operator+=( const Rational & r );
  Rational & operator-=( const Rational & r ) { return operator+=( -r ); }
  Rational & operator*=( const Rational & r );
  Rational & operator/=( const Rational & r )
    { return operator*=( r.inverse() ); }

  Rational & operator+=( const int n ) { return operator+=( Rational( n ) ); }
  Rational & operator-=( const int n ) { return operator-=( Rational( n ) ); }
  Rational & operator*=( const int n ) { return operator*=( Rational( n ) ); }
  Rational & operator/=( const int n ) { return operator/=( Rational( n ) ); }

  Rational operator+( const Rational & r ) const
    { Rational tmp( *this ); return tmp += r; }
  Rational operator-( const Rational & r ) const
    { Rational tmp( *this ); return tmp -= r; }
  Rational operator*( const Rational & r ) const
    { Rational tmp( *this ); return tmp *= r; }
  Rational operator/( const Rational & r ) const
    { Rational tmp( *this ); return tmp /= r; }

  Rational operator+( const int n ) const
    { Rational tmp( *this ); return tmp += n; }
  Rational operator-( const int n ) const
    { Rational tmp( *this ); return tmp -= n; }
  Rational operator*( const int n ) const
    { Rational tmp( *this ); return tmp *= n; }
  Rational operator/( const int n ) const
    { Rational tmp( *this ); return tmp /= n; }

  Rational & operator++() { return operator+=( 1 ); }		// prefix
  Rational operator++( int )					// suffix
    { Rational tmp( *this ); operator+=( 1 ); return tmp; }
  Rational & operator--() { return operator-=( 1 ); }		// prefix
  Rational operator--( int )					// suffix
    { Rational tmp( *this ); operator-=( 1 ); return tmp; }

  bool operator==( const Rational & r ) const
    { return ( den > 0 && num == r.num && den == r.den ); }
  bool operator==( const int n ) const
    { return ( num == n && den == 1 ); }
  bool operator!=( const Rational & r ) const
    { return ( den <= 0 || r.den <= 0 || num != r.num || den != r.den ); }
  bool operator!=( const int n ) const
    { return ( num != n || den != 1 ); }

  bool operator< ( const Rational & r ) const
    { return ( den > 0 && r.den > 0 &&
               (long long)num * r.den < (long long)r.num * den ); }
  bool operator<=( const Rational & r ) const
    { return ( den > 0 && r.den > 0 &&
               (long long)num * r.den <= (long long)r.num * den ); }
  bool operator> ( const Rational & r ) const
    { return ( den > 0 && r.den > 0 &&
               (long long)num * r.den > (long long)r.num * den ); }
  bool operator>=( const Rational & r ) const
    { return ( den > 0 && r.den > 0 &&
               (long long)num * r.den >= (long long)r.num * den ); }

  bool operator< ( const int n ) const { return operator< ( Rational( n ) ); }
  bool operator<=( const int n ) const { return operator<=( Rational( n ) ); }
  bool operator> ( const int n ) const { return operator> ( Rational( n ) ); }
  bool operator>=( const int n ) const { return operator>=( Rational( n ) ); }

  int round() const;		// nearest integer; -1.5 ==> -2,  1.5 ==> 2
  int trunc() const		// integer part;    -x.y ==> -x,  x.y ==> x
    { if( den > 0 ) return ( num / den ); else return num; }

  int parse( const char * const s );		// returns parsed size
  std::string to_decimal( const unsigned iwidth = 1, int prec = -2 ) const;
  std::string to_fraction( const unsigned width = 1 ) const;
  };


inline Rational operator+( const int n, const Rational & r ) { return r + n; }
inline Rational operator-( const int n, const Rational & r ) { return -r + n; }
inline Rational operator*( const int n, const Rational & r ) { return r * n; }
inline Rational operator/( const int n, const Rational & r )
  { return Rational( n ) / r; }

inline bool operator==( const int n, const Rational & r ) { return r == n; }
inline bool operator!=( const int n, const Rational & r ) { return r != n; }

inline bool operator< ( const int n, const Rational & r ) { return r >  n; }
inline bool operator<=( const int n, const Rational & r ) { return r >= n; }
inline bool operator> ( const int n, const Rational & r ) { return r <  n; }
inline bool operator>=( const int n, const Rational & r ) { return r <= n; }