Podstawy programowania

(2)

dr Jerzy Bartoszek

[e-mail]

[e-mail].p

l

Instrukcja if

If condition Then

[statements]

[ElseIf condition-n Then

[elseifstatements] …]

[Else [elsestatements]]
End If

Przykład instrukcji if

Module Module1
Sub Main()
Dim intInput As Integer

System.Console.WriteLine("Enter an integer…")
intInput =

Val(System.Console.ReadLine())

If intInput = 1 Then
System.Console.WriteLine("Thank you.")
ElseIf intInput = 2 Then
System.Console.WriteLine("That's fine.")
ElseIf intInput = 3 Then
System.Console.WriteLine("Too big.")
Else System.Console.WriteLine("Not a number I know.")
End If

End Sub
End Module

Instrukcja Select Case

Select Case testexpression

[Case expressionlist-n
[statements-n]]
…
[Case Else [elsestatements]]

End Select

Przykład Select Case

Module Module1
Sub Main()

Dim intInput As Integer System.Console.WriteLine("Enter an integer…")
intInput = Val(System.Console.ReadLine())

Select Case intInput

Case 1

System.Console.WriteLine("Thank you.")

Case 2

System.Console.WriteLine("That's fine.")

Case 3

System.Console.WriteLine("OK.")

Case 4 To 7

System.Console.WriteLine("In the range 4 to 7.")

Case Is > 7

System.Console.WriteLine("Definitely too big.")

Case Else

System.Console.WriteLine("Not a number I know.")

End Select

End Sub
End Module

Instrukcja For

For index = start To end [Step

step] [statements]

[Exit For]

[statements]

Next [index]

Przykład For

Module Module1
Sub Main()

Dim intLoopIndex As Integer

For intLoopIndex = 0 To 3

System.Console.WriteLine _

("Hello from Visual Basic")

Next intLoopIndex

End Sub
End Module

Instrukcja Do…Loop

Z warunkiem na początku:

Do [{While | Until} condition ]

[statements]

[Exit Do]

[statements]

Loop

Instrukcja Do…Loop

Z warunkiem na końcu:

Do

[statements]

[Exit Do]

[statements]

Loop

[{While | Until} condition ]

Przykład Do…Loop

Module Module1
Sub Main()

Dim strInput As String

Do Until

UCase(strInput)

= "STOP"

System.Console.WriteLine _
("What should I do?")
strInput = System.Console.ReadLine()
Loop

End Sub
End Module

Instrukcja While

While condition

[statements]

End While

Przykład:

Dim i As Integer = 0
While i<10

System.Console.WriteLine (i)

i +=1

End While

Imports

Imports

System.Console

Module Module1
Sub Main()

WriteLine

("Hello from Visual

Basic")

End Sub
End Module

Operacje na łańcuchach

Module Module1
Sub Main()
Dim strText1 As String = "welcome to visual

basic"

Dim strText2 As String
Dim strText3 As String

strText2 =

UCase

(strText1)

strText3 = strText1.

ToUpper

System.Console.WriteLine(strText2)

System.Console.WriteLine(strText3)

End Sub
End Module

Operacje na łańcuchach cd.

Module Module1
Sub Main()
Dim strText1 As String = "Hey, look here!„
Dim strText2 As String
Dim strText3 As String
strText2 =

Mid(strText1, 6, 4)

strText3 =

strText1.Substring(5, 4)

System.Console.WriteLine(strText2)

System.Console.WriteLine(strText3)

End Sub
End Module

Łańcuchy ↔ liczby

Module Module1
Sub Main()
Dim strText1, strText2 As String =

"1234„

Dim intValue1 As Integer
intValue1 =

Val(strText1)

strText2 =

Str(intValue1)

System.Console.WriteLine(strText2)

End Sub
End Module

Znaki ↔ liczby

• Asc(

"A"

) returns 65

• Chr(65) returns

"A"

Dim OneCharacter As Char =

"

a

pple"

Funkcje matematyczne

Imports System.Math

Module Module1
Sub Main()

System.Console.WriteLine(

Sin

(1.046)

)

End Sub
End Module

Abs, Cos, Exp, Log, Sqr, Round, …

Daty i czas

Imports System.Math
Module Module1
Sub Main()
Dim FirstDate As Date FirstDate =

#12/31/2007#

System.Console.WriteLine("New date: " &

DateAdd(DateInterval.Month, 22, FirstDate)

)

While

TimeString

<

"15:45:00"

End While
Beep()

End Sub
End Module

Wyliczenia

Imports System.Console
Module Module1

Enum Days

Sunday = 1
Monday = 2
…
Friday = 6
Saturday = 7

End Enum

Sub Main()

WriteLine("Friday is day " &

Days.Friday

)

End Sub
End Module

Friday is day 6

Tablice jednowymiarowe

Dim name (max_ind) As type

Przykład:

Dim persons(

4

) As

String

persons(1) = "Bobby"

' persons(

5

) = "David"  Throws

' System.IndexOutOfRange

Exception

Dim Data() = {10, 3, 2}

ReDim

Preserve

persons(10)

Tablice dwuwymiarowe

Dim name (max_ind1, max_ind2) As type

Przykład:

Dim tab(

2, 3

) As

Integer

tab(1, 1) = 15
Dim tabx()() As Integer = { _

New

Integer(4) {},_

New

Integer(1) {},_

New

Integer(2) {} }

tabx(0)(3) = 5