Parallel Array Carver with Visual Basic

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I'm writing a program the allows Professor Carver to display a grade based on the number of possible points he enters in the inputbox (strMax). Then the user enters the points he earned in the textbox (dblPoints)

Then I solve the percentage. dblResults = dblPoints/CDbl(strMax)

The first step is to store the minimum percentage points in one dimensional array. I did that.

The second step is to store the grades in one dimensional array. I did that.

The arrays should be parallel arrays. <------ Having trouble with it

It then should display the corresponding grade from the strGrades array <---- Not done.

I'm having trouble to display arrays in that are parallel. The problem is the for loop

I tried this

VB

For intGrade As Integer = 0 To 4
         If dblResults <= dblPer(intGrade) Then
             lblGrade.Text = strGrade(intGrade + 1)
         ElseIf dblResults >= dblPer(0) Then
             lblGrade.Text = strGrade(0)
         Else
             lblGrade.Text = strGrade(4)
         End If
     Next intGrade

I'm getting the error that says "Index was outside the bounds of the array." There's something wrong with the strGrade(intGrade+1), but no idea how to fix this.

I also tried this way

VB

For intGrade As Integer = 0 To 4
    If dblResults >= dblPer(intGrade) Then
        lblGrade.Text = strGrade(intGrade + 1)
    End If
Next intGrade

Still getting the same error?

Any help with the if statements? I don't understand what's wrong.

Thanks.

Here is the code in case you don't understand

Private Sub btnDisplay_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnDisplay.Click
        ' display the grade the student gets
        Dim dblPoints As Double
        Dim dblResults As Double
        Dim strGrade() As String =
            {"A", "B", "C", "D", "F"}
        Dim dblPer() As Double =
            {0.9, 0.8, 0.7, 0.6, 0.5}

        Double.TryParse(txtPoints.Text, dblPoints)
        ' displays the percentage the student recieves
        dblResults = dblPoints / CDbl(strMax)
        ' determines the grade

        For intGrade As Integer = 0 To 4
            If dblResults >= dblPer(intGrade) Then
                lblGrade.Text = strGrade(intGrade + 1)
            End If
        Next intGrade


    End Sub
   Private Sub frmMain_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        ' get the total number of possible points
        strMax =
            InputBox("Enter the total possible points.", "Professor Carver")

    End Sub

Posted 6-Nov-11 5:57am

byron luo

Updated 6-Nov-11 7:23am

v4

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Comments

LanFanNinja 9-Nov-11 18:49pm

I have added a solution for your problem below even though it is a little late I wanted to post it anyway so you can know what the problems were just in case you did not figure it out.

2 solutions

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LanFanNinja · Answer 1 · 2011-11-09T12:42:00

In addition to what SAKryukov posted in solution 2 which does indeed need to be done! This is my modifications to your code to fix your problems.

change

VB

Dim dblPer() As Double =
    {0.9, 0.8, 0.7, 0.6, 0.5}

to this

VB

Dim dblPer() As Double =
    {0.9, 0.8, 0.7, 0.6, 0.0}

then change this

VB

For intGrade As Integer = 0 To 4
    If dblResults >= dblPer(intGrade) Then
        lblGrade.Text = strGrade(intGrade + 1)
    End If
Next intGrade

to this

VB

For intGrade As Integer = 0 To dblPer.Length
    If dblResults >= dblPer(intGrade) Then
        lblGrade.Text = strGrade(intGrade)
        Exit For
    End If
Next intGrade

A little late I know but I hope it helps.

Sergey Alexandrovich Kryukov · Answer 2 · 2011-11-06T07:19:00

This is a simple bug; instead of lblGrade.Text = strGrade(intGrade + 1) use lblGrade.Text = strGrade(intGrade). The indexes should run from 0 to strGrade.Length - 1.

An important note: using immediate constant of 4 is not reliable. Actually, this is another bug which will not be manifested… just yet, but can easily haunt you later. Always use Length for arrays, Count for collections, etc.

A bonus advice: get rid of you Hungarian notation. For .NET, it makes no sense at all. Just make all names semantic, use proper case; generally, find (good) Microsoft naming conventions and use them. In practice, this is not insignificant detail, no, this is important — in practice.

—SA

Parallel Array Carver with Visual Basic

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Solution 2

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