Logic error
In computer programming, a logic error is a bug in a program that causes it to operate incorrectly, but not to terminate abnormally (or crash). A logic error produces unintended or undesired output or other behaviour, although it may not immediately be recognized as such.
Logic errors occur in both compiled and interpreted languages. Unlike a program with a syntax error, a program with a logic error is a valid program in the language, though it does not behave as intended. Often the only clue to the existence of logic errors is the production of wrong solutions, though static analysis may sometimes spot them.
Debugging logic errors
One of the ways to find this type of error is to output the program's variables to a file or on the screen in order to determine the error's location in code. Although this will not work in all cases, for example when calling the wrong subroutine, it is the easiest way to find the problem if the program uses the incorrect results of a bad mathematical calculation.
Option Explicit
'Main Function
Function SpellNumber(ByVal MyNumber)
Dim Dollars, Cents, Temp
Dim DecimalPlace, Count
ReDim Place(9) As String
Place(2) = " Thousand "
Place(3) = " Million "
Place(4) = " Billion "
Place(5) = " Trillion "
' String representation of amount.
MyNumber = Trim(Str(MyNumber))
' Position of decimal place 0 if none.
DecimalPlace = InStr(MyNumber, ".")
' Convert cents and set MyNumber to dollar amount.
If DecimalPlace > 0 Then
Cents = GetTens(Left(Mid(MyNumber, DecimalPlace + 1) & _ "00", 2))
MyNumber = Trim(Left(MyNumber, DecimalPlace - 1))
End If
Count = 1
Do While MyNumber <> ""
Temp = GetHundreds(Right(MyNumber, 3))
If Temp <> "" Then Dollars = Temp & Place(Count) & Dollars
If Len(MyNumber) > 3 Then
MyNumber = Left(MyNumber, Len(MyNumber) - 3)
Else
MyNumber = ""
End If
Count = Count + 1
Loop
Select Case Dollars
Case ""
Dollars = "No Dollars"
Case "One"
Dollars = "One Dollar"
Case Else
Dollars = Dollars & " Dollars"
End Select
Select Case Cents
Case ""
Cents = " and No Cents"
Case "One"
Cents = " and One Cent"
Case Else
Cents = " and " & Cents & " Cents"
End Select
SpellNumber = Dollars & Cents
End Function
' Converts a number from 100-999 into text
Function GetHundreds(ByVal MyNumber)
Dim Result As String
If Val(MyNumber) = 0 Then Exit Function
MyNumber = Right("000" & MyNumber, 3)
' Convert the hundreds place.
If Mid(MyNumber, 1, 1) <> "0" Then
Result = GetDigit(Mid(MyNumber, 1, 1)) & " Hundred "
End If
' Convert the tens and ones place.
If Mid(MyNumber, 2, 1) <> "0" Then
Result = Result & GetTens(Mid(MyNumber, 2))
Else
Result = Result & GetDigit(Mid(MyNumber, 3))
End If
GetHundreds = Result
End Function
' Converts a number from 10 to 99 into text.
Function GetTens(TensText)
Dim Result As String
Result = "" ' Null out the temporary function value.
If Val(Left(TensText, 1)) = 1 Then ' If value between 10-19...
Select Case Val(TensText)
Case 10: Result = "Ten"
Case 11: Result = "Eleven"
Case 12: Result = "Twelve"
Case 13: Result = "Thirteen"
Case 14: Result = "Fourteen"
Case 15: Result = "Fifteen"
Case 16: Result = "Sixteen"
Case 17: Result = "Seventeen"
Case 18: Result = "Eighteen"
Case 19: Result = "Nineteen"
Case Else
End Select
Else ' If value between 20-99...
Select Case Val(Left(TensText, 1))
Case 2: Result = "Twenty "
Case 3: Result = "Thirty "
Case 4: Result = "Forty "
Case 5: Result = "Fifty "
Case 6: Result = "Sixty "
Case 7: Result = "Seventy "
Case 8: Result = "Eighty "
Case 9: Result = "Ninety "
Case Else
End Select
Result = Result & GetDigit _
(Right(TensText, 1)) ' Retrieve ones place.
End If
GetTens = Result
End Function
' Converts a number from 1 to 9 into text.
Function GetDigit(Digit)
Select Case Val(Digit)
Case 1: GetDigit = "One"
Case 2: GetDigit = "Two"
Case 3: GetDigit = "Three"
Case 4: GetDigit = "Four"
Case 5: GetDigit = "Five"
Case 6: GetDigit = "Six"
Case 7: GetDigit = "Seven"
Case 8: GetDigit = "Eight"
Case 9: GetDigit = "Nine"
Case Else: GetDigit = ""
End Select
End Function
See also
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