computer programming

1

Computer Programming

Andres, Wen-Yuan Liao

Department of Computer Science and EngineeringDe Lin Institute of Technology

[email protected]://www.cse.dlit.edu.tw/~andres

mailto:[email protected]

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Chapter 4

Numeric Types and Expressions

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Chapter 4 Topics

Constants of Type Integer and Double Evaluating Arithmetic Expressions Increment and Decrement Operators Implicit Type Conversion and Explicit Type

Casting Calling a Value-Returning Method Using VB .NET Math class methods String Operations Length, IndexOf, Substring

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4.1 VB .NET Primitive Data Types4.1 VB .NET Primitive Data Types

primitive

Integral

Boolean

Byte Char Short Integer Long Single Double

Floating Point

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VB .NET Data TypesVB .NET Data Types

Reference

Array Interface Class

primitive

Integral Boolean

Byte Char Short Integer Long Single Double

Floating Point

VB .NET Data Types

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Primitive and Reference Types

letter

Dim letter As Char

Dim title As String

Dim bookName As String

letter = "J"

title = " Programming with VB.NET "

bookName = title

7


letter

title

Dim letter As Char

Dim title As String


letter = "J"


bookName = title

8


letter

title

bookName

Dim letter As Char

Dim title As String


letter = "J"


bookName = title

9


letter

title

bookName

Dim letter As Char

Dim title As String


letter = "J"


bookName = title

"J"

10


letter

title

bookName

2002

"Programming with VB.NET "

Memory Location 2002

"J"

Dim letter As Char

Dim title As String


letter = "J"


bookName = title

11

Dim letter As Char

Dim title As String

Dim book As String

letter = "J"


book = title


letter

title

bookName

2002

2002



"J"

12


Dim letter As Char

Dim title As String

Dim book As String

letter = "J"


bookName = title

letter

title

bookName

2002

2002



"J"

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4.2Primitive Data Types in VB .NET

Integral Types can represent whole numbers and their

negatives when declared as Short, Integer, or Long

can represent single characters when declared as Char

Floating Point Types represent real numbers with a decimal point declared as Single, or Double

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Samples of VB .NET Data Values

Integer sample values 4578 -4578 0

Double sample values95.274 95. .265

Char sample values

‘B’ ‘d’ ‘4’ ‘?’ ‘*’

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Integral Types

Type Size in Bits Minimum Value to Maximum Value

Byte 8 -128 to 127

Short 16 -32,768 to 32,767

Integer 32 -2,147,483,648 to 2,147,483,647

Long 64 -9,223,372,036,854,775,808 to

+9,223,372,036,854,775,807

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Sizes of Integral VB .NET Types

Byte 8 bits

Short 16 bits

Integer 32 bits

Long 64 bits

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Using one byte ( = 8 bits ),

HOW MANY DIFFERENT NUMBERS CAN BE REPRESENTED USING 0’s and 1’s?

Each bit can hold either a 0 or a 1. So there are just two choices for each bit, and there are 8 bits.

2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 = 28 = 256

0 1 1 0 0 0 1 1

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Similarly, using two bytes (= 16 bits),

216 = 65536

DIFFERENT NUMBERS CAN BE REPRESENTED. If we wish to have only one number representing the

integer zero, and half of the remaining numbers positive, and half negative, we can obtain the 65,536 numbers in the range below :

-32768 . . . . 0 . . . . 32767

0 1 0 0 1 0 1 00 1 1 0 0 0 1 1

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Exponential (Scientific) Notation

2.7E4 means 2.7 x 10 4 =

2.7000 =

27000.0

2.7E-4 means 2.7 x 10 - 4 =

0002.7 =

0.00027

Type Size in Bits Range of Values

Single 32 +1.4E - 45 to

+3.4028235E+38

Double 64 +4.9E - 324 to

+1.7976931348623157E+308

Floating Point Types

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More About Floating Point Types

Floating-point types have an integer part and a fractional part, with a decimal point in between. Either the integer part or the fractional part, but not both, may be missing.

EXAMPLES 18.4 500. .8 -127.358

Alternatively, floating point values can have an exponent, as in scientific notation. The number preceding the letter E doesn’t need to include a decimal point.

EXAMPLES 1.84E1 5E2 8E-1 -.127358E3

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4.3 Declarations for Numeric Types

Named constant declarationConst PI As Double =3.14159

Const E As Single = 2.71828F

Const MAX_TEMP As Long = 1000000000L

Const MIN_TEMP As Integer = -273

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Variable Declarations

Dim student As Integer

Dim sumOfScore As Integer

Dim sumOfSquare As Long

Dim average As Double

Dim deviation As Simgle

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4.4 What is an Arithmetic Expression?

An arithmetic expression is a valid arrangement of variables, constants, operators and parentheses.

An expression can be evaluated to compute a value of a given type.

The value of the expression

9.3 * 4.5 is 41.85

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Some VB .NET Operators

Operator Description ( ) Parentheses

+ Positive

- Negative

* Multiplication

/ Division % Modulus

(remainder)

+ Addition

- Subtraction

= Assignment

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Operator

Operand, operator Unary operator

An operator that has just one operand. + (positive), -(negative)

Binary operator An operator that has two operand. + (Addition), - (Subtraction), *, /, %, =

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Division Operator

The result of the division operator depends on the type of its operands.

If one or both operands has a floating type, the result is a floating point type (float or double). Otherwise, the result is an integral type.

EXAMPLES

11 / 4 has value 2

11.0 / 4.0 has value 2.75

11 / 4.0 has value 2.75

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Modulus Operator

The modulus operator % when used with integer type operands has an integer type result.

Its result is the integer type remainder of an

integer division.

EXAMPLE

11 % 4 has value 3 because

)4 11

2 and Remainder = ?

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' *************************************************' FreezeBoil program' This program computes the midpoint between' the freezing and boiling points of water' *************************************************

Imports System.ComponentModel 'Import component handlingImports System.Drawing 'Import graphicsImports System.WinForms 'Import forms, event

'handling types

Public Class Form1 'Create form for output Inherits System.WinForms.Form Const FREEZE_PT As Double = 32 'Freezing pt of water Const BOIL_PT As Double = 212 'Boiling pt of water Dim avgTemp As Double 'Holds the result of

'averaging FREEZE_PT and'BOIL_PT

Public Sub New() MyBase.New()

Form1 = Me

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'This call is required by the Win Form Designer InitializeComponent() lblFreeze.Text = "Water freezes at " & FREEZE_PT lblFreeze.text = lblFreeze.Text & " and boils at “ & _

BOIL_PT & " degrees." avgTemp = FREEZE_PT + BOIL_PT avgTemp = avgTemp / 2

lblFreeze.Text = lblFreeze.Text & "Halfway between is"_& avgTemp & "degrees."

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4.5 Compound VB .NET Operators

Precedence Operator Description Higher ( ) Parentheses

+ Positive

- Negative

* Multiplication

/ Division % Modulus

(remainder)

+ Addition

- Subtraction

Lower = Assignment

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Precedence

Higher Precedence determines which

operator is applied first in an expression

having several operators.

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Associativity

Left to right Associativity means that in an expression having 2 operators with the same priority, the left operator is applied first. (left to right)

In VB .NET, the binary operators * , / , % , + , - are all left associative.

Expression 9 - 5 + 1 means ( 9 - 5 ) + 1not 9 – (5 +1 ) 4 + 1

5

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VB .NET Operator Precedence(highest to lowest)

Operator Associativity

. ( ) ( args ) Left to right

unary: + - Right to left

New ( type ) Right to left

* / % Left to right

+ - Left to right

= Right to left

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7 * 10 - 5 % 3 * 4 + 9means (7 * 10) - 5 % 3 * 4 + 9

70 - 5 % 3 * 4 + 9 70 - (5 % 3) * 4 + 9

70 - 2 * 4 + 9 70 - ( 2 * 4 ) + 9 70 - 8 + 9

( 70 - 8 ) + 9 62 + 9

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Evaluate the Expression

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Parentheses

Parentheses can be used to change the usual order. Parts in ( ) are evaluated first. Evaluate (7 * (10 - 5) % 3) * 4 + 9

( 7 * 5 % 3 ) * 4 + 9 ( 35 % 3 ) * 4 + 9

2 * 4 + 9 8 + 9

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More VB .NET Operators

Dim age As Integer

age = 8

age = age + 1

age

9

8

age

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Variable = Expression

First, Expression on right is evaluated.

Then the resulting value is stored in the memory location of Variable on left.

NOTE: An automatic type conversion occurs after evaluation but before the value is stored if the types differ for Expression and Variable

Assignment Operator Syntax

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What value is stored?

Dim a As Double

Dim b As Double

a = 8.5

b = 9.37

a = b

a

b

a

b

8.5

9.37

?

?

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What value is stored?

Dim a As Double

Dim b As Double

a = 8.5

b = 9.37

a = b

a

b

a

b

8.5

9.37

9.37

9.37

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What is stored?

?

Dim someDouble As Single

someDouble = 12 ' implicit type conversion

someDouble

12.0

someDouble

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What is stored?

? Dim someInt As Integer

someInt someInt = 4.8 ' implicit type conversion

someInt

4

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Implicit type conversion occurs . . .

Whenever values of different data types are used in:

1. arithmetic expressions

2. assignment operations

TWO RULES APPLY . . .

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Type conversion

The implicit (automatic) conversion of a value from one data type to another.

Widening conversion A type conversion that dose not result in a loss of

information.

narrowing conversion A type conversion that may result in a loss of some

information, as in converting a value of type Double to Single.

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A widening conversion . . .

Is a type conversion that does not result in a loss of information. Specifically, for mixed type expressions using both integer and floating-point type values:

Step 1. The integer value is temporarily converted to a

floating-point value.

Step 2. The operation is performed.

Step 3. The result is a floating-point value.

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Is a type conversion that may result in a loss of information.

FOR EXAMPLE, 98.6 98

temperature number

Dim temperature As Double = 98.6

Dim number As Integer

number = temperature 'loss occurs

A narrowing conversion . . .

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CInt converts its argument to an Integer type.

CLng converts its argument to a Long type.

CSng converts its argument to a Single type.

CDbl converts its argument to a Double type.

Type Conversation is Explicit Conversion of Type

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CInt(4.8) has value 4

CDbl(5) has value 5.0

CDbl(7/4) has value 1.0

CDbl(7) / CDbl(4) has value 1.75

Type Conversation is Explicit Conversion of Type

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Some Expressions

Dim age As Integer

EXAMPLE

someDouble = CDbl(3 * someInt + 2)

someInt = CInt(5.2 / someDouble – 2.0)

someSingle = someInt + 8

someSingle = CSng( someInt + 8 ) CDbl ( 4 / 8 ) 0.0

CDbl ( 4 ) / 8 0.5

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What values are stored?

Dim loCost As Double

Dim hiCost As Double

loCost = 12.342

hiCost = 12.348

loCost = CDbl (CInt (loCost * 100.0 + 0.5)) / 100.0

hiCost = CDbl (CInt (hiCost * 100.0 + 0.5)) / 100.0

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Values Rounded to 2 Decimal Places

12.34

hiCost

12.35

loCost

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4.6 Method Call

A method call temporarily transfers control to the called method’s code to perform a task.

When the method’s code has finished executing, control is transferred back to the calling block.

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Where are VB .NET methods?

located in class libraries

OR

written by programmers

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Write a VB .NET expression . . .

To find the larger of myAge and yourAge and place it in variable older

Dim older As Integer

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To find the larger of myAge and yourAge and place it in variable older

Dim older As Integer

. . .

older = Math.Max ( myAge, yourAge )

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To find the square root of b2 - 4ac and place it in variable d.

Dim a, b, c, d As Double

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To find the square root of b2 - 4ac and place it in variable d.

Dim a, b, c, d As Double

. . .

d = Math.Sqrt ( b * b - 4.0 * a * c )

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Some Math class methods

Math.Abs ( x ) Math.Abs( -9.8 ) is 9.8' absolute value of x

Math.Sqrt( x ) Math.Sqrt( 9.0 ) is 3.0' square root of a non-negative x

Math.Log ( x ) Math.Log( 1.0 ) is 0' natural (base e) logarithm of x

Math.Max ( x, y ) Math.Max( 2.5, 6.7) is 6.7

' larger value of x and y

Math.Pow ( x, y ) Math.Pow( 9, 0.5 ) is 3.0' x raised to the power y

A method call uses the name of the method followed by ( ) enclosing a list of parameters.

Console.WriteLine ("Done")

older = Math.Max (myAge, your Age)

number = Math.Sqrt (456.34)

A method call temporarily transfers control to the called method to perform its task.

Method Calls

Two Kinds of Methods

Always is called as part of an expression. Does some task.

Returns a value that takes its place in the expression.

Always is called as a separate statement.

Does some task.

Never returns a value to its caller.

Value-Returning Non-value Returning

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ObjectName.MethodName( Parameter List )

The parameter list is used to communicate values to the method by passing information.

The parameter list can contain 0, 1, or more parameters, separated by commas, depending on the method.

Method Call Syntax

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4.7 Additional String Operations

Length method Method Length returns an Integer

value that equals the number of characters in the string.

You must use dot notation and parentheses in the call to method Length.

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What value is returned?

' Using methods Length

Dim firstName As String

Dim fullName As StringDim len As Ineger

firstName = " Alexandra “len = firstName.Length( ) fullName = firstName & “Jones”len = fullName.Length( )

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IndexOf method

Method IndexOf searches a string to find a

particular substring, and returns an Integer value that is the beginning position for the first

occurrence of that substring within the string.

The substring argument can be a literal String,

a String expression, or a Char value.

If the substring could not be not found, method IndexOf returns value -1.

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' Using methods IndexOf

Dim phrase As String Dim position As Integer phrase = “The dog and the cat "

position = phrase.IndexOf(“the” ) position = phrase.IndexOf(“rat” )

Dim theString As String theString = “Abracadaba "

position = theString.IndexOf(“a”c )

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' Using methods IndexOf

Dim str1 As String Dim str2 As String str1 = “Programming and Problem Solving "str2 = “gram"

str1.IndexOf(“and” ) str1.IndexOf(“Programming” ) str2.IndexOf(“and” ) str1.IndexOf(“Pro” ) str1.IndexOf(“ro” & str2 ) str1.IndexOf(“pr” & str2 ) str1.IndexOf(“ ” )

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Substring method

Method Substring returns a particular substring of a string, but does not change the string itself.

The first parameter is an Integer that specifies a starting position within the string.

The second parameter is an Integer that is 1 more than the ending position of the substring.

Positions of characters within a string are numbered starting from 0, not from 1.

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' Using methods Length, IndexOf, Substring

Dim myString As String = "Programming and Problem Solving "

myString.Substring ( 0, 7) myString.Substring ( 7, 8) myString.Substring ( 11, 1)

myString.Substring ( 24, 7)myString.Substring ( 24, 1)

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' Using methods Length, IndexOf, Substring

Dim stateName As String = " Mississippi "

stateName.Length( ) value 11

stateName.IndexOf ( " is ") value 1

stateName.Substring( 0, 4 ) value “Miss”

stateName.Substring( 4, 6 ) value “is”

stateName.Substring( 9, 11 ) value “pi”

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Map Measurement Case Study

You want a program to determine walking distances between 4 sights in the city.

Your city map legend says one inch on the map equals 1/4 mile in the city.

You use the measured distances between 4 sights on the map.

Display the walking distances (rounded to the nearest tenth) between each of the 4 sights.

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'******************************************************* ' Walk program' This program computes the mileage (rounded to nearest' tenth of mile) for each of 4 distances, given the' measurements on a map with scale of 1 in = 0.25 mile' *******************************************************

Imports System.ComponentModelImports System.DrawingImports System.WinForms

Public Class Form1Inherits System.WinForms.Form

VB .NET Case Study Program

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VB .NET Case Study Continued

Const DISTANCE1 As Double = 1.5 ‘Measurement for 1st distance Const DISTANCE2 As Double = 2.3 'Measurement for 2nd distance Const DISTANCE3 As Double = 5.9 'Measurement for 3rd distance Const DISTANCE4 As Double = 4R 'Measurement for 4th distance Const MAP_SCALE As Double = 0.25 'Map SCALE

Dim totMiles As Double 'Total of rounded mileage Dim miles As Double 'An individual rounded mileage

Public Sub New()My Base.NewForm1 = MeInitializeComponent()

totMiles = 0R

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'Compute and display miles for each distance on the map'Output will not display .0 amounts

miles = CDbl(CInt(DISTANCE1 * MAP_SCALE * 10R + 0.5) / 10R) lblDistance1.Text = "For a measurement of " & DISTANCE1 & _

" the first distance is " & miles _ & " mile(s) long. "

totMiles = totMiles + miles miles = CDbl(CInt(DISTANCE2 * MAP_SCALE * 10R + 0.5) / 10R) lblDistance2.Text = "For a measurement of " & DISTANCE2 & _

" the second distance is " & miles & _ " mile(s) long."



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totMiles = totMiles + miles lblTotMiles.Text = "Total mileage for the day is " & _

totMiles & " miles." End Sub

'Form overrides dispose to clean up the component list. Overrides Public Sub Dispose()

MyBase.Disposecomponents.Dispose

End Sub

#Region " Windows Form Designer generated code "

#End Region

End Class

computer programming

Documents

title letter title bookname

vbnet bookname

stringdim bookname

chardim title

reference typesdim letter

jdim letter

numeric types

vbnet memory location