📄 fraction.cpp.html

📁 《Big C++ 》Third Edition电子书和代码全集-Part1
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<pre>  1  #include "fraction.h"
  2  #include &lt;cassert&gt;
  3  #include &lt;stdexcept&gt;
  4  
  5  int Fraction::gcd(int n, int m)
  6  {
  7     // Euclid's Greatest Common Divisor algorithm.
  8     assert((n &gt; 0) && (m &gt; 0));
  9     while (n != m)
 10     {
 11        if (n &lt; m)
 12           m = m - n;
 13        else
 14           n = n - m;
 15     }
 16     return n;
 17  }
 18  
 19  Fraction::Fraction(int t, int b) : top(t), bottom(b)
 20  {
 21     normalize();
 22  }
 23  
 24  Fraction::Fraction() : top(0), bottom(1) {}
 25  
 26  Fraction::Fraction(int t) : top(t), bottom(1) {}
 27  
 28  int Fraction::numerator() const
 29  {
 30     return top;
 31  }
 32  
 33  int Fraction::denominator() const
 34  {
 35     return bottom;
 36  }
 37  
 38  void Fraction::normalize()
 39  {
 40     // Normalize fraction by
 41     // (a) moving sign to numerator
 42     // (b) ensuring numerator and denominator have no common divisors
 43     int sign = 1;
 44     if (top &lt; 0)
 45     {
 46        sign = -1;
 47        top = -top;
 48     }
 49     if (bottom &lt; 0)
 50     {
 51        sign = -sign;
 52        bottom = -bottom;
 53     }
 54     assert(bottom != 0)
 55     int d = 1;
 56     if (top &gt; 0) d = gcd(top, bottom);
 57     top = sign * (top / d);
 58     bottom = bottom / d;
 59  } 
 60  
 61  Fraction operator+(const Fraction& left, const Fraction& right)
 62  {
 63     Fraction result(left.numerator() * right.denominator()
 64        + right.numerator() * left.denominator(),
 65        left.denominator() * right.denominator());
 66     return result;
 67  }
 68  
 69  Fraction operator-(const Fraction& left, const Fraction& right)
 70  {
 71     Fraction result(left.numerator() * right.denominator()
 72        - right.numerator() * left.denominator(),
 73        left.denominator() * right.denominator());
 74     return result;
 75  }
 76  
 77  Fraction operator*(const Fraction& left, const Fraction& right)
 78  {
 79     Fraction result(left.numerator() * right.numerator(),
 80        left.denominator() * right.denominator());
 81     return result;
 82  }
 83  
 84  Fraction operator/(const Fraction& left, const Fraction& right)
 85  {
 86     Fraction result(left.numerator() * right.denominator(),
 87        left.denominator() * right.numerator());
 88     return result;
 89  }
 90  
 91  Fraction operator-(const Fraction& value)
 92  {
 93     Fraction result(-value.numerator(), value.denominator());
 94     return result;
 95  }
 96  
 97  int Fraction::compare(const Fraction& right) const
 98  {
 99     return numerator() * right.denominator()
100     - denominator() * right.numerator();
101     // Return the numerator of the difference
102  }
103  
104  bool operator&lt;(const Fraction& left, const Fraction& right)
105  {
106     return left.compare(right) &lt; 0;
107  }
108  
109  bool operator&lt;=(const Fraction& left, const Fraction& right)
110  {
111     return left.compare(right) &lt;= 0;
112  }
113  
114  bool operator==(const Fraction& left, const Fraction& right)
115  {
116     return left.compare(right) == 0;
117  }
118  
119  bool operator!=(const Fraction& left, const Fraction& right)
120  {
121     return left.compare(right) != 0;
122  }
123  
124  bool operator&gt;=(const Fraction& left, const Fraction& right)
125  {
126     return left.compare(right) &gt;= 0;
127  }
128  
129  bool operator&gt;(const Fraction& left, const Fraction& right)
130  {
131     return left.compare(right) &gt; 0;
132  }
133  
134  ostream& operator&lt;&lt;(ostream& out, const Fraction& value)
135  {
136     out &lt;&lt; value.numerator() &lt;&lt; "/" &lt;&lt; value.denominator();
137     return out;
138  }
139  
140  istream& operator&gt;&gt;(istream& in, Fraction& r)
141  {
142     int t, b;
143     // Read the top
144     in &gt;&gt; t;
145     // If there is a slash, read the next number
146     char c;
147     in &gt;&gt; c;
148     if (c == '/')
149        in &gt;&gt; b;
150     else
151     {
152        in.putback(c);
153        b = 1;
154     }
155     r = Fraction(t, b);
156     return in;
157  }
158  
159  Fraction::operator double() const
160  {
161     // Convert numerator to double, then divide
162     return static_cast&lt;double&gt;(top) / bottom;
163  }
164  
165  Fraction& Fraction::operator++()
166  {
167     top += bottom;
168     return *this;
169  }
170  
171  Fraction Fraction::operator++(int unused)
172  {
173     Fraction clone(top, bottom);
174     top += bottom;
175     return clone;
176  }
177  
178  Fraction& Fraction::operator+=(const Fraction& right)
179  {
180     top = top * right.denominator() + bottom * right.numerator();
181     bottom *= right.denominator();
182     normalize();
183     return *this;
184  }</pre>
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