Dug this up from some old code. I think Luc was working with me on this for a Fraction class a long time ago. Here's an excerpt for dealing with fraction reduction:
Private Shared ReadOnly Primes As Decimal() = {3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97}
Public Shared Sub ReduceByGcd(ByRef fractionNumerator As Integer, ByRef fractionDenominator As Integer)
Dim gdc As Integer = GetGreatestCommonDivisor(fractionNumerator, fractionDenominator)
If gdc = 1 Then
Dim mantissa As Decimal = CDec(System.Math.Abs(fractionNumerator / fractionDenominator))
For Each prime As Decimal In Primes
Dim theta As Decimal = 1D / prime
If (mantissa / theta) Mod 1D > 0.99 Then
Dim deltaN As Integer = CInt(Decimal.Ceiling(CDec(fractionNumerator / fractionDenominator / theta)))
Dim deltaD As Integer = CInt(prime)
If deltaN = deltaD Then deltaN = 1 : deltaD = 1
fractionNumerator = deltaN
fractionDenominator = deltaD
Exit Sub
End If
Next
ElseIf gdc > 1 Then
fractionNumerator = CInt(Decimal.Ceiling(CDec(fractionNumerator / gdc)))
fractionDenominator = CInt(Decimal.Ceiling(CDec(fractionDenominator / gdc)))
End If
End Sub
Public Shared Function GetGreatestCommonDivisor(number1 As Integer, number2 As Integer) As Integer
number1 = System.Math.Abs(number1)
number2 = System.Math.Abs(number2)
Dim delta As Integer
If number1 > number2 Then
delta = number1
number1 = number2
number2 = delta
End If
While number1 > 0
delta = number2 Mod number1
number2 = number1
number1 = delta
End While
Return number2
End Function
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
Dim parts() As String = TextBox2.Text.Split("/"c)
Dim numer As Integer = Integer.Parse(parts(0))
Dim denom As Integer = Integer.Parse(parts(1))
ReduceByGcd(numer, denom)
TextBox2.Text = $"{numer}/{denom}"
End Sub
Reed Kimble - "When you do things right, people won't be sure you've done anything at all"
