Fraction class in C#

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• Download source code of Fraction class - 3.41 Kb
• Download an advanced version of Fraction class (updated by Marc Brooks & Jeffrey Sax) with test application - 13.8 Kb

Introduction

This article demonstrates how to remove the problem of limited precision when numbers such as 1/10, 1/7, 1/3, etc. are represented in a floating point variable type in C#. Yes, you guessed it right, this problem can be solved by storing such numbers in a fraction format. As a fraction object stores its numerator and denominator as integer variables, there is no loss of accuracy. For this purpose, I have written a simple C# class representing fractions. It can be used in various applications, e.g., equation solving, matrix transformations, etc.

Features of class

The class contains a variety of overloaded constructors and operators for certain situations. It also throws certain exceptions, e.g., when denominator is tried to assign a 0 value, when the result of an arithmetic exceeds the limit (range), etc. One more feature is the automatic normalization (simplification) of fractions. The class uses data type 'long integer' for storing numerator and denominator, hence its range is upper bounded by the range of Int64 in .NET framework.

Using the code

The class includes a variety of constructors, e.g., one that takes an integer like 123, one that takes a double like 156.25, one that takes a string that has all the above qualities (e.g., string can be "32/77" or "213" or "321.44"), one that takes values of numerator and denominator like 231 and 101, and, of course, a parameter-less constructor for a "zero" fraction stored as 0/1.

Fraction frac=new Fraction(); // we'll get 0/1

frac=new Fraction(1,5);       // we'll get 1/5

frac=new Fraction(25);        // we'll get 25/1

frac=new Fraction(9.25);      // we'll get 37/4

frac=new Fraction("6.25");    // we'll get 25/4


frac=new Fraction( System.Console.ReadLine() );
     // we can enter anything like "213" or 

     // "23/3" or "4.27"


Console.WriteLine( frac );
// displays the current value of frac1 object;

Operators overloaded (overloaded for fractions, integers and doubles) for Fraction object include:

• Unary: - (Negation)
• Binary +, -, *, /
• Relational operators such as ==, !=, <, >, <=, >=.

Fraction frac=new Fraction("1/2"); // initialize a fraction with 1/2

Console.WriteLine( frac+2.5 );     // will display 3

Overloaded conversion further enhances the capabilities of the class. See how simple it is to work with fractions:

Fraction frac="1/2" // implicit cast from string to 

frac="22.5"         // implicit cast from string to fraction

frac=10.25          // implicit cast from double to fraction

frac=15             // implicit cast from integer/long to fraction

Finally, as an exercise, guess the output of the following code:

Fraction f=0.5;                 // initialize frac=1/2

Console.WriteLine( f-0.25 );    // Yes, you are right. "1/4" is displayed

Console.WriteLine( f+"1/4" );
   // not sure??? It will display "3/4" because "1/4" has 

   // been converted to fraction and then added to our frac object

Implementation details

The class uses simple mathematics to do all the work. Let us see some of these simple techniques:

• To convert a double to a fraction, we keep multiplying the given double number with 10 until it is converted to an integer number.
• To convert a given string to a fraction, we treat all the value before "/" as numerator and after "/" as denominator.
• To normalize a fraction, we divide its numerator and denominator by their GCD (found by famous Euler's formula).
• To add two fractions, we use simple school formula to get numerator and denominator of the resultant fraction and then normalize it:

  Numerator = frac1.Numerator*frac2.Denominator 
              + frac2.Numerator*frac1.Denominator;
  Denominator = frac1.Denominator*frac2.Denominator;

• To overload arithmetic operators for integers and doubles, we first convert them to fractions and then perform the operation.

Applications

There are a lot of applications of Fraction class. An example is a matrix class, see my article on Matrix class in C#.

History

Version 2.0

• Changed Numerator and Denominator from Int32 (integer) to Int64 (long) for increased range.
• Renamed ConvertToString() to ToString().
• Added the capability of detecting/raising overflow exceptions.
• Fixed the bug that very small numbers, e.g. 0.00000001, could not be converted to fraction.
• Fixed other minor bugs.

Version 2.1

• Overloaded conversions from/to fractions.

Version 2.2 (changes by Marc Brooks and Jeffrey Sax).

• Less overflows by finding the GCD for Add [Jeffery Sax] and Multiply [Marc C. Brooks]
• Understands and handles NaN, PositiveInfinity, NegativeInfinity just like double [Marc C. Brooks]
• Fixed several uses of int where long was correct [Marc C. Brooks]
• Made value-type (struct) [Jeffery Sax]
• Added ToInt32(), ToInt64() which throw for invalid (NaN, PositiveInfinity, NegativeInfinity) [Marc C. Brooks]
• Removed redundant Value property [Jeffery Sax]
• Added explicit conversion to Int32 and Int64 [Marc C. Brooks]
• Better handling of exceptions [Marc C. Brooks]
• Reorganized code, added XML doc and regions [Marc C. Brooks]
• Proper implementations of Equals [Marc C. Brooks, Jeffery Sax]
• Uses Math.Log(xx,2) and Math.Pow(xx,2) to get the best accuracy possible when converting doubles [Marc C. Brooks, Jeffery Sax]

Version 2.3 (changes by Marc Brooks and Jeffrey Sax)

• Fixed double-to-fraction logic to use continued fraction rules to get best possible precision [bug fix for Syed Mehroz Alam, idea from Jeffery Sax]
• Added static readonly values for NaN, PositiveInfinity, NegativeInfinity [idea from Jeffery Sax]
• Moved comparisons into an implementation of IComparer [idea from Jeffery Sax]
• No longer throws for NaN(s) involved in Add, Subtract, Multiply, Divide operations [idea from Jeffery Sax]
• Added static readonly values for Zero, MinValue, MaxValue, Epsilon to better mirror double [Marc C. Brooks]
• Added IsInfinity to better mirror double [Marc C. Brooks]
• Added modulus and % operators [Marc C. Brooks]