Script Engine - VB.NET Based

Quote:

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Originally Posted by TheBarret

Was not about hurting feelings more about manors.

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I don't get it? What's been wrong with my manor? I have done nothing but trying to help you in this thread and when I mentioned that I have a hard time following spaghetti code which GOTO's lead to, you took that as an insult. It was not meant as such, I just want you to understand good coding practices.

Over to your code:

If you're still talking about how to avoid Goto statements, then this is one way of doing it:

Code:

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Private Function CheckForVar(strline As String) As String
    ' Changed the name of all local variables to be
    ' camelCased instead of PascalCased (leading lower case character)
    Dim tmpLine As String = strline
    Dim currentChar As String = ""
    Dim varName As String = ""
    Dim varValue As String = ""
    Dim pos As Integer = 0
    Dim posT As Integer = Len(strline)
    Dim check As Boolean = False
    Dim done As Boolean = False ' <-- I added this

    Do  ' <-- Replaced your Label with a Do loop
        For i = 0 To PosT - 1 ' <-- Change the For loop so it loops from 0. This is for SubString to work correctly
            currentChar = tmpLine.SubString(i, 1) '<-- Changed the MID call to .Net SubString
            If (currentChar = TABLE_VARIABLE_SYNTAX) Then
                If (check = False) Then
                    check = True
                    pos = i + 1 '<--- Added 1 since I changed the loop to be zero based
                Else
                    RaiseError("Unexpected variable symbol")
                    Return ""
                    'Removed the Exit Function since it will never be reached
                End If
            End If
            If (check = True) Then
                If (currentChar = " ") Then
                    varName = Replace(varName, TABLE_VARIABLE_SYNTAX, "")
                    varValue = Variables.GetVar(VarName)
                    tmpLine = RebuildString(tmpLine, varValue, pos, pos + Len(varName))
                    check = False
                    varName = ""
                    varValue = ""
                    done = False '<-- Added this
                    Exit For ' <-- Instead of a GOTO simply Exit the For loop
                End If
                If (i = posT - 1) Then ' <-- Added -1 since For loop is zero based
                    varName = Replace(varName, TABLE_VARIABLE_SYNTAX, "")
                    varValue = Variables.GetVar(varName)
                    tmpLine = RebuildString(tmpLine, varValue, pos, pos + Len(varName))
                    check = False
                    varName = ""
                End If
            End If
   
            If (check = True) Then
                varName = varName & currentChar
            End If
            done = True ' <--- Added this. This will never be set if we exit the For loop
        Next
    Loop Until done '<-- Added this

    Return tmpLine
End Function

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I put in comment for the changes I made but the main changes is that the code block is now inside a Do ... Loop Until loop instead of having a label and a GOTO statement.

I also changed your Mid call since that is an older function from VB6, a more ".Net way" of doing it is to call the String.SubString method.

I also changed the casing of all your local variables. It is a de facto standard in .Net to use camelCasing (first character in lower case) for local variables and PascalCase (first character in upper case) for methods, properties, and public fields.

I also removed a Exit Function line since you had a Return statement on the line before it. As soon as you hit a return the sub/function will exit. So the Exit Function was just redundant and you would never reach it.

I couldn't of course test this since I don't have all the necessary code but I hope I haven't introduced any errors.

Quote:

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Originally Posted by Joacim Andersson

End Function[/code]I put in comment for the changes I made but the main changes is that the code block is now inside a Do ... Loop Until loop instead of having a label and a GOTO statement.

I also changed your Mid call since that is an older function from VB6, a more ".Net way" of doing it is to call the String.SubString method.

I also changed the casing of all your local variables. It is a de facto standard in .Net to use camelCasing (first character in lower case) for local variables and PascalCase (first character in upper case) for methods, properties, and public fields.

I also removed a Exit Function line since you had a Return statement on the line before it. As soon as you hit a return the sub/function will exit. So the Exit Function was just redundant and you would never reach it.

I couldn't of course test this since I don't have all the necessary code but I hope I haven't introduced any errors.

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Okay this is indeed the better "other" solution, i appreciate this example, once this is seen i'd never go bad again. Thanks J.

-TB

The 'Goto is bad' is really a rule. Generally, the use of goto implies a programmer with limited experience, is unwilling to listen, is simply resting on their laurels, or all of the above.

Here's an example of using GOTO statements on a common algorithm:

Code:

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Public Sub DoSomething()
    Dim a() As Long = New Long() {6, 9, 2, 8, 1, 12, 5, 4, 0, 3, 2, 6, 4}
    Call DoSomething(a)
    Dim i As Integer = 0
12:
    Debug.WriteLine(a(i))
    i = i + 1
    If i < a.Length Then GoTo 12
  End Sub

  Public Sub DoSomething(ByVal a() As Long)
    Dim i As Integer = a.Length - 1
    Dim j As Integer = 0
a4:
    If a(j) > a(j + 1) Then GoTo 3
    j = j + 1
    If j = i Then GoTo 9
    GoTo a4
9:
    j = 0
    i = i - 1
    If i = 0 Then GoTo 5
7:
    GoTo a4
3:
    Dim t As Long
    t = a(j)
    a(j) = a(j + 1)
    a(j + 1) = t
    GoTo 7
5:
  End Sub

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As you can see, quite clear and concise. I would say that it's a pretty good example of 'bad' code. Feel free to copy it...maybe find the bug.

Quote:

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Originally Posted by SJWhiteley

The 'Goto is bad' is really a rule. Generally, the use of goto implies a programmer with limited experience, is unwilling to listen, is simply resting on their laurels, or all of the above.
[/CODE]

As you can see, quite clear and concise. I would say that it's a pretty good example of 'bad' code. Feel free to copy it...maybe find the bug.

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Prob all right but not of use to me atm because this has not very much todo with the project i am doing.

Replaced alote since last time, heres what i did.

- Parser replaced with a lexer (so much easier!)
- Functions accept parameters instead of compound variables
- Functions have theire own variable tables
- Global variables
- Do-loops (until/while/inf) statement are using the same comparision class as the if-then-else
- if-then-else supports (true/false or 1/0 or simple comparision methods)
- Line seperators multiple statements in one line
- Self made functions automaticly become a function within the engine and can be called from anywhere
- and alote of fine tuning...

Screen shot:
http://s18.postimage.org/qaruec1y1/editor.png