EECE.2160 ECE Application Programming Instructor: Dr. Michael Geiger Fall 2017 Lecture 27: Nested structures

ECE Application Programming: Lecture 27 Lecture outline Announcements/reminders Program 6 graded; regrades due 11/29 Program 7 posted; due 11/20 Programs submitted 11/21-11/26 “1 day late” Late penalties begin increasing again on 11/27 Today’s class Structures and functions example Nested structures Start PE4 (Structures) 2/17/2019 ECE Application Programming: Lecture 27

ECE Application Programming: Lecture 27 Review: Structures User-defined types; example: typedef struct { char first[50]; char middle; char last[50]; unsigned int ID; double GPA; } StudentInfo; Can define variables of that type Scalar: StudentInfo student1; Array: StudentInfo classList[10]; Pointer: StudentInfo *sPtr = &student1; Access members using Dot operator: student1.middle = ‘J’; Arrow (if pointers): sPtr->GPA = 3.5; Typically passed to functions by address 2/17/2019 ECE Application Programming: Lecture 27

Review: Structures and functions Can pass structures to functions int f(StudentInfo s); Structures consume significant memory Usually much more efficient to simply pass pointer int g(StudentInfo *p); Access structure through pointer: -> operator Handles dereferencing and field access Example: p->GPA = 3.0; 2/17/2019 ECE Application Programming: Lecture 27

Example: Structures and functions Write the following functions that use the StudentInfo structure Given a pointer to a single StudentInfo variable, print all of the student info to the screen using the following format: Michael J. Geiger ID #12345678 GPA: 1.23 Given an array of StudentInfo variables and the size of the array, compute and return the average GPA of all students in the list Prompt the user to enter 3 lines of input (using the format below), read the appropriate values into StudentInfo elements, and return a value of type StudentInfo Format (user input underlined) Enter name: Michael J. Geiger Enter ID #: 12345678 Enter GPA: 1.23 2/17/2019 ECE Application Programming: Lecture 27

ECE Application Programming: Lecture 27 Example solution void printStudent(StudentInfo *s) { printf(“%s %c. %s\n”, s->first, s->middle, s->last); printf(“ID #%u\n”, s->ID); printf(“GPA %.2lf\n”, s->GPA); } 2/17/2019 ECE Application Programming: Lecture 27

Example solution (cont.) double avgGPA(StudentInfo list[], int n) { int i; int sum = 0; for (i = 0; i < n; i++) sum += list[i].GPA; return sum / n; } 2/17/2019 ECE Application Programming: Lecture 27

Example solution (cont.) StudentInfo readStudent() { StudentInfo s; printf(“Enter name: ”); scanf(“%s %c. %s”, s.first, &s.middle, s.last); printf(“Enter ID #: ”); scanf(“%u”, &s.ID); printf(“Enter GPA: ”); scanf(“%lf”, &s.GPA); return s; } 2/17/2019 ECE Application Programming: Lecture 27

ECE Application Programming: Lecture 27 Nested structures Structures can contain other structures: typedef struct { char first[50]; // First name char middle; // Middle initial char last[50]; // Last name } Name; Name sname; // Student name unsigned int ID; // ID # double GPA; // Grade point } SINew; Will need multiple dot operators to access field within nested structure Given SINew s1; s1.sname  Name structure within s1 s1.sname.middle  middle initial of name within s1 2/17/2019 ECE Application Programming: Lecture 27

ECE Application Programming: Lecture 27 PE4 (Structures) Given header files, main program Complete specified functions For the Name structure void printName(Name *n): Print the name pointed to by n, using format <first> <middle>. <last> void readName(Name *n): Prompt for and read a first, middle, and last name, and store them in the structure pointed to by n SINew functions on next slide 2/17/2019 ECE Application Programming: Lecture 27

Today’s exercise (continued) Given header files, main program Complete specified functions Name functions on previous slide For the SINew structure void printStudent(SINew *s): Print information about the student pointed to by s void readStudent(SINew *s): Prompt for and read information into the student pointed to by s void printList(SINew list[], int n): Print the contents of an array list that contains n StudentInfo structures int findByLName(SINew list[], int n, char lname[]): Search for the student with last name lname in the array list. Return the index of the structure containing that last name, or -1 if not found int findByID(SINew list[], int n, unsigned int sID): Search for the student with ID # sID in the array list. Return the index of the structure containing that last name, or -1 if not found 2/17/2019 ECE Application Programming: Lecture 27

ECE Application Programming: Lecture 27 Next time Finish PE4 File I/O Reminders: Program 6 graded; regrades due 11/29 Program 7 posted; due 11/20 Programs submitted 11/21-11/26 “1 day late” Late penalties begin increasing again on 11/27 2/17/2019 ECE Application Programming: Lecture 27