Structured Types - Problem Solving and Structured Programming - Lecture Slides, Slides of Advanced Computer Programming

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Chapter 11

Structured

Types,

Data Abstraction

and Classes

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Chapter 11 Topics

• Meaning of a Structured Data Type

• Declaring and Using a struct Data Type

• C++ union Data Type

• Meaning of an Abstract Data Type

• Declaring and Using a class Data Type

• Using Separate Specification and

Implementation Files

• Invoking class Member Functions in Client

Code

• C++ class Constructors

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Structured Data Type

A structured data type is a type in which each

value is a collection of component items

• The entire collection has a single name
• Each component can be accessed individually
• Used to bundle together related data of various types for convenient access under the same identifier

For example...

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thisAnimal

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.id 2037581 .name “giant panda” .genus “Ailuropoda” .species “melanoluka” .country “China” .age 18 .weight 234. .health Good

struct AnimalType

enum HealthType { Poor, Fair, Good, Excellent }; struct AnimalType // Declares a struct data type { // does not allocate memory long id; string name; string genus; string species; struct members string country; int age; float weight; HealthType health; }; // Declare variables of AnimalType AnimalType thisAnimal; AnimalType anotherAnimal; 7 7

struct type Declaration

SYNTAX

struct TypeName // Does not allocate memory { MemberList };

MemberList SYNTAX

DataType MemberName; DataType MemberName; . . . 8

More about struct type declarations

Scope of a struct

• If the struct type declaration precedes all functions, it will be visible throughout the rest of the file
• If it is placed within a function, only that function can use it

It is common to place struct type declarations in a (.h)

header file and #include that file

It is possible for members of different struct types to have

the same identifiers; also a non-struct variable may have

the same identifier as a structure member

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Accessing struct Members

Dot (period) is the member selection operator

After the struct type declaration, the various members can be

used in your program only when they are preceded by a

struct variable name and a dot

EXAMPLES

thisAnimal.weight

anotherAnimal.country

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Aggregate Operation

An aggregation operation is an operation

on a data structure as a whole, as opposed

to an operation on an individual

component of the data structure

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Aggregate struct Operations

• Operations valid on struct type variables are

 Assignment to another struct variable of the same type

 Pass as an argument (by value or by reference)

 Return as value of a function

• I/O, arithmetic, and comparisons of entire struct

variables are NOT ALLOWED!

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void WriteOut( /* in */ AnimalType thisAnimal) // Prints out values of all members of thisAnimal // Precondition: all members of thisAnimal are assigned // Postcondition:all members have been written out { cout << “ID # “ << thisAnimal.id << thisAnimal.name << endl; cout << thisAnimal.genus << thisAnimal.species << endl; cout << thisAnimal.country << endl; cout << thisAnimal.age << “ years “ << endl; cout << thisAnimal.weight << “ lbs. “ << endl; cout << “General health : “; WriteWord (thisAnimal.health); } 16 Docsity.com

Passing a struct Type by Reference void ChangeAge(/* inout */ AnimalType& thisAnimal) // Adds 1 to age // Precondition: thisAnimal.age is assigned // Postcondition:thisAnimal.age == // thisAnimal.age@entry + 1 { thisAnimal.age++; } 17

Hierarchical Structures

• The type of a struct member can be another

struct type

• This is called nested or hierarchical structures

• Hierarchical structures are very useful when

there is much detailed information in each

record

For example...

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struct MachineRec

Information about each machine in a shop contains:

an idNumber,

a written description,

the purchase date,

the cost,

and a history (including failure rate, number of

days down, and date of last service)

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