# 1

Using Procedures and Functions

Using Procedures and Functions

What is a procedure?

What is a sub procedure (subroutine)?

Built-in functions in your code

What is a function?

CS 105 Spring 2010

# 2CS 105 Spring 2010

Procedures

A procedure is a block of programming code.

• There are two kinds of procedures:1.Subroutines (sub procedures)2.Functions

If we have to repeat code, we isolate it in a subroutine or function in order to avoid programming or typographical errors and make our code easier to debug or change—you only have to change it in one place!

# 3CS 105 Spring 2010

Calling Sub Procedures Calling Sub Procedures

We can invoke or call each sub procedure when we wish to perform those operations. Just write the name of the sub procedure.

CommissionFormat

(must give name of work sheet or place the code is stored if the sub procedure is not in “Modules")

CommissionFormat

# 4CS 105 Spring 2010

Private Sub versus Public Sub

Private Sub means the procedure can only be called from other procedures in its object (like a UserForm, or worksheet).

Sub means available to all worksheets, can be called from any procedure in any sheet.

Sheet1.CommissionCommission

# 5CS 105 Spring 2010

For Excel to use it, and for each spreadsheet to use it, where should the public function be?

A public function in a module can be accessed from all worksheets.

# 6CS 105 Spring 2010

Functions and Subroutines

The main difference:

• Functions do things and return a value.

strNew=Reverse(Cells(1,1).Value)

• Sub(routine)s do things, but do not return values.

MsgBox "Welcome",vbExclamation, "Hi”

Format 2

# 7CS 105 Spring 2010

Excel has many built-in functionsthat are the same as VBA functions,

and vice-versa

# 8CS 105 Spring 2010

VBA Functions

Predefined:

A. vntAnswer = MsgBox("Quit?", vbYesNo, "Leaving?")

B. If IsNumeric(strName) = True Then

A Function is just like a subroutine, except that it • returns a value to a variable or cell (A.)or• is evaluated on the fly as above (B.)

# 9

Quick Quiz

What do we mean by IsNumeric returns True or False “on the fly”?

The Value T or F is used immediately and discarded.

For example, the content of a page that is sent to you from a Web site can be varied "on the fly" based on what pages you looked at previously—the page is dynamic and will change

• BCS 105 Spring 2010

# 10CS 105 Spring 2010

Functions

The value returned by a function can be True, False, a value, vbYes, etc.

• You invoke (CALL) a Function by mentioning its name (typically as part of a larger expression), together with its argument(s).

• Sometimes a function doesn’t have arguments—you cannot tell for sure by looking at the statement calling the function, but you can tell by looking at how the function is written.

Cells(1,1).Value =Now()

# 11CS 105 Spring 2010

We can create our own functions

• Reverse(strWord) is at the heart of the function

• The function Reverse wants an argument, either a cell address or a word, and then it will reverse the letters in the word

• With functions such as Average, Count, etc. we need to feed them an argument

# 12CS 105 Spring 2010

Defining a Function

Function Useful(strName as String, intNumber as Integer) As String

Do something here

Useful = "a string of some sort"

End Function

Parameters

Body

Name Type of Return Value

# 13CS 105 Spring 2010

Parameter vs. Argument

You *declare* a function/sub procedure using something like this:

Function Reverse(strWord as String) As String

- strWord is called a *parameter* of the function Reverse

You *call* a function/sub procedure using something like the following:

Cells(1,1).Value = Reverse(strEntry)

strEntry (or the value in a cell) is called an *argument* that you *pass* to the function Reverse. Note: what you pass to the parameter can have a different name than the parameter has.

# 14CS 105 Spring 2010

So…• To connect the two, a function/sub procedure

defines a parameter, and the calling code passes a value/variable as an argument to that parameter.

• You can think of the parameter as a parking place and the argument as an automobile.

• Just as different automobiles can park in the parking place at different times, the calling code can pass a different argument to the same parameter each time it calls the procedure.

# 15CS 105 Spring 2010

Functions: Returning a Value

Function FixFormat(strName as String, intNumber as Integer) As String

FixFormat = strName & " " & intNumber

End Function

# 16

Private Sub cmdNew_Click()Dim strWord As StringDim strNoun As StringDim intQuantity As Integer

strNoun = Cells(1, 2).ValueintQuantity = Cells(2, 4).Value

strWord = FixFormat(strNoun, intQuantity)MsgBox "The result is " & strWord

End Sub-------------------------------------------------------------------------------------------

Function FixFormat(strName as String, intNumber as Integer) As String

FixFormat = strName & " " & intNumber

End Function

Joe

78

strNoun intQuantity

Joe 78

# 17CS 105 Spring 2010

Calling Functions

Dim strAnswer as String

strAnswer = DoCalculation(17)

…

What is the name of the function? DoCalculation

What type of value does it return?

How many arguments does it have?

What are the type(s) of argument(s)?

Better be a String

One

Probably an Integer

# 18CS 105 Spring 2010

To Summarize:

• What is a procedure?

• What is a sub procedure (subroutine)?

• Built-in functions in your code

• What is a function?