fraction.h

《Big C++ 》Third Edition电子书和代码全集-Part1

#ifndef FRACTION_H
#define FRACTION_H

#include <iostream>

using namespace std;

class Fraction {
public:
   /**
      Constructs a fraction with numerator 0 and denominator 1
   */
   Fraction();

   /**
      Constructs a fraction with numerator t and denominator 1
      @param t the numerator for the fraction
   */
   Fraction(int t);

   /**
      Constructs a fraction with given numerator and denominator
      @param t the initial numerator
      @param b the initial denominator
   */
   Fraction(int t, int b);

   /**
      Returns the numerator 
      @return the numerator value
   */
   int numerator() const;

   /**
      Returns the denominator
      @return the denominator value
   */
   int denominator() const;

   /**
      updates a fraction by adding in another fraction value
      @param right  the fraction to be added
      @ return the updated fraction value
   */
   Fraction& operator+=(const Fraction& right);

   /**
     increment  fraction by 1
   */
   Fraction& operator++(); // Prefix form
   Fraction operator++(int unused); // Postfix form

   /**
      converts a fraction into a floating-point value
      @return the converted value
   */
   operator double() const;

   /**
      compare one fraction value to another
      result is negative if less than right, zero if equal, and 
      positive if greater than right
      @param right the fraction to be compared against 
   */
   int compare(const Fraction& right) const;
private:
   /**
      place the fraction in least common denominator form
   */
   void normalize();
   /**
      compute the greatest common denominator of two integer values
      @param n the first integer
      @param m the second integer
   */
   int gcd(int n, int m);
   int top;
   int bottom;
};

Fraction operator+(const Fraction& left, const Fraction& right);
Fraction operator-(const Fraction& left, const Fraction& right);
Fraction operator*(const Fraction& left, const Fraction& right);
Fraction operator/(const Fraction& left, const Fraction& right);
Fraction operator-(const Fraction& value);

bool operator<(const Fraction& left, const Fraction& right);
bool operator<=(const Fraction& left, const Fraction& right);
bool operator==(const Fraction& left, const Fraction& right);
bool operator!=(const Fraction& left, const Fraction& right);
bool operator>=(const Fraction& left, const Fraction& right);
bool operator>(const Fraction& left, const Fraction& right);

ostream& operator<<(ostream& out, const Fraction& value);
istream& operator>>(istream& in, Fraction& r);

#endif