[AccessD] "fuzzy logic" search

On 21 Oct 2003 at 22:58, MartyConnelly wrote:

> Why not use a weighted checksum like the ISBN number, it will also 
> indicated the position of a single substitution error and I think the 
> location of a single transposition error.
> 

Too many potential false matches 

Combining HammingDistance with a straight Checksum seems to work 
quite well though. Here's what I've come up with to test for a single 
miskey or a transposition error:

Function HammingDistance(BaseString As String, TestString As String) As Long
Dim lngHamCount As Long
Dim lngLen As Long
lngLen = Len(BaseString)
If Len(TestString) <> lngLen Then
    HammingDistance = -1
    Exit Function
Else
  For loopcount = 1 To lngLen
     If Mid$(BaseString, loopcount, 1) <> Mid$(TestString, loopcount, 1) Then
        lngHamCount = lngHamCount + 1
     End If
  Next
End If
HammingDistance = lngHamCount
End Function

Function CheckSum(TestString) As Long
Dim lngCheck As Long
For loopcount = 1 To Len(BaseString)
   lngCheck = lngCheck + Asc(Mid$(TestString, loopcount, 1))
Next
End Function

Function PossibleMatch(BaseString As String, TestString As String) As Boolean
Select Case HammingDistance(BaseString, TestString)
    Case 1 ' Miskey?
       PossibleMatch = True
    Case 2  'Possible transposition?
       If CheckSum(BaseString) = CheckSum(TestString) Then
           PossibleMatch = True
       End If
    Case Else
       PossibleMatch = False
End Select
End Function 
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