Chap 5 Control Structure

1
Chap 5Control Structure

• Boolean Expression and
• the IF Statement

2
IF Statement (One Alternative)

• IF condition THEN
• statement sequence T
• END IF
• - - - - - - - - - - - - - - - - - - - - - - - -
  - - - - - - - - - - - - - -
• if condition is true then
• execute the statement sequence T

3
Example for IF statement

• IF Xgt18 THEN
• Adult Adult 1
• END IF

4
IF Statement (Two Alternative)

• IF Condition THEN
• statement sequence T
• ELSE
• statement sequence F
• END IF
• - - - - - - - - - - - - - - - - - - - - - - - - -
  - - - - - - - - - - - - - - -

5
IF THEN ELSE

• if condition is true then execute statement
  sequence T and statement sequence F is skipped
• otherwise, statement sequence F is executed and
  statement sequence F is skipped

6
Example

• IF X gt 0.0 THEN
• Ada .TEXT_IO.Put (Item gt X is Positive )
• ELSE
• Ada .TEXT_IO.Put (Item gt X is Negative)
• END IF

7
Boolean Expression

• variable relational operator variable
• e.g.
• X gt Y
• variable relational operator constant
• e.g.
• X gt 0.0

8
Relational Operator

• lt less or equal to
• lt less than
• gt greater than or equal to
• gt greater than
• equal to
• / not equal to

9
Let us test how much we understand

• Suppose x, y , z integer
• if x 2
• y 5
• z 0
• Find the value for z after executing
• IF x gt y THEN
• z z 1
• ELSE
• z z 2
• END IF

10
The Multiple-AlternativeIF Statement

• IF condition-1 THEN
• statement sequence 1
• ELSIF condition-2 THEN
• statement sequence 2
• . . . .
• ELSIF condition-k THEN
• statement sequence k
• ELSE
• statement sequence n
• END IF

11
Example

• IF Ngt 0 THEN
• Ada.Text_IO.Put (Itemgt Positive)
• ELSIF N0 THEN
• Ada.Text_IO.Put (Item gt Zero)
• ELSE
• Ada.Text_IO.Put (Item gt Negative)
• END IF

12
More Example

• Exam Score Grade
• ---------------- --------
• 90 and above A
• 80-89 B
• 70-79 C
• 60-69 D
• below F

13
Grade problem

• - - - grade assignment
• IF score gt 90 THEN
• Ada.Text_IO.Put ( Item gt You got,
  A)
• ELSIF score gt 80 THEN
• Ada.Text_IO.Put ( Item gt You got,
  B)
• ELSIF score gt 70 THEN
• Ada.Text_IO.Put ( Item gt You got, C)
• ELSIF score gt 60 THEN
• Ada.Text_IO.Put ( Item gt You got, D)
• ELSE
• Ada.Text_IO.Put ( Item gt You got, F)
• END IF

14
Think about this problem

• if you speed up in 35 mile limit zone
• Fees are as follow
• 20 for under 50 mph,
• 40 for under 75 mph and
• 60 for more than 75 mph

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Is This Answer A Ok?

• IF Speed gt 35 THEN
• Fee 20.00
• ELSIF Speed gt50 THEN
• Fee 40.00
• ELSIF Speed gt75 THEN
• Fee 60.00
• END IF

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Or Is This Answer B OK ?

• IF Speed gt 75 THEN
• Fee 60.00
• ELSIF Speed gt 50THEN
• Fee 40.00
• ELSIF Speed gt 35THEN
• Fee 20.00
• END IF

17
Using Adas Math Library

• With Ada.Numerics.Elementary_Functions
• Example
• Subtype NonNegFloat IS FLOAT Range 0.0 . .
  FloatLast
• First NonNegFloat
• FirstAda.Numerics.Elementary_Functions.Sqrt(Xgt
  First)

18
Writing Functions

• Function Specifications
• In Chap 4, we found that
• Function Year (Date Time) Return Year_Number
• Function Month (Date Time) Return Month_Number
• Function Day (Date Time) Return Day_Number

19
Functions

• Function Specification
• Function Body

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FUNCTION SPECIFICATION

• FUNCTION Func_Name ( formal parameter)
• RETURN result _type
• Example
• FUNCTION Maximum (VaL1, Val2 Integer)
• RETURN Integer

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FORM for FUNCTION BODY

• FUNCTION Func_Name (formal parameter)
• RETURN result_type IS local declaration
  section
• BEGIN
• statement sequence
• END Func_Name

22
Example for FUNCTION BODY

• FUNCTION Square (Num Integer) RETURN Integer
  IS
• Result Integer
• BEGIN
• Result Num Num
• RETURN Result
• END Square

23
Maximum Function

• FUNCTION Maximum ( VaL1, VaL2 Integer)
  RETURN
  Integer IS Result Integer
• BEGIN
• IF VaL1 gt VaL2 THEN
• Result VaL1
• ELSE
• Result VaL2
• End IF
• RETURN Result
• END Maximum

24
Calling A Function

• Score1 78
• Score2 89
• Larger Maximum( VaL1gt Score1 ,VaL2 gt Score2
  )
• What is the value of Large ?

25
Example Program with Function

• With Ada.Text_IO
• With Ada.Integer_Text_IO
• Procedure Large Is
• - - This program is to find the maximum value of
  given two numbers
• - -
• - - Declare Variables
• Num1, Num2, Large Integer

26
Cont. Of Large_Small Program

• - - - - - - - -Function Specification
• FUNCTION Maximum (VaL1, Val2 Integer) Return
  Integer
• - - - - - - - - Function Body
• FUNCTION Maximum ( VaL1, VaL2 Integer)
  RETURN Integer IS Result Integer
• BEGIN
• IF VaL1 gt VaL2 THEN
• Result VaL1
• ELSE
• Result VaL2
• End IF
• RETURN Result
• END Maximum

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Cont..

• Begin
• Ada.Text_IO.Put (Item gt" Give Number 1 ")
• Ada.Integer_Text_IO.Get(Item gt Num1)
• Ada.Text_IO.New_Line
• Ada.Text_IO.Put (Item gt" Give Number 2 ")
• Ada.Integer_Text_IO.Get(Item gt Num2)
• Ada.Text_IO.New_Line
• Large Maximum( VaL1gtNum1, VaL2gtNum2)
• Ada.Text_IO.Put (Item gt " Large Number is ")
• Ada.Integer_Text_IO.Put(Item gt Large)
• Ada.Text_IO.New_Line
• End Large

28
Writing Package

• Package Specification
• Package Body

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Package Specification

• PACKAGE Pack_Name IS
• list of specifications of resourses
• provided by the package
• END Pack_Name

30
Example forPackage Specification

• PACKAGE Min_Max IS
• FUNCTION Minimum ( VaL1 , VaL2 Integer)
  RETURN Integer
• FUNCTION Maximum ( VaL1 , VaL2
  Integer)RETURN Integer
• END Min_Max

31
Form for Package Body

• PACKAGE BODY Pack_Name IS
• sequence of function and procedure bodies
  implementing the resources listed in the package
  specification for Pack_Name
• END Pack_Name

32
Example For Package Body

• PACKAGE BODY Min_Max IS
• - - - - - -
• - - bodies of functions for Min_Max package
• - - - - - -
• FUNCTION Minimum ( VaL1, VaL2 Integer)
  RETURN Integer IS Result Integer
• BEGIN
• IF VaL1 ltVaL2 THEN
• Result VaL1
• ELSE
• Result VaL2
• End IF
• RETURN Result
• END Minimum

33
Cont Of The Min_Max PACKAGE BODY

• FUNCTION Maximum ( VaL1, VaL2 Integer)
  RETURN Integer IS Result Integer
• BEGIN
• IF VaL1 gt VaL2 THEN
• Result VaL1
• ELSE
• Result VaL2
• End IF
• RETURN Result
• END Maximum
• END Min_Max

34
Calling Functions from Min_Max Package

• With Ada.Text_IO
• With Ada.Integer_Text_IO
• With Min_Max - - - -
  - our new package
• Num1, Num2, Large, Small Integer
• Large Min_Max.Maximum( VaL1gtNum1,
  VaL2gtNum2)
• Small Min_Max.Minimum( VaL1gtNum1,
  VaL2gtNum2)