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Nov 18, 2022 •258 likes •600 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

  1. CSCE 110 PROGRAMMING FUNDAMENTALS WITH C++ Prof. Amr Goneid AUC Part 11. The Struct Data Type Prof. amr Goneid, AUC 1

  2. The Struct Data Type Prof. amr Goneid, AUC 2

  3. 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 Prof. amr Goneid, AUC 3

  4. 1. What are structs?  Structs are linear Data Structures.  Unlike the array, components ( members ) can be of different types . string Member 1 int Member 2 One struct longint char Member n int Prof. amr Goneid, AUC 4

  5. 2. Definition & Declaration (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: Required ; <struct type> <var1> <var2> .. ; Prof. amr Goneid, AUC 5

  6. Example // Definition of struct employee struct employee { string id; string name; char gender; int numDepend; money rate; money totWages; }; employee engineer , assistant; Prof. amr Goneid, AUC 6

  7. 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 on struct members Prof. amr Goneid, AUC 7

  8. 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; Prof. amr Goneid, AUC 8

  9. 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 or by reference  Return a struct as a function type Prof. amr Goneid, AUC 9

  10. 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 Prof. amr Goneid, AUC 10

  11. 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 Prof. amr Goneid, AUC 11

  12. 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 Prof. amr Goneid, AUC 12

  13. 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); Prof. amr Goneid, AUC 13

  14. 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]; Prof. amr Goneid, AUC 14

  15. 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; Prof. amr Goneid, AUC 15

  16. Structs with Struct Members struct point{ p.x,p.y double x, y; }; point P; struct line{ L.p1.x,L.p1.y L.p2.x,L.p2.y point p1, p2; }; line L; struct triangle{ T.p2.x,T.p2.y T.p3.x,T.p3.y point p1, p2, p3; }; triangle T; T.p1.x,T.p1.y Prof. amr Goneid, AUC 16

  17. 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; } Prof. amr Goneid, AUC 17

  18. 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]; Prof. amr Goneid, AUC 18

  19. 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 Prof. amr Goneid, AUC 19

  20. Example(1): Grading Program // FILE: StudentStat.h struct studentStat { string name; int scores[3]; float average; char grade; }; Prof. amr Goneid, AUC 20

  21. 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 << ": " Prof. amr Goneid, AUC 21

  22. 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; } Prof. amr Goneid, AUC 22

  23. 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 # : "; Prof. amr Goneid, AUC 23

  24. 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; } Prof. amr Goneid, AUC 24

  25. 7. Pointers to Structs struct electric { string current; int volts; }; electric *p, *q; //p and q are pointers to a struct of type electric Prof. amr Goneid, AUC 25

  26. Pointers to Structs p = new electric;  Allocates storage for struct of type electric and places address into pointer p current volts p ? ?  Use operator ( . ) to access struct members. Prof. amr Goneid, AUC 26

  27. Assignments *p.current = “AC”; *p.volts = 220; current volts p AC 220  Statements above can also be written as p ->current = “AC”; p ->volts = 220; Prof. amr Goneid, AUC 27

  28. Struct Member Access via Pointers  Form: p -> <member>  Example: p -> volts  Example: cout << p->current << p-volts << endl;  Output AC220 Prof. amr Goneid, AUC 28

  29. 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; q ->current q ->volts q AC 220 Prof. amr Goneid, AUC 29

  30. 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……….”; Prof. amr Goneid, AUC 30

  31. The Simple Linked List  We can build a sequence of nodes linked by pointers: . 3 1 Last NULL head First next cursor  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. Prof. amr Goneid, AUC 31

  32. 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 Prof. amr Goneid, AUC 32

  33. 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; } Prof. amr Goneid, AUC 33

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