CODEWITHSUNDEEP
vb.net
user3511558
user3511558

Reputation: 5

Displaying the sum of a range of numbers?

I have to create a program that calculates the sum of a range of numbers entered by the user and displays in a label an expression with the numbers in range. So if I entered "10" as a starting number and "20" as an ending number, there would be a label that displays "10+11+12+13+14+15+16+17+18+19+20".

This is what I have so far. I'm not sure how to get the range of numbers and display it in a label. I'm also really new to Visual Basic (I'm taking it as a course in high school) so please dumb down your answer as much as possible :) Any help is appreciated! Thanks.

    Dim intStartingNumber As Integer = Val(Me.txtStartNumber.Text)
    Dim intEndingNumber As Integer = Val(Me.txtEndNumber.Text)
    Dim intSum As Integer = 0

    Me.lblNumbers.Text = intStartingNumber & "+" & intEndingNumber

    For intStartingNumber = Val(Me.txtStartNumber.Text) To intEndingNumber Step 1
        intSum = intSum + intStartingNumber
    Next
    Me.lblNumbersSum.Text = intSum

Upvotes: 0

Views: 8499

Answers (3)

mjsqu
mjsqu

Reputation: 5452

This should work, albeit I haven't been able to test:

Dim intStartingNumber As Integer = Val(Me.txtStartNumber.Text)
Dim intEndingNumber As Integer = Val(Me.txtEndNumber.Text)
Dim intSum As Integer = 0
Dim intIndex As Integer
Dim strExpr As String

strExpr = Me.txtStartNumber.Text

'Setting up a new variable called intIndex so that intStartingNumber can stay static
For intIndex = Val(Me.txtStartNumber.Text) To intEndingNumber Step 1
    intSum = intSum + intIndex
    if intIndex > intStartingNumber Then
      strExpr = strExpr & "+" & intIndex
    End If
Next
Me.lblNumbersSum.Text = intSum
Me.lblNumbers.Text = strExpr

The idea is that you create a new variable called strExpr to hold the expression and then concatenate using & within the For loop. That way, as you add on the values arithmetically, you're also adding to the string that shows the calculation being done. I'm hoping that's what you were after.

If you get any errors, please comment below and I'll amend the script and explain.

Upvotes: 0

Andrew Morton
Andrew Morton

Reputation: 25013

As you are doing this to learn the basics of Basic (hah hah, never heard that one before), I will keep it simple:

' convert the input text into numbers
Dim startNumber As Integer = Integer.Parse(txtStartNumber.Text)
Dim endNumber As Integer = Integer.Parse(txtEndNumber.Text)

'TODO: optional - check that endNumber > startNumber

' we are going to put the sum and the text of the summation into
' variables; we might as well start them off with the first values
Dim sum As Integer = startNumber
Dim sumText As String = startNumber.ToString()

' now we just need to use a loop that goes from the second value to the end
For i As Integer = startNumber + 1 To endNumber
    ' we need to use the value i twice, once as a number...
    sum = sum + i
    ' ... and once as a String
    sumText = sumText & "+" & i.ToString()
Next

' show the results to the user
lblNumbersSum.Text = sum.ToString()
lblNumbers.Text = sumText

The default Step value for a For..Next loop is 1, so we don't need to specify that.

Instead of writing sum = sum + i, we could write sum += i, and similarly for sumText = sumText & "+" & i.ToString() we could write sumText &= "+" & i.ToString(). They are just ways of saving a bit of typing.

As Jens mentioned, it is usually better to use something called a StringBuilder to build a string in a loop, but I expect you will learn about that later. If you want to learn about it now, you could look at the Remarks section of the StringBuilder documentation.

Upvotes: 0

Joel Coehoorn
Joel Coehoorn

Reputation: 415725

If you just want the total:

Dim StartNumber As Integer = Integer.Parse(txtStartNumber.Text)
Dim EndNumber As Integer = Integer.Parse(txtEndNumber.Text)

lblNumbersSum.Text = Enumerable.Range(StartNumber, EndNumber - StartNumber ).Sum()

If you really want the full text expressions:

Dim StartNumber As Integer = Integer.Parse(txtStartNumber.Text)
Dim EndNumber As Integer = Integer.Parse(txtEndNumber.Text)
Dim delimiter As String = ""
Dim expression As New StringBuilder()

For Each number As String IN Enumerable.Range(StartNumber, EndNumber - StartNumber )
     expression.Append(delimiter).Append(number)
     delimiter = "+"
Next number

lblNumbersSum.Text = expression.ToString()

Upvotes: 2

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