compiler out of compiler - declaring variables using array

03-04-2007, 06:54 PM

slowchem

Newcomer

Join Date: Sep 2006

Posts: 8

compiler out of compiler - declaring variables using array

im trying to make a simple application that its like a compiler out of compiler...
got richtextbox where i put syntaxes/codes...

but i got problem with the declaration...
the only way i know to declare variables from my richtextbox to
my code is to use an array.. and then store it as array again

the syntax for my compiler out of compiler declaration:
DECLARE <DATA TYPE> <variable name>
ex: DECLARE NUMBER num1

Code:

        Dim linesyntax() As String = line.Split(" ".ToCharArray)
        Dim numberVariable() As Integer
        Dim nv As Integer
        nv = 0

        Select Case linesyntax(0).ToUpper

            Case "DECLARE"
                Select Case linesyntax(1).ToUpper
                    Case "NUMBER"
                        numberVariable(nv) = linesyntax(2)
                        ListBox1.Items.Add(numberVariable(nv))

                    Case "ALPHABET" 'Char
                    Case "TRULSE" 'Boolean
                    Case "FLOATIMAL" 'decimal
                End Select

            Case "PRINT"
         
        End Select

i got this error Unhandled exception of type 'System.NullReferenceException'
any tip how to fix this?
or are there any other way how to do what im trying to do?

thanks

03-04-2007, 09:43 PM

jo0ls

Senior Contributor

Forum Leader
* Expert *

Join Date: Feb 2005

Location: London

Posts: 1,050

numberVariable isn't initialized, hence the error.

It's probably easier to use a List, rather than an array, as you won't know the size beforehand.

I think it cries out for a generic dictionary though:

Code:

Dim numbers As New Dictionary(Of String, Integer)
' DECLARE NUMBER X
numbers.Add("X", 0)   ' add a dictionary entry, key = "X", value = 0
' X = 100
numbers("X") = 100

In vb2003 you could use a hashtable.

"TRULSE"

03-05-2007, 11:00 AM

slowchem

Newcomer

Join Date: Sep 2006

Posts: 8

Quote:

Originally Posted by jo0ls

Code:

Dim numbers As New Dictionary(Of String, Integer)
' DECLARE NUMBER X
numbers.Add("X", 0)   ' add a dictionary entry, key = "X", value = 0
' X = 100
numbers("X") = 100

In vb2003 you could use a hashtable.

"TRULSE"

i got the idea of using dictionary and i tried your code
but the parameters (Of String, Integer) gives me an error..
and it's DictionaryEntry in VB.net
i tried searching google/books on how to use dictionary
but i cant get any info how to use it in vb.net...

can anyone give me a link? thanks

03-05-2007, 01:04 PM

wayneph

Web Junkie

Retired Moderator
* Expert *

Join Date: Apr 2004

Location: D/FW, Texas, USA

Posts: 8,393

Quote:

Originally Posted by jo0ls

In vb2003 you could use a hashtable.

Or if you're using vb2005 then you need to make sure the right namespace is imported. Then the Dictionary will be available.

System.Collections.Generic

__________________
-- wayne, MSSM Retired
> SELECT * FROM users WHERE clue > 0
0 rows returned

03-09-2007, 01:34 AM

slowchem

Newcomer

Join Date: Sep 2006

Posts: 8

Quote:

Originally Posted by wayneph

Or if you're using vb2005 then you need to make sure the right namespace is imported. Then the Dictionary will be available.

System.Collections.Generic

thanks for the link, ill try to learn that later...

anyway, is it possible to add an item into a specific line in a listbox?
i'd tried search function but i cant find related about this question...

because i want to add a command "GOTOXY" like in C++
gotoxy(x,y)
where x = maybe spaces " " but using spaces it will erase all underneath it
and y = listbox line

thanks

03-09-2007, 08:19 AM

slowchem

Newcomer

Join Date: Sep 2006

Posts: 8

i get it now,
listbox1.items.insert(gotoy, additem)
and also the gotox part