Advanced functions visual Basic .net

AUTHOR: MOHAMMED ABDEL KHALEQ DWIKAT EMAIL: dwikatmo@gmail.com
TOPIC: VISUAL BASIC II / FUNCTIONS/SUBS DATE: 1/31/2020 PAGE: 1 OF 7
VVIISSUUAALL BBAASSIICC ((IIII))
AANN NNAAJJAAHH NNAATTIIOONNAALL UUNNIIVVEERRSSIITTYY
MMAANNAAGGEEMMEENNTT IINNFFOORRMMAATTIIOONN SSYYSSTTEEMMSS
PPRREEPPAARREEDD BBYY::
MMOOHHAAMMMMEEDD AABBDDEELL KKHHAALLEEQQ DDWWIIKKAATT
dwikatmo@najah.edu
:facebook.com/dwikatmo
: dwikatmo@gmail.com
3311//0011//22002200
UUSSIINNGG AADDVVAANNCCEEDD FFUUNNCCTTIIOONNSS//SSUUBBSS
Iteration vs. Recursion
Passing Parameters by reference
Passing Arrays as parameters
Optional Parameters
Overloading

IITTEERRAATTIIOONN VVSS.. RREECCUURRSSIIOONN
Iteration is done by using loops, while recursion means the
function call itself.
Principle in recursion, if we can find or calculate process
N times, we can decompose it in N + (N-1) + (N-2) till the
stopping rule.
For example, instead of using the loop to sum from 1 to 5,
we can use recursion to sum it as follows
Sum (5) is
5 + Sum (4)
5 + 4 + Sum (3)
5 + 4 + 3 + Sum (2)
5 + 4 + 3 + 2 + Sum (1)
5 + 4 + 3 + 2 + 1
It works using a stack exactly like the following steps
Stack Rule: Last in First Out (LIFO) ‫الواصل‬‫ي‬ ‫أخيرا‬‫خد‬‫أوال‬ ‫م‬ . Last
number is 1, it is removed first, and so on
done
Sum(1) 1
+ + +
Sum(2) 2 2 2
+ + + + +
Sum(3) 3 3 3 3 3
+ + + + + +
Sum(4) 4 4 4 4 4 4 4
+ + + + + + + + +
Sum(5) 5 5 5 5 5 5 5 5 5
Ans. 1 3 6 10 15
start Step1 Step2 Step3 Step4 Step5 Step6 Step7 Step8 Step9 stop

Write a function using iteration to sun from N to 1
Function Sum (ByVal N as Integer) As Long
Dim S As Long
For i = N To 1 Step -1
S += i
Next
Return s
End Function
For recursion, there should be a stopping rule (here we stop
at 1), the above is written in VB.net as
Function Sum (ByVal N as Integer) As Long
If N = 1 Then Return 1 'Stopping Rule
Return N + Sum (N - 1)
End Function
Write a VB.net functions using recursion to calculate the followings
1. Factorial of a number
Function Factorial (ByVal N As Integer) As Long
If N = 1 or N = 0 Then Return 1 'Stopping Rule
Return N * Factorial (N - 1)
End Function
A fractal is a geometrical figure, but unlike triangles, circles, and
rectangles, fractals can be divided into parts, each of which is a
reduced-size copy of the whole. There are many interesting examples of
fractals. A Sierpinski triangle is a pattern of recursive triangles.
Write a function using recursion to
Calculate M(i) = 1 +
1
2
+
1
3
+
1
4
+
1
5
+ ⋯
1
𝑖
Function M(ByVal i As Integer) As Double
If i = 1 Then Return 1
Return (1 / N) + M(i - 1)
End Function

Calculate M(i) =
1
3
+
2
5
+
3
7
+
4
9
+ ⋯
𝑖
2𝑖+1
If i = 1 Then Return 1 / 3
Return (i / (2 * i + 1)) + M(i - 1)
End Function
Calculate M(i) =
1
2
+
2
3
+
3
4
+
4
5
+ ⋯
𝑖
𝑖+1
If i = 1 Then Return 1 / 2
Return (i / (i + 1)) + M(i - 1)
End Function
Print the characters in a string reversely
Print the digits in an integer reversely
Function P(ByVal S As String) As String
If S.Length = 1 Then Return S
Return S.Substring(S.Length - 1, 1) & P(S.Substring(0, S.Length - 1))
End Function
Occurrences of a specified character in a string) Write a recursive method that
Finds the number of occurrences of a specified letter in a string using the
following
method header:
Sum the digits in an integer using recursion
Function SumDigits(ByVal N As Integer) As Long
If N < 10 Then Return N
Return (N Mod 10) + Sum((N - N Mod 10) / 10)
End Function
Fibonacci series
Public Function Fib(ByVal N As Integer) As Integer
If N <= 2 Then Return 1
Return Fib(N - 1) + Fib(N - 2)
End Function
Call it, explore the Golden Ratio
For i = 1 To 25
T1.Text = T1.Text & i & vbTab & Fib(i) & vbTab & (Fib(i) / Fib(i - 1)).ToString("#.#00") & vbCrLf
Next

PPAASSSSIINNGG PPAARRAAMMEETTEERRSS BBYY RREEFFEERREENNCCEE
1. Write a sub Swap that accept 2 variables x and y as
parameters, then swap them, test it. Print values of x,y
before swap and after swap.
Hint: you should pass parameters by reference
Sub Swap(ByRef x As Integer, ByRef y As Integer)
Dim Temp As Integer
Temp = x
x = y
y = Temp
End Sub
Dim A As Integer = 10, b As Integer = 7
T1.text = "before Swap " & vbcrlf
T1.text = T1.text & "a = " & A & " b = " & b & vbcrlf
Swap (A, b)
T1.text = T1.text & "After Swap " & vbcrlf
T1.text = T1.text & "a = " & A & " b = " & b
OOPPTTIIOONNAALL PPAARRAAMMEETTEERRSS
Write a function that calculate salary tax for an employee, if the
employee is Married, tax is 10% of the salary, if the employee is
single, then tax is 15% of the salary, by default, consider employee
as being Married
Function CalcTax(ByVal salary As Double, Optional ByVal Status As String =
"Married") As Double
If Status = "Married" Then
Return salary * 0.1
Else
Return salary * 0.15
End If
End Function
How to call it?
Dim Tax as double
Tax = CalcTax(100, "Single") tax will be 15
Tax = CalcTax(100, "Married") tax will be 10
You can call it without the second parameter, because if you didn’t specify it, it
is considered by default as Married.
Tax = CalcTax(100) same as Tax = CalcTax(100, "Married") tax will be 10

A nother example with 2 optional parameters
Function CalcTax2(ByVal salary As Double, Optional ByVal Gender As String =
"Male", Optional ByVal Status As String = "Married") As Double
If Status = "Married" Then
If Gender = "Male" Then
Else
End If
Else
If Gender = "Male" Then
Else
End If
End If
End Function
'here we have 3 parameters which are salary, Gender, Status
'How to call it
txtTax.Text = CalcTax2(100) 'use salary only
txtTax.Text = CalcTax2(100, "Male")'use salary and Gender
'use salary, gender and status
txtTax.Text = CalcTax2(100, "Male", "Single")
txtTax.Text = CalcTax2(100, , "Male")'use salary, And status only
OOVVEERRLLOOAADDIINNGG
Overloading means: defining multiple functions with the same name
but with different parameters.
WWHHYY DDOO WWEE NNEEEEDD TTOO UUSSEE OOVVEERRLLOOAADDIINNGG??
it is useful, when the data type of a passed parameter is not the
same, and we need to call the function with different data types,
instead of defining different functions with different names, we use
one function name, but with different parameter data types. For
example, if we have a function
Function abs(ByVal x As Integer) As Integer
Return IIf(x < 0, -x, x)
End Function
If we call is to find the absolute value of -6.254, it will return
6 only, for that, we continue to define the same name for double data
types and other data types
Function abs(ByVal x As Double) As Double
End Function
Function abs(ByVal x As SByte) As SByte
End Function

CCAALLLLIINNGG AA FFUUNNCCTTIIOONN FFRROOMM AANNOOTTHHEERR FFUUNNCCTTIIOONN
Write the correct code to calculate the following formula,
use functions only
Sum the digits in an integer. Write a function that computes the sum
of the digits in an integer.
For example, SumDigits(234) returns 9 (2 + 3 + 4). (Hint: Use the %
operator to extract digits, and the / operator to remove the extracted
digit. For instance, to extract 4 from 234, use 234 % 10 (= 4). To
remove 4 from 234, use 234 / 10 (= 23). Use a loop to repeatedly
extract and remove the digit until all the digits are extracted. Write
a test program that prompts the user to enter an integer and displays
the sum of all its digits.
Function SumDigits(N As Integer) As Integer
Dim Temp As Integer, Remainder As Integer
Temp = N Mod 10
Remainder = (N - Temp) / 10
If Remainder = 0 Then Return Temp
Return Temp + SumDigits(Remainder)
End Function
Another simpler example for any number of digits
Function SumDigits(N As String) As Integer
Dim sum As Integer
For i = 0 To N.Length - 1
sum = sum + Val(N(i))
Next
Return sum
End Function
Call it from click on command button as
T2.Text = SumDigits(T1.Text)

Advanced functions visual Basic .net

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Advanced functions visual Basic .net

Similar to Advanced functions visual Basic .net (20)

More from Mohammad Dwikat

More from Mohammad Dwikat (7)

Recently uploaded

Recently uploaded (20)

Advanced functions visual Basic .net