WITH C++ Prof. Amr Goneid AUC Part 11. The Struct Data Type Prof. - - PowerPoint PPT Presentation

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WITH C++ Prof. Amr Goneid AUC Part 11. The Struct Data Type Prof. - - PowerPoint PPT Presentation

Nov 18, 2022 258 likes •606 views

CSCE 110 PROGRAMMING FUNDAMENTALS WITH C++ Prof. Amr Goneid AUC Part 11. The Struct Data Type Prof. amr Goneid, AUC 1 The Struct Data Type Prof. amr Goneid, AUC 2 The Struct Data Type What are Structs ? Definition & Declaration

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  • Prof. amr Goneid, AUC

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CSCE 110 PROGRAMMING FUNDAMENTALS

WITH C++

  • Prof. Amr Goneid

AUC Part 11. The Struct Data Type

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  • Prof. amr Goneid, AUC

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The Struct Data Type

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The Struct Data Type

 What are Structs ?  Definition & Declaration  Accessing Members of a Struct  Initializing a Struct Variable  Compound Structs  Structs as Operands & Arguments  Pointers to Structs

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  • 1. What are structs?

 Structs are linear Data Structures.  Unlike the array, components

(members) can be of different types.

string int longint int Member 1 Member 2 Member n One struct char

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(a) Define a struct type: struct <struct type> { <type 1> <member 1>; <type 2> <member 2>; …… <type n> <member n>; }; (b) Declare variables of that type: <struct type> <var1> <var2> .. ;

  • 2. Definition & Declaration

Required ;

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Example

// Definition of struct employee struct employee { string id; string name; char gender; int numDepend; money rate; money totWages; }; employee engineer , assistant;

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  • 3. Accessing Members of a

struct

 Members are accessed using the

member access operator, a period (.)

 For struct variable s and member

variable m, to access m you would use: s.m

 Can use C++ operators and operations

  • n struct members
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Accessing Members of a struct

engineer.id = “1234”; engineer.name = “Heba Ahmed”; engineer.gender = ‘F’; engineer.numDepend = 0; engineer.rate = 6.00; engineer.totWages += engineer.rate * 40.0;

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What you can do with a whole struct

 Assign a struct to another struct with

exactly the same structure (copy)

 Pass a struct to a function by value

  • r by reference

 Return a struct as a function type

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BUT you cannot

 Input or output a whole struct  Do arithmetic with whole structs  Compare two whole structs

The above operations can only be done on individual members of structs

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  • Prof. amr Goneid, AUC

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  • 4. Initializing a Struct Variable

 Members can be initialized at the time a

structure variable is created using a constructor

 A constructor is a special function that

can be a member of a structure

 It is normally written inside the struct

declaration

 Its purpose is to initialize the structure’s

data members

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Initializing using a Constructor

 Unlike most functions, a constructor is not

called; instead, it is automatically invoked when a structure variable is created

 The constructor name must be the same

as the structure Type name

 The constructor must have no return type

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Initializing using a Constructor

Example: struct Dimensions { int length, width, height; // Constructor Dimensions(int L, int W, int H) {length = L; width = W; height = H;} }; Usage: Dimensions box(12, 6, 3);

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  • 5. Compound structs:

Structs with Array Members

// Arrays can be fields of structs, e.g. struct studentRecord { string name; string id; float grade [10]; float GPA; }; studentRecord student; student.grade[3] = 3.6; cin >> student.name; for( i = 0; i < 10; i++) cin >> student.grade[i];

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Structs with Struct Members

// A member of a struct may itself be a struct,e.g. struct nameType { cin >> person.address; string first; cin >> person.phone; string middle; cin >> person.name.first; string last; cin >> person.name.last; }; struct personInfo { nameType name; string address; string phone; }; personInfo person;

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Structs with Struct Members

struct point{ double x, y; }; point P; struct line{ point p1, p2; }; line L; struct triangle{ point p1, p2, p3; }; triangle T;

p.x,p.y L.p1.x,L.p1.y L.p2.x,L.p2.y T.p1.x,T.p1.y T.p2.x,T.p2.y T.p3.x,T.p3.y

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Arrays of Structs

// A struct may be an element of an // array,e.g. personInfo staff [100]; cout << staff [i].address; cout << staff [i].name.first; for( i = 0; i < N; i++) { cout << staff [i].phone; cout << staff [i].name.family; }

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  • 6. Structs as Operands and Arguments

 Arithmetic and other operations can be

done struct members

 Process entire struct using programmer

defined functions

 Often better to pass an entire structure

rather than individual elements

 struct copies:

person = staff [6];

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Passing struct as an Argument

 Grading program example  Keep track of students grades  Prior to our learning structs we needed

to store each item into a single variable

 Group all related student items together  Pass struct by const reference if you do

not want changes made

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Example(1): Grading Program

// FILE: StudentStat.h struct studentStat { string name; int scores[3]; float average; char grade; };

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PrintStats.cpp

// File: printStats.cpp // Prints the exam statistics // Pre: The members of the struct variable // student are assigned values. // Post: Each member of student is displayed. void printStats(const studentStat student) { cout << "Exam scores for " << student. name << ": "

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PrintStats.cpp

cout << student.scores[0] << ' ' << student.scores[1]<< ' ' << student.scores[2] << endl; cout << "Average score: " << student.average << endl; cout << "Letter grade : " << student.grade << endl; }

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Example(2): ReadEmp.cpp

// File: ReadEmp.cpp // Reads one employee record into oneemployee #include <string> #include <iostream> // Pre: None // Post: Data are read into struct oneEmployee void readEmployee(employee& oneEmployee) { cout << "Enter a name terminated by # : ";

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ReadEmp.cpp

getline(cin, oneEmployee.name, '#'); cout << "Enter an id number: "; cin >> oneEmployee.id; cout << "Enter gender (F or M): "; cin >> oneEmployee.gender; cout << "Enter number of dependents: "; cin >> oneEmployee.numDepend; cout << "Enter hourly rate: "; cin >> oneEmployee.rate; }

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  • 7. Pointers to Structs

struct electric { string current; int volts; }; electric *p, *q;

//p and q are pointers to a struct of type electric

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Pointers to Structs

p = new electric;

 Allocates storage for struct of type electric

and places address into pointer p

 Use operator ( . ) to access struct members. ? current volts p ?

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Assignments

*p.current = “AC”; *p.volts = 220;

 Statements above can also be written as p ->current = “AC”; p ->volts = 220; AC current volts p 220

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Struct Member Access via Pointers

 Form:

p -> <member>

 Example:

p -> volts

 Example:

cout << p->current << p-volts << endl;

 Output

AC220

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Copy Dynamic Structs

q = new electric;

 Allocates storage for struct of type electric and places

address into pointer q

 Copy contents of p struct to q struct

*q = *p; AC q ->current q ->volts q 220

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The Linked List Structure

 Structs and pointers can be used to arrange

dynamically allocated structures into a new structure called a linked list

 Example: Consider a very long number

represented as a string, e.g. π string Long_pi = “3.1415926535897932384626433832795028 8419716939937510……….”;

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The Simple Linked List

 We can build a sequence of nodes linked by

pointers:

 First node pointed to by head contains the first digit

‘3’and a next pointer to next node containing ‘.’ and so on.

 Last node’s next is NULL.  A cursor points to the current node. It can advance

in one way only to next node, e.g. to traverse whole list. 3 1

head NULL

cursor

. next First Last

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The Node Structure

struct node // specify node structure { char d; // digit or ‘.’ node *next; // pointer to next node }; node *head, *cursor , *p; // pointers to nodes d

next

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Code segment

// Create first node p = new node; p->d = Long_pi[0]; p-> next = NULL; head = cursor = p; //Create rest of nodes for (i = 1; i < Long_pi.length(); i++){ p = new node; p->d = Long_pi[i]; p->next = NULL; cursor->next = p; cursor = cursor->next; }