Calculate Fractions in VB.NET

Scope

In this brief article we'll see a simple method to convert the decimal part of a number into its fractional representation, developing a reusable class to do it. To that end, we'll use Visual Basic .NET.

Calculate and simplify a fraction

To calculate a fraction, we must separate a number's integral part from the decimal one, to work on the latter to express it in terms of numerator and denominator. Let's take for example the number 12.65. We will first express it as 12 + 0.65, proceeding then in writing our decimal part as the most large non-simplified fraction. Since we have two decimals after the dot, the larger denominator we need is 100. So, we can express our 0.65 as 65/100. Then, using the common rules based on finding the Greatest Common Divisor (GDC), we can simplify our fraction, down to 13/20.

Finding the Greatest Common Divisor

The following is an easy snippet of code to help determine the GDC between two numbers:

Private Function gcd(ByVal n1 As Integer, ByVal n2 As Integer) As Long
Dim minimum As Long
If n1 < n2 Then
minimum = n1
Else
minimum = n2
End If
For i As Long = minimum To 1 Step -1
If n1 Mod i = 0 And n2 Mod i = 0 Then
Return i
End If
Next
End Function

Calculate a fraction

Here follows the routine that will calculate our fraction. It needs a decimal-type input parameter (as the 12.65 used previously).

Public Function Calculate(value As Decimal) As String
Dim intPart As Long = Math.Truncate(value)
Dim numerator As Long = CType((value - intPart).ToString.Substring(2), Long)
Dim denominator As Long = CType("1" & StrDup(numerator.ToString.Length, "0"), Long)
Dim _gcd As Long = gcd(numerator, denominator)
Dim nDiv As Long = _gcd
While nDiv > 1
If numerator Mod nDiv = 0 And denominator Mod nDiv = 0 Then
numerator /= nDiv
denominator /= nDiv
nDiv = _gcd
Else
nDiv -= 1
End If
End While
Dim retVal As String = ""
If intPart > 0 Then retVal = intPart.ToString & " + ("
retVal &= numerator.ToString + " / " + denominator.ToString
If intPart > 0 Then retVal &= ")"
Return retVal
End Function

The function will save the integral part of the number for later use, then proceed to calculate the maximum denominator, by adding a number of zeros to equal the number of decimal places. A call to our previously written GCD routine will compute the gretest Common Divisor between our numerator and denominator, entering a loop for dividing the numerator and denominator to determine their common divisors, until no common divisor is available.

Finally, having determined the simplyfied numerator and denominator, the routine will produce their string representation, joining the integral part. So, for our previous example of value = 12.65, the output will be: 12 + (13/20).

As the reader can note, in case no integral part is present, the fraction will be expressed without parenthesis.

Fraction class

The complete source for a reusable class can be the following:

Public Class Fraction
Dim _value As Decimal
Dim _fraction As String
Public ReadOnly Property Value As String
Get
Return _fraction
End Get
End Property
Public Property Number As Decimal
Get
Return _value
End Get
Set(value As Decimal)
_value = value
_fraction = Calculate(_value)
End Set
End Property
Public Sub New(value As Decimal)
_value = value
_fraction = Calculate(_value)
End Sub
Public Sub New()
_value = 0
_fraction = 0
End Sub
Private Function gcd(ByVal n1 As Integer, ByVal n2 As Integer) As Long
Dim minimum As Long
If n1 < n2 Then
minimum = n1
Else
minimum = n2
End If
For i As Long = minimum To 1 Step -1
If n1 Mod i = 0 And n2 Mod i = 0 Then
Return i
End If
Next
End Function
Public Function Calculate(value As Decimal) As String
Dim intPart As Long = Math.Truncate(value)
Dim numerator As Long = CType((value - intPart).ToString.Substring(2), Long)
Dim denominator As Long = CType("1" & StrDup(numerator.ToString.Length, "0"), Long)
Dim _gcd As Long = gcd(numerator, denominator)
Dim nDiv As Long = _gcd
While nDiv > 1
If numerator Mod nDiv = 0 And denominator Mod nDiv = 0 Then
numerator /= nDiv
denominator /= nDiv
nDiv = _gcd
Else
nDiv -= 1
End If
End While
Dim retVal As String = ""
If intPart > 0 Then retVal = intPart.ToString & " + ("
retVal &= numerator.ToString + " / " + denominator.ToString
If intPart > 0 Then retVal &= ")"
Return retVal
End Function
End Class

In the source code that comes with that article, I've implemented a simple Windows Forms form, with a TextBox and some Labels, to show how the previous code works.

The code behind will be as simple as this:

Public Class Form1
Dim f As New Fraction
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
f.Number = CType(TextBox1.Text, Decimal)
Label3.Text = f.Value
End Sub
End Class

When the Button is clicked, the Number property of our Fraction class will be initialized with a cast towards Decimal type of what is contained in TextBox1.

Next, the property Value (that will contain our fraction string) will be shown in Label3.

Source Code

The sample code for this article can be downloaded from this link.

8 Comments

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Gopi Chand11y ago
Good one
Santhakumar Munuswamy11y ago
Thanks for Nice article
Sibeesh Venu11y ago
Nice Share
Rajeesh Menoth11y ago
Thanks for sharing sir
Saineshwar Bageri11y ago
Good one sir try these thing in C# now VB.net is also coming to end
Gowtham K11y ago
Good one
Karthikeyan K11y ago
Thanks for share...
Rakesh11y ago
Good One