Problem with Function Returning Nothing

[DiverDan]

Here's my function:

   Private Function Adjust_Gauges4VoltageDrop(ByVal informationFrom As String, ByVal locationLine As Integer, ByVal conductorGauge As String, ByVal groundGauge As String, ByVal amperes As Double, ByVal numOfParallelConductors As Double, ByVal voltageDropPercent As Double) As String
       If INI_Info(121) = "without" Then Return "not required"

       Dim NECTable, conductorMaterial, tempGroup As String
       Dim voltage, numParallelConductors, Rwire As Double
       'get variable info
       If informationFrom = "Calc" Then
           NECTable = usageTable
           conductorMaterial = cbWireMaterial.Text
           tempGroup = InsulationTemperatureGroup
           voltage = Val(tbVolt.Text)
       ElseIf informationFrom = "Grid" Then
           NECTable = lvData.Items(locationLine).SubItems(Col(40)).Text
           conductorMaterial = lvData.Items(locationLine).SubItems(Col(24)).Text
           tempGroup = Val(lvData.Items(locationLine).SubItems(Col(41)).Text)
           voltage = Val(lvData.Items(locationLine).SubItems(Col(5)).Text)
                  End If
       'check voltage drop value
       If voltageDropPercent <= Val(INI_Info(120)) / 100 Then
           Return conductorGauge & "," & groundGauge & "," & voltageDropPercent
       Else 'increase conductor gauge value by 1
           conductorGauge = IncreaseGauge(conductorGauge)
           'increase ground gauge if necessary
           Dim maxAmps As Integer = Get_MaxAmps("Conductor", NECTable, conductorMaterial, tempGroup, voltage, conductorGauge) 'Max Conductor Ampacity
           Dim parallelConductorCount As Double = numOfParallelConductors
           If parallelConductorCount = 0 Then parallelConductorCount = 1
           GroundInfo = Split(Table250_122(maxAmps * parallelConductorCount, conductorMaterial), ",")
           groundGauge = convertGaugeFromAWG(INI_Info(62), GroundInfo(0))
           'Calculate Wire Resistance
           Rwire = Calc_Rwire(informationFrom, locationLine, conductorGauge)
           'get voltage drop percentage
           Dim voltageDrop As Double = Rwire * amperes 'Amps(actual)
           voltageDropPercent = voltageDrop / voltage
           'recurse
           Adjust_Gauges4VoltageDrop(informationFrom, locationLine, conductorGauge, groundGauge, amperes, numOfParallelConductors, voltageDropPercent)
       End If
   End Function

It calculates the gauges and voltage drop percentage perfectly but returns nothing as its value??? What have I done wrong this time?

 

Thanks

Dan

[wyrd]

Easiest way to find this problem is using the debugger. Set a break point at the first line of the function (click the sidebar at the side of your editor and a red dot will appear), then run the app in debug mode. When it reaches that function, it'll stop and allow you to look at the source and all values set thus far (little debug window at the bottom left of your screen). You can then use the step commands (should be on your menu bar) to step through each line of code. Check & verifty each value as you go through the function, and I'm sure you'll notice something out of place.

[DiverDan]

Thanks wyrd, but that's not the problem. I can use Return "dan" and still get nothing??? Using the debugger and a MessageBox.Show shows that the function is calculating perfectly and (if I can every figure why it returns nothing) will return a csv string with the correct values. This is the way I call the function:

 

       Dim adjustedGauges() As String = Split(Adjust_Gauges4VoltageDrop("Calc", 0, tbConductorGauge.Text, tbGroundGauge.Text, RemoveSeperator(items(Col(6))), numOfParallelConductors, VoltageDrop / Volts), ",")
       If Not adjustedGauges(0) = "not required" Then
           'adjustedGauges(0) = conductor gauge
           'adjustedGauges(1) = ground gauge
           'adjustedGauges(2) = voltage drop percent
           For i = 0 To UBound(adjustedGauges)
               MessageBox.Show("i = " & adjustedGauges(i))
           Next
       End If

i = nothing because nothing is received???

 

Thanks,

Dan

Edited March 15, 2004 by DiverDan

[wyrd]

Well, stepping through with the debugger should show exactly why it's returning nothing.

 

But anyway, by inspection, it looks like it's returning nothing because your recursive call isn't returning anything;

 

'recurse

Adjust_Gauges4VoltageDrop(informationFrom, locationLine, conductorGauge, groundGauge, amperes, numOfParallelConductors, voltageDropPercent)

[DiverDan]

In the If voltageDropPercent <= Val(INI_Info(120)) / 100 Then conditional if I put a MessageBox.Show(conductorGauge & "," & groundGauge & "," & voltageDropPercent) the correct answer will be displayed. Changing the Function to a Sub with a global variable will work, but it's not the correct way of accomplishing this task.

 

Thanks,

Dan

[wyrd]

Reread my reply. ;)

 

Try putting the keyword Return in front of this line;

Adjust_Gauges4VoltageDrop(informationFrom, locationLine, conductorGauge, groundGauge, amperes, numOfParallelConductors, voltageDropPercent)

 

Return Adjust_Gauges4VoltageDrop(informationFrom, locationLine, conductorGauge, groundGauge, amperes, numOfParallelConductors, voltageDropPercent)

 

:P

[DiverDan]

Hi again wyrd,

 

Return Adjust_Gauges4VoltageDrop(informationFrom, locationLine, conductorGauge, groundGauge, amperes, numOfParallelConductors, voltageDropPercent) will not work with a function as you can not return a function, only its computed results.

 

However,

Return informationFrom & "," & locationLine & "," & conductorGauge & "," & groundGauge & "," & amperes & "," & numOfParallelConductors & "," & voltageDropPercent

returned the correct values.

 

I really think the function is good...actually, very good. I think the way I called the function is not so very good and is producing the problem.

 

As stated earlier, if I change the Function into a Sub and set a global variable instead of Return, the correct values will be produced. But this is not the correct manner to solve this task, a function (similar to a class) is the correct method and I have definately missed something in calling the function.

 

Thanks,

Dan

[wyrd]

You can't return a function call in VB? Well anyway, just do this then (syntax may be off, I haven't done anything in VB for years);

 

Dim str As String = Adjust_Gauges4VoltageDrop(informationFrom, locationLine, conductorGauge, groundGauge, amperes, numOfParallelConductors, voltageDropPercent)

Return str

 

From what I can tell, the problem is that the recursive function call is not returning its results. So basically your function recursively calls Adjust_Gauges4VoltageDrop(...) and then abruptly ends. Because of that (you'd get an error in C# since you didn't return anything) your function is giving you Nothing as the return value.

 

If that doesn't work (it should, darnit), then you could just pass a string ByRef and use that to store the results (this is in response to your "global" solution). This would of course cause you to pass in another paremeter as a string, something like ByRef returnVal As String.

[dragon4spy]

There are many problems with your Function. I'm checking for you :D

[dragon4spy]

        'check voltage drop value
       If voltageDropPercent <= Val(INI_Info(120)) / 100 Then
           Return conductorGauge & "," & groundGauge & "," & voltageDropPercent   '<<<< Put break point here

 

Put a break point on this return line, and see when your function is exectuted, will it stop at the break point or not?

 

If nothing happen then it must be because voltageDropPercent > Val(INI_Info(120)) / 100 .

:rolleyes:

 

I suggest you to learn more about Debugger. I tell you I used to face this before when I started vb. :D

Edited March 15, 2004 by dragon4spy

[DiverDan]

I'm giving up...

The recursive function works just fine. Shy of an atmospheric nuclear explosion, voltageDropPercent > Val(INI_Info(120)) / 100 is absolutely impossible with the formulae and computations that are taking place. Larger diameter conductors with the same amperes will always have less resistance (Rwire) and therefore the resulting voltage drop will also always be less with no exceptions (it's an OHM's Law thing - which isn't really a law by defination but actually a relationship). If I use a string variable, as suggested by wyrd, then the correct values are returned, so that is what I have done as I have no more time to spend on this function today.

 

Thanks wyrd,

Dan