CSCE 110 PROGRAMMING FUNDAMENTALS WITH C++

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

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

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

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

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: <struct type> <var1> <var2> .. ; Required ; Prof. amr Goneid, AUC

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

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

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

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

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

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

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

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

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

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

16. 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.p2.x,T.p2.y T.p3.x,T.p3.y T.p1.x,T.p1.y Prof. amr Goneid, AUC

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

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

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 constreference if you do not want changes made Prof. amr Goneid, AUC

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

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

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

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

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

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

26. 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 ? ? Prof. amr Goneid, AUC

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

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

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

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 = “3.14159265358979323846264338327950288419716939937510……….”; Prof. amr Goneid, AUC

31. 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 Last NULL head First next cursor Prof. amr Goneid, AUC

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

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