debugging help

[stuart1512]

the next stage in the tutorial is debugging, ive got the code theyve said and like they said, i cant find whats wrong and am saying to myself that it should work LOL

heres the code

Dim I As Integer
Dim LetterCount As Integer
Dim strText As String
Dim Letter As Char

strText = "Debugging"

For I = 1 To strText.Length - 1
Letter = strText.Substring(0)

If Letter = "g" Then
LetterCount = LetterCount + 1
End If
Next
TextBox1.Text = "g Appears" & " " & LetterCount & " " & "Times"
End Sub

thanks in advance


can u spot whats going wrong please???

[BackWoodsCoder]

well, break the program down logically.

What is it trying to do? Count the number of times "g" appears in a word
How does it do that? the loop
What's not working? I'm guessing it's outputting zero for you.

So, if it's not "working" and the thing that's supposed to make it "work" is your loop, where do you think the first place you should look at to solve the issue? I'll give you a nudge, it is a problem to do with an index.

[stuart1512]

i have no idea what you just said. ive only been doing this for a few weeks and am still not confident enough. im still on tutorial materials could you please tell me which line it is on

[BackWoodsCoder]

Well, I'm not going to give you the answer. What purpose would that serve? You're there to learn and if you really do want to learn about programming, learning the why is infinitely more important then knowing the how.

For I = 1 To strText.Length - 1
Letter = strText.Substring(0)
 
If Letter = "g" Then
LetterCount = LetterCount + 1
End If
Next

This is basically the "guts" of your program. What this is doing is reading the length (how many characters) of your string variable strText and using that to count how many times to go through the loop.

Looking at it now there is a problem with your loop to begin with. In VB (and pretty much every other language) loops and lists and arrays are all ZERO based. Which means instead of starting at 1 to count the objects they contain, they start at 0. See one of your problems yet?

Right underneath your loop is a method of the string class called substring. When ever you see something in code you don't understand, press F1 in visual studio to bring up help and search on it! If you need a better explanation, google or go to MSDN's site and read more documentation. Read, read, read, read. There will be points in time where you hit problems and must utilize your resources to solve them, now's a good time to start learning where and how to look for answers to your problem

Anyways, what substring does is return a smaller portion of a large string. This is useful for breaking up large strings, grabbing specific portions of strings, etc. What it's doing here in your code is looking at individual characters in your string variable strText. See the (0) in the substring line? That's saying "return the character at position ZERO". However, it never moves from zero so it will always return "d". So in order for it to move from (0) you need to tell it to, and you do that with a variable that increases by 1 each time the loop iterates.

Do you see a variable in your loop that meets those conditions? If so, where would you put it?

[stuart1512]

i still dont get the answer, its just a load of garble to me, all i want to know is what is wrong, then i will understand

[BackWoodsCoder]

how will you understand if you don't even understand where the problem is coming from in the first place? I've pretty much laid out the problems with your code, can you at least take a guess at the lines in which the problems are occurring?

[stuart1512]

ive been learning for 2 weeks ONLY. this is my first ever programming and i am not used to looking through and thinking about he answers for myself much, please just tell me what i have to do

[gonzalioz]

Hi there,
Backwoodscoder pretty much said it all but maybe you'll understand it in a different context:

The problem is in your loop:

For I = 1 To strText.Length - 1
Letter = strText.Substring(0)

If Letter = "g" Then
LetterCount = LetterCount + 1
End If
Next

To your program the letters in strText are numbered like this:
D = 0
E = 1
B = 2
B = 3
U = 4
G = 5
G= 6
I = 7
N = 8
G = 9

Your loop says this: start from number 1 to number 9
So your not checking the letter D at place 0!

That is one problem, the 2nd is at this line:

Letter = strText.Substring(0)

Look at the 0 you placed beteween the brackets of Substring(). That of course should be I.

If you changed those things this is what the loop would do:

I = 0
letter = D
letter is not g

next

I = 1
letter = E
letter is not g

next

I = 2

etc... You get the idea


So what your code should be like:

For I = 0 To strText.Length - 1
Letter = strText.Substring(I)

If Letter = "g" Then
LetterCount = LetterCount + 1
End If
Next

Hopefully that helped!

[BackWoodsCoder]

Hopefully that helped!

I'd hope so, you just fed him the answer lol!

[stuart1512]

thanks gonzalioz. i was just about to give up on the whole thing

[gonzalioz]

No problem, I know you can sometimes just look at a code for hours and can't spot the problem. But I would suggest following this tutorial:

http://www.homeandlearn.co.uk/NET/vbNet.html

That's how I started 7 weeks ago. It's a great tutorial. Very easy to read and very good explanation.

This is the chapter about loops, if you didn't understand all of it yet:
http://www.homeandlearn.co.uk/NET/nets3p1.html

[stuart1512]

thats the tutorial im using, its great but i just dont understand it at times