Number to text

[minitech]

This is my first cool project in a while Everybody always makes numbers-to-text functions some time, but this one goes up to sextillions (and could handle much more than that), has proper grammar, and does irreductible fractions for you!

Public Function ToWords(ByVal num As Decimal) As String
        If num = 0 Then Return "Zero"

        Dim illions() As String = {"m", "b", "tr", "quadr", "quint", "sext"} ', "sept", "oct", "non", "dec", "undec", "dodec"} 'Go farther if you want... but you'll have to change the numerical type.
        Dim ties() As String = {"twen", "thir", "four", "fif", "six", "seven", "eight", "nine"}
        Dim nums() As String = {"one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten"}
        Dim teens() As String = {"eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen"}
        Dim result As New System.Text.StringBuilder()

        If num < 0 Then
            result.Append("negative ")
            num = -num
        End If

        '***illions first...
        For i As Integer = illions.Length - 1 To 0 Step -1
            'They always come in threes, starting with 1000000.
            Dim d As Decimal = 1000
            For x As Integer = 0 To i
                d *= 1000
            Next

            Dim n As Integer = 0
            While num >= d
                n += 1
                num -= d
            End While

            If n > 0 Then
                result.Append(ToWords(n))
                result.Append(" "c)
                result.Append(illions(i))
                result.Append("illion, ")
            End If
        Next

        'Then, thousands
        Dim thousands As Integer = 0
        While num >= 1000
            thousands += 1
            num -= 1000
        End While

        If thousands > 0 Then
            result.Append(ToWords(thousands))
            result.Append(" thousand, ")
        End If

        'Hundreds
        Dim hundreds As Integer = 0
        While num >= 100
            hundreds += 1
            num -= 100
        End While

        If hundreds > 0 Then
            result.Append(ToWords(hundreds))
            result.Append(" hundred ")
        End If

        'Tens
        If num >= 20 Then
            result.Append(ties(CInt(Math.Floor(num / 10)) - 2))
            result.Append("ty-")
            num -= CInt(Math.Floor(num / 10)) * 10
        End If

        If num < 20 AndAlso num > 10 Then
            result.Append(teens(CInt(Math.Floor(num - 10)) - 1))
            result.Append(" "c)
            num -= 10
        End If

        'Singles
        If Math.Floor(num) > 0 Then
            result.Append(nums(CInt(Math.Floor(num)) - 1))
            result.Append(" "c)
            num -= Math.Floor(num)
        End If

        'Now, the hard part - fractions.
        If num > 0 Then
            Dim numerator, denominator As Integer
            If ToFraction(num, numerator, denominator) Then
                result.Append("and ")
                result.Append(ToWords(numerator))
                result.Append(" "c)

                Dim ths() As String = {"half", "third", "fourth", "fifth"}
                Dim thp() As String = {"halves", "thirds", "fourths", "fifths"}

                If denominator <= ths.Length + 1 Then
                    result.Append(If(numerator = 1, ths(denominator - 2), thp(denominator - 2)))
                    result.Append(" "c)
                Else
                    result.Append(ToWords(denominator).Replace(" "c, "-"c)) 'Fourty-millionths, not fourty millionths.
                    result.Append("th")
                    If numerator > 1 Then result.Append("s"c)
                    result.Append(" "c)
                End If
            Else
                result.Append("point ")
                Do
                    num *= 10
                    result.Append(ToWords(Math.Floor(num)))
                    result.Append(" "c)
                    num -= Math.Floor(num)
                Loop While num > 0
            End If
        End If

        'Some final processing
        result.Remove(result.Length - 1, 1)
        If result(result.Length - 1) = ","c Then result.Remove(result.Length - 1, 1)

        'Return the result
        ToWords = result.ToString().ToLower()
        ToWords = Char.ToUpper(ToWords.Chars(0)) & ToWords.Substring(1)
    End Function

    Public Function ToFraction(ByVal n As Decimal, ByRef numerator As Integer, ByRef denominator As Integer) As Boolean
        Try
            'We don't support 0.333333333333 = 1/3, unfortunately. :(
            numerator = Integer.Parse(n.ToString().Substring(2))
            denominator = CInt(10 ^ (n.ToString().Length - 2))
            Dim tN As Integer = numerator
            Dim tD As Integer = denominator

            Dim nFactors As New List(Of Integer)
            Dim dFactors As New List(Of Integer)
            For d As Integer = 2 To numerator - 1
                While tN Mod d = 0
                    nFactors.Add(d)
                    tN \= d
                End While
            Next
            If nFactors.Count = 0 Then nFactors.Add(numerator)

            For d As Integer = 2 To denominator - 1
                While tD Mod d = 0
                    dFactors.Add(d)
                    tD \= d
                End While
            Next
            If dFactors.Count = 0 Then dFactors.Add(denominator)

            Dim i As Integer
            While i < nFactors.Count
                Dim j As Integer = dFactors.IndexOf(nFactors(i))
                If j > -1 Then
                    dFactors.RemoveAt(j)
                    nFactors.RemoveAt(i)
                Else
                    i += 1
                End If
            End While

            numerator = nFactors.Aggregate(Function(m As Integer, o As Integer) m * o)
            denominator = dFactors.Aggregate(Function(m As Integer, o As Integer) m * o)

            Return True
        Catch
            Return False
        End Try
    End Function