Functions and SubRoutines

I am taking a programming class and am having some trouble grasping some of this stuff. I am new to programming and was hoping maybe someone could maybe explain this to me in "plain english"? Any help would be most appreciated.........The following is the assignment I am having some trouble with.


Fun with Functions and Subroutines

· Create a subroutine (not a function) called SquareIt that will take a decimal number and square it. Use module-level vars for the decimal number and the result. Do not use parameters. In a button click event, call SquareIt. After it returns, display a message box that displays something like, "The square of 5 is 25".

· Create a subroutine similar to as above, except use 2 parameters instead of module-level variables. The first parameter will be the decimal number to square. The second parameter will be a ByRef parameter that can be used to hold the squared decimal. Once again, display a message box as above.

· Do the same as above, but make it a function called Square. Square takes one parameter (the decimal number to square), and returns the squared decimal number in its return value. Once again, display a message box as above.




· Create a subroutine called ValidateRange that checks to see if an integer is within a specified range of numbers. Use parameters. The first parameter will be the integer to check. The second parameter will be the minimum number that is acceptable. The third parameter will be the maximum number that is acceptable. The fourth parameter is a boolean called bValid that holds whether the number is in range. In a button click event, call ValidateRange. After it returns, display a message box that displays something like, "The number 63 is not in range". Or, the number 7 is in range.

· Create a function called ValidRange that does the same thing except that it take just one parameter (the number to check) and returns the boolean in its return value. Once again, display a message box as above.




· Create a function called MonthName that accepts one integer parameter from 1 to 12 representing a month in the year. For example, 1 corresponds to January. The function should return a String representing the name of the month.

· Enhance the MonthName function so that it validates that the incoming parameter is in the range of 1 to 12. If it's not, return an empty string:

Return ""

What is it that you don't understand? If you ask more specific questions you'll probably get more answers.

The main difference between a Sub (Subroutine) And A Function is that a function returns a value. Typically you assign something to the function result (i.e dim result=GetUser) and Subs just get called (i.e SetUser). If a parameter is passed into a sub ByRef then the Sub can motify the variable as it passes through otherwise it gets passed ByVal and any changes don't occur outside of the sub. So by passing a parameter into a Sub ByRef you can use a Sub a lot like a Function.

I guess I am looking for an example...I mean could some one show me what this means with one of my problems?

Well I'm not going to do your homework for you but to give you a nudge here would be the method signatures for the required methods. A method signature is just the declaration part of the method.

VB Code:

'#1
Public Sub SquareIt()
 
'#2
Public Sub SquareIt(ByVal toSquare As Single,ByRef result As Single)
 
'#3
Public Function SquareIt(ByVal toSquare As Single) As Single
 
'#4
Public Sub ValidateRange(ByVal number As Integer, ByVal min As Integer, ByVal max As Integer, ByRef bValid As Boolean)
 
'#5
Public Function ValidateRange(ByVal number As Integer) As Boolean

Thank You.....thats a start.

:)

Nice nudge Edneeis :D.

I have been messing with this for hours and this still makes absolutley no sense to me......I really want to understand this,although I have no ambitions of being a software engineer....could anyone please try to explain this in english without all the 'programming slang"
Thank You so much

You gotta do the one thing where the deal messes with the thing and sends it back. Then do it again but with the things switched around and then where it returns the thing.

:)


Just kidding. So whats the problem exactly? Try asking specific questions. What don't you understand? What do you have so far? Post some code.

ok, Well first of all I posted the assignment and I dont understand what it is my Instructor is asking for nor do any of the other students in my class, but he isnt giving any clarification so i am trying to understand what it is on my own, to no avail. I will work a bit more on it and get back to you......than you so mcuh for answering me though, I truly appreciate it......

It looks like he is teaching you the difference between Functions, Subs, and ByRef, ByVal. See most of these are doing the samething, just in different ways. Like all the SquareIt things do the exact same thing just in different ways.

Fun with Functions and Subroutines

For the problems below, you'll need to create a single form.

· Add a textbox to the form called txtNbr, and a button with the caption SquareItMod. Create a subroutine (not a function) called SquareItMod that will take a decimal number from txtNbr and square it. Use module-level vars for the decimal number and the result. Do not use parameters. In the button click event, call SquareIt. After it returns, display a message box that displays something like, "The square of 5 is 25".

· Add a button with the caption SquareItParm to the form. Create a subroutine named SquareItParm, similar to the above, except use 2 parameters instead of module-level variables. The first parameter will be the decimal number to square. The second parameter will be a ByRef parameter that can be used to hold the squared decimal. Once again, display a message box as above, when the button is clicked.

· Add a button with the caption Square, to the form. Do the same as above, but make it a function called Square. Square takes one parameter (the decimal number to square), and returns the squared decimal number in its return value. Once again, display a message box as above, when the button is clicked.




· Add a button with the caption ValidateRange to the form. Add 2 more textboxes to the form, called txtMin and txtMax. Create a subroutine called ValidateRange that checks to see if an integer is within a specified range of numbers. Use parameters. The first parameter will be the integer to check, taken from the txtNbr textbox. The second parameter will be the minimum number that is acceptable, taken from txtMin. The third parameter will be the maximum number that is acceptable, taken from txtMax. The fourth parameter is a boolean called bValid that holds whether the number is in range. In the button click event, call ValidateRange. After it returns, display a message box that displays something like, "The number 63 is not in range". Or, "The number 7 is in range".

· Add a button with the caption ValidRange to the form. Create a function called ValidRange that does the same thing as above, except that it takes three parameters (the number to check, the minimum number, the maximum number) and returns the boolean in its return value. Once again, display a message box as above when the button is clicked.



NOW HE HAS CHANGED THE WHOLE THING......

THIS IS HIS NEW UPDATE:


· Add a button with the caption MonthName to the form. Create a function called MonthName that accepts one integer parameter (taken from txtNbr). The function should return a String representing the name of the month. For example, if the user enters 1, display "January" in a message box. If the user enters 3, display "March". Call the function when the user clicks on the button.

· Enhance the MonthName function so that it validates that the incoming parameter is in the range of 1 to 12. If it's not, return an empty string:

Return ""

Note that, for the above two problems, you only need to turn in ONE function called MonthName that incorporates the functionality of both.

THIS IS HIS NEW UPDATE

Nicky, it seems like this instructor is trying to teach you guys run first instead of walking :p j/k.

Seriously though, can you answer these questions?

1. Do you know what a module is?
2. Do you understand what global variables are?
3. Do you understand the difference between a function and a subroutine?
4. Do the know the difference between ByRef and ByVal?
5. Do you know what an if statement is?
6. Do you know what a select statement is?

What you have to do is not hard at all, you just need a better grasp of the programming concepts. BTW what text book are you using?

Module-I beleive is a Var that can be used in any procudre or something

global- can be used anywhere in the project

functions and subroutines are what i am not getting at all

I can look up the definitons for you......I am not a programmer and I really dont understand this stuff, but i am really trying to.
I know how to use If statements......

I am using the text "Programming In Visual Basic.Net" by Julia Case Bradley.

The book was great the first 3 chapters and then varibles came along and I got lost and now we are doing this stuff and he doesnt explain it well......just does a few examples and says....there u go.....now go program, I am not looking for anyone to do my assignments for me.........just maybe explain it like a recipe or something....lol. I dont know

SCREAMING!!

lol
ty for replying.......hope to hear from you again

Hello again,

I have an example, my instructors example of how we are to build our code.....similar to how he did his. Now this is what I am wondering if one of you guys "please" could do for me. In remarks if you could, under each statemnet of code, just explain what is going on that way I might be abole to decipher what is going on...through the 3 books I have bought and my text and notes I am gathering throughout the web, maybe I can grasp this stuff.....I know its asking alot, but i would be so grateful for any hlep.
Thank you all!!

N

Zip up the project and post the whole thing so we can see if you are doing things right. BTW is this your first time programming?

I'll comment the code for you an report back.

DevGrp out. :D

Ok, this code should be self explanitory. All thats going on is some basic validation. Checking for negative numbers, numerics, and empty textboxes.

VB Code:

Private Sub btnSave_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSave.Click
 
    Try
        If txtNbr1.Text = "" Then
            MessageBox.Show("This field must not be blank")
            txtNbr1.Focus()
        ElseIf Not IsNumeric(txtNbr1.Text) Then
            MessageBox.Show("This field must be numeric")
            txtNbr1.Focus()
        ElseIf ToDecimal(txtNbr1.Text) <= 0 Then
            MessageBox.Show("This field must be greater than zero")
            txtNbr1.Focus()
        ElseIf txtNbr2.Text = "" Then
            MessageBox.Show("This field must not be blank")
            txtNbr2.Focus()
        ElseIf Not IsNumeric(txtNbr2.Text) The
            MessageBox.Show("This field must be numeric")
            txtNbr2.Focus()
        ElseIf ToDecimal(txtNbr2.Text) <= 0 Then
            MessageBox.Show("This field must be greater than zero")
            txtNbr2.Focus()
        ElseIf txtNbr3.Text = "" Then
            MessageBox.Show("This field must not be blank")
            txtNbr3.Focus()
        ElseIf Not IsNumeric(txtNbr3.Text) Then
            MessageBox.Show("This field must be numeric")
            txtNbr3.Focus()
        ElseIf ToDecimal(txtNbr3.Text) <= 0 Then
            MessageBox.Show("This field must be greater than zero")
            txtNbr3.Focus()
        Else
            MessageBox.Show("Data has been saved")
    End If
 
    Catch Ex As Exception
        MessageBox.Show(Ex.ToString, "Unexpected Error")
        Application.Exit()
    End Try
 
End Sub

Ok I see that you have made a SubRoutine to validate the texboxes on the form. Thats good. Now as you can see this subroutine does not return a value, thats why its called a subroutine. If it was to return a value, it would be called a function. To change this to function you would just change the word Sub to Function put the type of return value at the end.

eg.Function ValidateField() As Boolean

In that case Boolean would be the return value, which would be a true or false.

VB Code:

Private Sub ValidateField()
 
    Try
        If m_txtNbr.Text = "" Then
            MessageBox.Show("This field must not be blank")
            m_txtNbr.Focus()
            m_bInvalidField = True
        ElseIf Not IsNumeric(m_txtNbr.Text) Then
            MessageBox.Show("This field must be numeric")
            m_txtNbr.Focus()
            m_bInvalidField = True
        ElseIf ToDecimal(m_txtNbr.Text) <= 0 Then
            MessageBox.Show("This field must be greater than zero")
            m_txtNbr.Focus()
            m_bInvalidField = True
        Else
            m_bInvalidField = False
        End If
 
    Catch Ex As Exception
        MessageBox.Show(Ex.ToString, "Unexpected Error")
        Application.Exit()
    End Try
End Sub

I looked at the file. You seem to know what you are doing.

Ok you said you are not getting Functions and Subroutines.

Ok here goes. To understand them better, do not think of them as functions or subroutines. Just think of them as Methods. Just remember that Methods that return a value should be declared with the function keyword and Methods that does not return a value should be declared with the sub keyword.

Here is an example.

VB Code:

'[b]This is a method that takes two integers parameters and returns an integer value (Function)[/b]
 
Function AddNums(ByVal num1 as Integer, num2 as Integer) as Integer
 
      return num1 + num2
 
End Function
 
'[b]This method does take any parameters and do not return a value (Sub)[/b]
Sub AddNums()
      
      Dim num1 , num2 as Integer
      
      num1 = 12
      num2 = 36 
      
      MessageBox.Show(num1 + num2)
 
End Sub

Dev,
No I dont know what I am doing as this isnt MY code, its my Instructors... he sent it out as an example. I will use your notes though ......thank you so much for taking the time to look.

Hello Once again........I am still not getting this stuff.......how do I write the code? I mean.......it says I need to add a textbox named txtNBR which I have done and then I am too create a Subroutine...which I did, but i dont understand where am I supposed to put the code? In the btn click event or in the sub? how do I get it to square whatever the used puts in the box?
I have been playing with this all week.....and nothing seems to make sense......can I hire someone to tutor me?
I am desperate here

ty

Quote:

---

Hello Once again........I am still not getting this stuff.......how do I write the code? I mean.......it says I need to add a textbox named txtNBR which I have done and then I am too create a Subroutine...which I did, but i dont understand where am I supposed to put the code? In the btn click event or in the sub? how do I get it to square whatever the used puts in the box?

---

Ok Check this out, you can either create the subroutine inside the form where its going to be used or create a module, then create the all your functions and subroutines in it.

To square whatever in put in the text box, you are going to have to parse the data. To parse the data from the TextBox, here is the SquareIt Subroutine.

VB Code:

Sub SquareIt(ByVal txtBox As TextBox)
        Dim num As Decimal
        Dim square As Decimal
 
        num = Decimal.Parse(txtBox.Text)
 
        square = num * num
 
        MessageBox.Show("The Square of " & num & " is " & square)
End Sub

I am using VB.Net Visual Studio


Public Class frmSquareIt
Inherits System.Windows.Forms.Form
Public Sub SquareItMod()

Dim m_decNumber As Decimal
Dim m_decResult As Decimal=5

m_decNumber = CDec(txtNbr.Text)
m_decResult = CDec(txtNbr.Text)

MsgBox(m_decNumber ^ m_decResult)

End Sub

#Region " Windows Form Designer generated code "




Private Sub btnSquare_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSquare.Click
Call SquareItMod()

End Sub
End Class

Ok
I got the first one to work, now onto the 2nd one.......

Ok, now try and do the others. And always remember the more sweat in training the less you bleed in combat, so do some experiementing, read ahead and practice practice practice :D.

What is a Parameter? ........Its says I need to add parameters instead of varibles......The first par. will be the decimal number to square and the second will be a BYRef that can be used to hold the squared decimal.

Parameters are values that will be passed to the function when it is called.

eg:

VB Code:

Function MonthName(ByVal mnt As Integer) As String 'mnt is the parameter being passed

When you pass parameters to functions. You can either pass them by value (ByVal) or by reference (ByRef). ByVal is the default way for passing parameters. When parameters are passed by value, you are making a copy of the variable and passing it to the function or sub. Parameters passed by reference is a pointer to the memory address where that varible is stored. So it you passed a param by ref, you would be modifying the original variable instead of a copy, which is case if you passed a param by value. I hope that made sense.:p

CAN YOU SHOW ME HOW TO DO THIS? I DONT GET IT......I need to hire a programmer.....do you know of any as this is not making sense to me.......I will FAIL and LOSE my WHOLE educatioon if I DONT pass this




Add a button with the caption SquareItParm to the form. Create a subroutine named SquareItParm, similar to the above, except use 2 parameters instead of module-level variables. The first parameter will be the decimal number to square. The second parameter will be a ByRef parameter that can be used to hold the squared decimal. Once again, display a message box as above, when the button is clicked.

· Add a button with the caption Square, to the form. Do the same as above, but make it a function called Square. Square takes one parameter (the decimal number to square), and returns the squared decimal number in its return value. Once again, display a message box as above, when the button is clicked.
:mad:

Ok, you need to calm down , I dont think you're gonna lose your education if you fail one class :D. I dont think I would be helping you much if I wrote the function for you. :) . Look at the examples that Edneeis provided and see if you can figure it out. Anyway I'm going to sleep now. I'll keep posting if you need anymore help.

Thank You :):)

No prob. How did you do?