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Chapter 3. The General Structure of Ada Programs. General Form of an Ada Program. With package1; With package2; . . . With packagen; Procedure pname IS - - comments declaration of variables, constants, etc. . . Begin Program statement; . . . Program statement; End;. - PowerPoint PPT Presentation
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Chapter 3Chapter 3
The General Structure of Ada The General Structure of Ada ProgramsPrograms
General Form of an Ada General Form of an Ada ProgramProgram
With package1;With package1;
With package2;With package2;
. . . . . .
With packagen;With packagen;
Procedure Procedure pname pname ISIS
- - comments- - comments
declaration of variables, constants, etc. . . declaration of variables, constants, etc. . .
BeginBegin
Program statement;Program statement;
. . .. . .
Program statement;Program statement;
End;End;
With clauseWith clause
To inform the compiler for a package used To inform the compiler for a package used in the program in the program
at least one “with” clause in Ada programat least one “with” clause in Ada program package for Text Input and Outputpackage for Text Input and Output
• WITH Ada.Text_IO;
package for Integer Text Input and Outputpackage for Integer Text Input and Output• WITH Ada.Integer_Text_IO;
package for Floating Text Input and Outputpackage for Floating Text Input and Output• WITH Ada.Float_Text_IO;
Identifiers or namesIdentifiers or names
Begin with a letterBegin with a letter Consist of only letters, digits, and underscoresConsist of only letters, digits, and underscores Cannot use two or more underscore Cannot use two or more underscore
characters in successioncharacters in succession Cannot use an Ada reserved word or pre-Cannot use an Ada reserved word or pre-
defined identifier as an identifier defined identifier as an identifier
Pick meaningful names for identifiersPick meaningful names for identifiers no restriction on the length of an identifierno restriction on the length of an identifier
Type of dataType of data
CharacterCharacter IntegerInteger FloatFloat
Example-1Example-1Displaying Initials ProgramDisplaying Initials Program
WITH Ada.Text_IO;PROCEDURE Hello_Initials IS-------------------------------------------------------
-------| Requests, then displays, user's first and last
initials.--|-------------------------------------------------------
-----
Initial1 : Character; -- objects that hold initials Initial2 : Character;
Cont. of example-1Cont. of example-1
BEGIN -- Hello_Initials-- Prompt for (request user to enter) user's initials Ada.Text_IO.Put(Item => "Enter your two initials> "); Ada.Text_IO.Get(Item => Initial1); Ada.Text_IO.Get(Item => Initial2);
-- Display user's initials, with a greeting Ada.Text_IO.Put(Item => "Hello "); Ada.Text_IO.Put(Item => Initial1); Ada.Text_IO.Put(Item => Initial2); Ada.Text_IO.Put(Item => ". Enjoy studying Ada!"); Ada.Text_IO.New_Line;
END Hello_Initials;
Reserve Words and Reserve Words and IdentifiersIdentifiers
Reserve WordsReserve Words
With With
ProcedureProcedure
ISIS
BeginBegin
END END
Predefined IdentifiersPredefined Identifiers
Ada.Text_IOAda.Text_IO
PutPut
New_LineNew_Line
CharacterCharacter
GetGet
Input and Output Input and Output
package for Text Input and Outputpackage for Text Input and Output• WITH Ada.Text_IO;
package for Integer Text Input and package for Integer Text Input and OutputOutput• WITH Ada.Integer_Text_IO;
package for Floating Text Input package for Floating Text Input and Outputand Output• WITH Ada.Float_Text_IO;
Read Float NumberRead Float Number
To read a float number into identifier To read a float number into identifier “Inches”“Inches”
WITH Ada.Float_Text_IO;
Inches : Float;Inches : Float;
Ada.Ada.FloatFloat_Text._IO._Text._IO.GetGet ( Item => Inches); ( Item => Inches);
Read Integer NumberRead Integer Number
To read an integer number into identifier To read an integer number into identifier “Age”“Age”
WITH Ada.Integer_Text_IO;
Age : Integer;Age : Integer;
Ada.Ada.IntegerInteger_Text._IO._Text._IO.GetGet ( Item => Age); ( Item => Age);
Read CharacterRead Character
To read a character into identifier To read a character into identifier “Initial1”“Initial1”
WITH Ada.Text_IO;
Initial1 : Character;Initial1 : Character;
Ada.Text._IO.Ada.Text._IO.GetGet ( Item => Initial1); ( Item => Initial1);
Write Float NumberWrite Float Number
To write a float number into identifier To write a float number into identifier “Inches”“Inches”
WITH Ada.Float_Text_IO;
Inches : Float;Inches : Float;
Ada.Ada.FloatFloat_Text._IO._Text._IO.PutPut ( Item => Inches); ( Item => Inches);
Integer and Character Integer and Character outputoutput
WITH Ada.Integer_Text_IO;
Age : Integer;Age : Integer;
Ada.Ada.IntegerInteger_Text._IO._Text._IO.PutPut ( Item => Age); ( Item => Age);
WITH Ada.Text_IO;
Initial1 : Character;Initial1 : Character;
Ada.Text._IO.Ada.Text._IO.PutPut ( Item => Initial1); ( Item => Initial1);
Example-2Example-2Displaying the User’s NameDisplaying the User’s Name
WITH Ada.Text_IO;PROCEDURE Hello_Name IS-------------------------------------------------------
-------------------| Requests, then displays, user's name--| -------------------------------------------------------
-----------------
FirstName: String(1..10); -- object to hold user's name
Cont. of example 2Cont. of example 2
BEGIN -- Hello_Name -- Prompt for (request user to enter) user's name Ada.Text_IO.Put (Item => "Enter your first name, exactly 10 letters."); Ada.Text_IO.New_Line; Ada.Text_IO.Put (Item => "Add spaces at the end if it's shorter.> "); Ada.Text_IO.Get(Item => FirstName); -- Display the entered name, with a greeting Ada.Text_IO.Put(Item => "Hello "); Ada.Text_IO.Put(Item => FirstName); Ada.Text_IO.Put(Item => ". Enjoy studying Ada!"); Ada.Text_IO.New_Line;END Hello_Name;
Constant Object DeclarationConstant Object Declaration
FormForm
some_constantsome_constant : CONSTANT : CONSTANT type type :=:= valuevalue;;
ExampleExample
Pi : CONSTANT Float := 3.14159;Pi : CONSTANT Float := 3.14159;
Assignment StatementAssignment Statement
Result_Variable := expression;Result_Variable := expression;
ExampleExample
X := Y + Z + 2.0;X := Y + Z + 2.0;
X := X +1;X := X +1;
Example-3Example-3Converting Inches to Converting Inches to CentimetersCentimeters
WITH Ada.Text_IO;WITH Ada.Float_Text_IO;PROCEDURE Inch_to_CM IS-------------------------------------------------------
-------------------| Converts inches to centimeters-------------------------------------------------------
----------------- CMPerInch : CONSTANT Float := 2.54; Inches : Float; Centimeters : Float;
Cont. of example-3Cont. of example-3
BEGIN -- Inch_to_CM-- Prompt user for value in inches Ada.Text_IO.Put (Item => "Enter a length in inches> "); Ada.Float_Text_IO.Get (Item => Inches); -- Compute equivalent value in centimeters Centimeters := CMPerInch * Inches; -- Display result Ada.Text_IO.Put (Item => "That equals "); Ada.Float_Text_IO.Put (Item => Centimeters); Ada.Text_IO.Put (Item => " centimeters"); Ada.Text_IO.New_Line;
END Inch_to_CM;
New Line ProcedureNew Line Procedure
FormForm
Ada.Text_IO.New_Line ( Spacing => positive Ada.Text_IO.New_Line ( Spacing => positive number);number);
ExampleExample
Ada.Text_IO.New_Line ( Spacing =>3);Ada.Text_IO.New_Line ( Spacing =>3);
Put Procedure ( Integer) with Put Procedure ( Integer) with WidthWidth
Ada.Integer_Text._IO.Put Ada.Integer_Text._IO.Put
( Item => variable , ( Item => variable , Width => field widthWidth => field width););
ExampleExample
Ada.Integer_Text._IO.Put Ada.Integer_Text._IO.Put
( Item =>How_Long , ( Item =>How_Long , Width => 5Width => 5););
See page 93 for more examples See page 93 for more examples
Put Procedure ( Float) with Fore, Put Procedure ( Float) with Fore, Aft, ExpAft, Exp
Ada.Float_Text._IO.Put Ada.Float_Text._IO.Put
( Item => variable ,( Item => variable , Fore Fore =>=> n n,, Aft Aft =>=> n n, Exp, Exp =>=> n n ););
ExampleExample
Ada.Float_Text._IO.Put Ada.Float_Text._IO.Put
( Item =>Centimeter , Fore => 5, Aft,=> 2, Exp => ( Item =>Centimeter , Fore => 5, Aft,=> 2, Exp => 0);0);
77.47 rather than 7.74700E+0177.47 rather than 7.74700E+01
See Page 94 for more examplesSee Page 94 for more examples
Data Types and Data Types and ExpressionsExpressions
IntegerInteger• NaturalNatural and and PositivePositive are subtypes of are subtypes of
Integer.Integer.
REM operationREM operation• 3 REM 2 is 13 REM 2 is 1• 17 REM 3 is 217 REM 3 is 2• 2 REM 3 is 22 REM 3 is 2
ExponentiationExponentiation• X ** 2 is 9 ( if X is 3 )X ** 2 is 9 ( if X is 3 )• X ** 3 is 27 ( if X is 3 )X ** 3 is 27 ( if X is 3 )
• Y ** 2 is 1.44 ( if Y is 1.2 )Y ** 2 is 1.44 ( if Y is 1.2 )• Y ** 3 is 1.728 ( if Y is 1.2)Y ** 3 is 1.728 ( if Y is 1.2)• Y ** 1.5 is not allowed . The power Y ** 1.5 is not allowed . The power
must be an integer.must be an integer.
Float LiteralsFloat Literals
A Float literal is a number that begins A Float literal is a number that begins with a digit contains a decimal point.with a digit contains a decimal point.
ExampleExample
3.141593.14159 0.0005 0.0005 1234.01234.0 15.0E-05 15.0E-05
-1.2E+6-1.2E+6 1.15E-31.15E-3 2.3E22.3E2
But notBut not
150150 .1234.1234 12345.12345. 15E-0315E-03
12.5E.312.5E.3 -.123E3-.123E3
ExpressionExpression
Precedence Rules ( more in chap 8)Precedence Rules ( more in chap 8) Parentheses, multiplication, division, Parentheses, multiplication, division,
addition and subtractionaddition and subtraction
A.A. W := Z * X + Y;W := Z * X + Y;
B.B. W := Z * ( X + Y) ;W := Z * ( X + Y) ;
if X=1, Y=2 and Z= 3, then if X=1, Y=2 and Z= 3, then
A will get the result “5” and B will be “9”.A will get the result “5” and B will be “9”.
Example -4 Coin Collection Example -4 Coin Collection ProgramProgram
WITH Ada.Text_IO;WITH Ada.Integer_Text_IO;PROCEDURE Coin_Collection IS--------------------------------------------------------------
------------| Finds the value of a coin collection,--| given pennies and nickels--------------------------------------------------------------
---------- Pennies : Natural; -- input - number of pennies Nickels : Natural; -- input - number of nickels Dollars : Natural; -- output - value in dollars Cents : Natural; -- output - value in cents TotalCents : Natural;
Cont - 1 for Example 4Cont - 1 for Example 4
BEGIN -- Coin_Collection
-- prompt user for number of nickels and pennies Ada.Text_IO.Put (Item => "How many nickels do you have? "); Ada.Integer_Text_IO.Get (Item => Nickels); Ada.Text_IO.Put (Item => "How many pennies do you have? "); Ada.Integer_Text_IO.Get (Item => Pennies); Ada.Text_IO.New_Line; -- compute total value in cents TotalCents := 5 * Nickels + Pennies; -- find the value in dollars and change Dollars := TotalCents / 100; Cents := TotalCents REM 100;
Cont - 2 for Example 4Cont - 2 for Example 4
-- display the value in dollars and change Ada.Text_IO.Put (Item => "Your collection is worth
"); Ada.Integer_Text_IO.Put (Item => Dollars, Width =>
1); Ada.Text_IO.Put (Item => " dollars and "); Ada.Integer_Text_IO.Put (Item => Cents, Width => 1); Ada.Text_IO.Put (" cents."); Ada.Text_IO.New_Line;
END Coin_Collection;
