Ch 6-1. Structures. March 30, Prof. Young-Tak Kim

Size: px

Start display at page:

Download "Ch 6-1. Structures. March 30, Prof. Young-Tak Kim"

Cory Lane
5 years ago
Views:

2014-1 Ch 6-1. Structures March 30, 2014 Advanced Networking Technology Lab. (YU-ANTL) Dept. of Information & Comm.

1 Ch 6-1. Structures March 30, 2014 Advanced Networking Technology Lab. (YU-ANTL) Dept. of Information & Comm. Eng, Graduate School, Yeungnam University, KOREA (Tel : ; Fax : ytkim@yu.ac.kr)

2 Outline Structures Structure types Structures as function arguments Initializing structures Passing structure as Parameter Returning structure from called function Structure Array ch

3 Structures 2 nd aggregate data type: struct Recall: aggregate meaning "grouping" Recall array: collection of values of same type Structure: collection of values of different types Treated as a single item, like arrays Major difference: Must first "define" struct Prior to declaring any variables ch

4 Structure Types Define struct globally (typically) No memory is allocated Just a "placeholder" for what our struct will "look like" Definition: typedef struct MyCmplx { // Name of new struct "type" double real; // member names double imagin; double mag; // magnitude } Cmplx; ch

5 Declare Structure Variable With structure type defined, now declare variables of this new type: Cmplx c1, c2; Just like declaring simple types Variable c1 and c2 are now of type Cmplx They contain "member values real, imagin, and mag Each of the struct "parts" ch

6 Accessing Structure Members Dot Operator to access members Cmplx c1; c1.real = 2.0; c1.imagin = 3.0; c1.mag = sqrt(pow(c1.real, 2.0) + pow(c1.imagin, 2.0) ); Called "member variables" The "parts (attribute) of the structure variable Different structs can have same name member variables No conflicts struct Student { int st_id; char name[20]; Date birthdate; }; struct Employ { int emp_id; char name[20]; Date birthdate; }; ch

7 typedef struct MyCmplx { double real; double imagin; double mag; } Cmplx; void printcmplx(cmplx c) { char sign; Structure Example } sign = (c.imagin < 0)? '-' : '+'; cout << setw(8) << c.real <<" " << sign << " j" << fabs(c.imagin) ; cout << " (magnitude " << c.mag << ")" << endl; Cmplx cmplxadd(cmplx c1, Cmplx c2) { Cmplx res; res.real = c1.real + c2.real; res.imagin = c1.imagin + c2.imagin; res.mag = sqrt(res.real*res.real + res.imagin*res.imagin); return res; } ch

8 Cmplx cmplxsub(cmplx c1, Cmplx c2) { Cmplx res; res.real = c1.real - c2.real; res.imagin = c1.imagin - c2.imagin; res.mag = sqrt(res.real*res.real + res.imagin*res.imagin); return res; } Cmplx cmplxmultiply(cmplx c1, Cmplx c2) { Cmplx res; res.real = (c1.real * c2.real) - (c1.imagin * c2.imagin); res.imagin = (c1.real * c2.imagin) + (c1.imagin * c2.real); res.mag = sqrt(res.real*res.real + res.imagin*res.imagin); return res; } Cmplx cmplxdivide(cmplx c1, Cmplx c2) { Cmplx res; double denom; denom = c2.real*c2.real + c2.imagin*c2.imagin; res.real = ((c1.real * c2.real) + (c1.imagin * c2.imagin)) / denom; res.imagin = ((c2.real * c1.imagin) - (c1.real * c2.imagin)) / denom; res.mag = sqrt(res.real*res.real + res.imagin*res.imagin); return res; } ch

9 1. int main() 2. { 3. Cmplx cmplxs[7]; 4. cout << "Input two complex numbers : c1.real, c1.imagin, 5. cout << c2.real, c2.imagin"<<endl; 6. cout << "c1.real : "; 7. cin >> cmplxs[0].real; 8. cout << "c1.imagin : "; 9. cin >> cmplxs[0].imagin; 10. cmplxs[0].mag = sqrt((cmplxs[0].real*cmplxs[0].real) (cmplxs[0].imagin * cmplxs[0].imagin)); 12. cout << "c2.real : "; 13. cin >> cmplxs[1].real; 14. cout << "c2.imagin : "; 15. cin >> cmplxs[1].imagin; 16. cmplxs[1].mag = sqrt((cmplxs[1].real*cmplxs[1].real) (cmplxs[1].imagin * cmplxs[1].imagin)); ch

10 18. cmplxs[2] = cmplxadd(cmplxs[0], cmplxs[1]); 19. cmplxs[3] = cmplxsub(cmplxs[0], cmplxs[1]); 20. cmplxs[4] = cmplxmultiply(cmplxs[0], cmplxs[1]); 21. cmplxs[5] = cmplxdivide(cmplxs[0], cmplxs[1]); 22. cmplxs[6] = cmplxs[0]; 23. for (int i=0; i<7; i++) { 24. cout << "cmplxs[" << i << "]: "; 25. printcmplx(cmplxs[i]); 26. } 27. return 0; 28.} ch

11 Structure Pitfall Semicolon after structure definition ; MUST exist: struct WeatherData { double temperature; double windvelocity; }; REQUIRED semicolon! Required since you "can" declare structure variables in this location ch

12 Structure Assignments Given structure named Cmplx Declare two structure variables: Cmplx c1, c2; Both are variables of "struct type Cmplx" Simple assignments are legal: c2 = c1; Simply copies each member variable from c1 into member variables of c2 ch

13 Structures as Function Arguments Passed like any simple data type Pass-by-value Pass-by-reference Or combination Can also be returned by function Return-type is structure type Return statement in function definition sends structure variable back to caller ch

14 Initializing Structures Can initialize at declaration Example: struct Planet { char name[10]; double relativemass; double distance; }; struct Planet earth = { Earth, 1.0, 150}; Declaration provides initial data to all three member variables ch

15 Array of Structure Struct data elements can be organized in array Example) struct Planet solarsystem[solar_planets] = { {"Mercury", , 57.9}, {"Venus", 0.815, 108}, {"Earth",1.0, 150}, {"Mars", 0.107, 228}, {"Jupiter", 318, 778}, {"Saturn", 95.1, 1430}, {"Uranus", 14.5, 2870}, {"Neptune", 17.2, 4500}, {"Pluto", 0.11, 5900} }; ch

16 Handling attributes of each element of struct array void printplanets(struct Planet solarplanets[], int num_planet) 1. { 2. cout.setf(ios::fixed); 3. cout.setf(ios::showpoint); 4. for (int i=0; i<num_planet; i++) { 5. cout << setw(2) << i; 6. cout << " Name: "; 7. cout << setiosflags(ios::left) <<setw(8) << solarplanets[i].name; 8. cout << resetiosflags(ios::left); 9. cout << " Rel Mass: "; 10. cout << setw(7) << setprecision(3) <<solarplanets[i].relativemass; 11. cout << " Dist from Sun: "; 12. cout << setw(6) << setprecision(1) << solarplanets[i].distance ; 13. cout << endl; 14. } // end for 15.} ch

17 Sorting Array of Structure Sorting elements in array of structure (1) void sortplanetsbyrelmass(struct Planet solarplanets[], int num_planet) 1. { 2. struct Planet temp; 3. int i, j, m; 4. double min_relmass; 5. for (i=0; i<num_planet-1; i++) { 6. m = i; 7. min_relmass = solarplanets[i].relativemass; 8. for (j=i+1; j<num_planet; j++) { 9. if (min_relmass > solarplanets[j].relativemass) { 10. m = j; 11. min_relmass = solarplanets[j].relativemass; 12. } 13. } // end inner for 14. if (m!= i) { // if new minimum found, swap 15. temp = solarplanets[i]; 16. solarplanets[i] = solarplanets[m]; 17. solarplanets[m] = temp; 18. } 19. } // end outer for 20. } ch

18 Sorting elements in array of structure (2) void sortplanetsbyname(struct Planet solarplanets[], int num_planet) { 1. struct Planet temp; 2. int i, j, m; 3. char min_name[10] = {0}; 4. for (i=0; i<num_planet-1; i++) { 5. m = i; 6. strcpy(min_name, solarplanets[i].name); 7. for (j=i+1; j<num_planet; j++) { 8. if (strcmp(min_name, solarplanets[j].name) > 0) { 9. m = j; 10. strcpy(min_name, solarplanets[j].name); 11. } 12. } // end inner for 13. if (m!= i) { // if new minimum found, swap 14. temp = solarplanets[i]; 15. solarplanets[i] = solarplanets[m]; 16. solarplanets[m] = temp; 17. } 18. } // end outer for 19.} ch

19 1. int main() { 2. struct Planet solarsystem[solar_planets] = 3. {{"Mercury", , 57.9}, {"Venus", 0.815, 108}, {"Earth",1.0, 150}, 4. {"Mars", 0.107, 228}, {"Jupiter", 318, 778}, {"Saturn", 95.1, 1430}, 5. {"Uranus", 14.5, 2870}, {"Neptune", 17.2, 4500}, {"Pluto", 0.11, 5900} }; 6. cout << "Initial state" << endl; 7. printplanets(solarsystem, SOLAR_PLANETS); 8. sortplanetsbyrelmass(solarsystem, SOLAR_PLANETS); 9. cout << " nafter sorting by relative mass:" << endl; 10. printplanets(solarsystem, SOLAR_PLANETS); 11. sortplanetsbydist(solarsystem, SOLAR_PLANETS); 12. cout << " nafter sorting by distance from sun:" << endl; 13. printplanets(solarsystem, SOLAR_PLANETS); 14. sortplanetsbyname(solarsystem, SOLAR_PLANETS); 15. cout << " nafter sorting by name using strcmp and strcpy:" << endl; 16. printplanets(solarsystem, SOLAR_PLANETS); 17. cout << " n n"; return 0; 20.} ch

20 result of execution ch

21 Homework Calendar system with structure for date 1) Design a structure for date that contains day, month, year, yearday and month_name. struct Date { int day; int month; int year; int yearday; char month_name[10]; }; yearday means the sequence number of the day from the January 1 of the year. 2) Input a date from console terminal in format of three integers for day, month, and year. For example, means April 12, Initialize the month_name of the input date, determine whether the year is leap year or not. And, calculate the yearday. In this date handling function, use dot. operator. ch

22 3) Write a function that increment the given date by the specified number of days. The prototype is void incrementdate(date& dptr, int days), which is using Call-by-Reference in parameter passing. Input an integer number, and increase the date initialized in step 2) (by the input integer data). The month and year must be calculated correctly at the date increment. 4) Write a function int datecompare(const Date& d1, const Date& d2) that compares two dates, and returns the difference of the two dates yearday. The function receives two arguments of Date structure, passed by call-by-pointer. The return type is integer. Using the first date (input from console) and the increased date, calculate the difference of the two dates using the datecompare() function. ch

Ch 6. Structures and Classes

2013-2 Ch 6. Structures and Classes September 1, 2013 Advanced Networking Technology Lab. (YU-ANTL) Dept. of Information & Comm. Eng, Graduate School, Yeungnam University, KOREA (Tel : +82-53-810-2497;