Working with BIG numbers or LOTS of decimal places

[killo]

Public Function subtract(tnum1 As String, tnum2 As String) As String
Dim i As Long
Dim length As Long
Dim temp As Integer
Dim carry As Byte
Dim num1 As String
Dim num2 As String
num1 = tnum1
num2 = tnum2
checkdec:
'format like always
If InStr(num1, ".") > 0 And InStr(num2, ".") > 0 Then
    If (Len(num1) - InStr(num1, ".")) < (Len(num2) - InStr(num2, ".")) Then
        Do
            num1 = num1 & "0"
        Loop Until (Len(num1) - InStr(num1, ".")) = (Len(num2) - InStr(num2, "."))
    ElseIf (Len(num1) - InStr(num1, ".")) > (Len(num2) - InStr(num2, ".")) Then
        Do
            num2 = num2 & "0"
        Loop Until (Len(num1) - InStr(num1, ".")) = (Len(num2) - InStr(num2, "."))
    End If
ElseIf InStr(num1, ".") > 0 And InStr(num2, ".") = 0 Then
    num2 = num2 & "."
    GoTo checkdec
ElseIf InStr(num1, ".") = 0 And InStr(num2, ".") > 0 Then
    num1 = num1 & "."
    GoTo checkdec
End If

If Len(num1) > Len(num2) Then
    length = Len(num1)
    num2 = String$(length - Len(num2), "0") & num2
ElseIf Len(num2) > Len(num1) Then
    length = Len(num2)
    num1 = String$(length - Len(num1), "0") & num1
Else
    length = Len(num1)
End If

'subtract the numbers in a similar way to the add code
carry = 0
For i = 1 To length
    If Mid(num1, (length - i + 1), 1) = "." Then
        subtract = "." & subtract
    Else
        temp = Val(Mid(num1, (length - i + 1), 1)) - Val(Mid(num2, (length - i + 1), 1)) - carry
        If temp >= 0 Then
            subtract = temp & subtract
            carry = 0
        ElseIf temp < 0 Then
            carry = 1
            temp = temp + 10
            If temp < 0 Then
                temp = temp + 10
                carry = 2
            End If
            subtract = temp & subtract
        End If
    End If

Next i

Do While Left(subtract, 1) = "0"
 subtract = Right(subtract, Len(subtract) - 1)
Loop

If Left(subtract, 1) = "." Then subtract = "0" & subtract



End Function






Public Function multiply(tnum1 As String, tnum2 As String) As String
Dim num1 As String
Dim num2 As String


Dim tempnum3 As String
Dim mcounter As String
Dim tempnum2 As String
Dim templeft As String
Dim tempright As String
Dim tempnum1 As String

If morethan(tnum1, tnum2) Then
    num2 = tnum1
    num1 = tnum2
Else
num1 = tnum1
num2 = tnum2
End If

If InStr(num2, ".") > 0 Then
    If Left(num2, 2) = "0." Then
        'extract 38 and 0.45 from 38.45 for example
        tempnum2 = num2
        num2 = 0
    Else
    tempnum2 = "0." & Right(num2, (Len(num2) - InStr(num2, ".")))
    num2 = Left(num2, (InStr(num2, ".")) - 1)
End If
tempnum1 = num1

'once they have been extracted, the decimal places need to be moved
'turn 6.42 * 0.34 into 34 * 0.0642 for example
'this will give the same result, but the multiplication code needs at least one of the numbers to be whole for it to work
'so that is why this needs to be done
If InStr(tempnum1, ".") = 0 Then tempnum1 = tempnum1 & "."
    Do
        templeft = Left(tempnum1, (InStr(tempnum1, ".") - 1))
        tempright = Right(tempnum1, (Len(tempnum1) - (InStr(tempnum1, "."))))
        If Len(templeft) = 1 Then templeft = 0 & templeft
        tempright = Right(templeft, 1) & tempright
        templeft = Left(templeft, Len(templeft) - 1)
        tempnum1 = templeft & "." & tempright
        templeft = Left(tempnum2, (InStr(tempnum2, ".") - 1))
        tempright = Right(tempnum2, (Len(tempnum2) - (InStr(tempnum2, "."))))
        templeft = templeft & Left(tempright, 1)
        tempright = Right(tempright, Len(tempright) - 1)
        tempnum2 = templeft & "." & tempright
    Loop Until Right(tempnum2, 1) = "."
    tempnum2 = Left(tempnum2, Len(tempnum2) - 1)
    Do While Left(tempnum2, 1) = "0"
        tempnum2 = Right(tempnum2, Len(tempnum2) - 1)
    Loop

'multiply just the 0.?? for now
    Do Until mcounter = tempnum2
        multiply = add(multiply, tempnum1)
        mcounter = add(mcounter, 1)
DoEvents
    Loop
End If

'swap the numbers if one is bigger than the other so that the multiplication code doesn't need to loop around so much
If morethan(num2, num1) And InStr(num1, ".") = 0 Then
    tempnum3 = num1
    num1 = num2
    num2 = tempnum3
End If
'multiply the whole numbers
mcounter = 0
Do Until mcounter = num2
    multiply = add(multiply, num1)
    mcounter = add(mcounter, 1)
Loop

'remove any unnecessary 0's at the right if there is a decimal place
If InStr(multiply, ".") > 0 Then
    Do While Right(multiply, 1) = "0"
         multiply = Left(multiply, Len(multiply) - 1)
    Loop
End If

'remove any unnecessary 0's at the left

Do While Left(multiply, 1) = "0"
    multiply = Right(multiply, Len(multiply) - 1)
Loop

If Left(multiply, 1) = "." Then multiply = "0" & multiply

End Function


Public Function power(tnum1 As String, tnum2 As String) As String
Dim pcounter As Long
Dim num1 As String
Dim num2 As String
num1 = tnum1
num2 = tnum2
power = 1

Do
    'multiply the number by itself the necessary amount of times
    power = multiply(power, num1)
    pcounter = pcounter + 1

Loop Until pcounter = num2

End Function