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Dive into the mechanics of returning structures in C++ with an engaging program that calculates worked hours using start and end times in hh.mm format. This lesson covers the return values from functions, shows how to define and utilize structures, and guides you through writing a program that effectively manages time inputs. Understand the `struct time` definition, argument passing, and the importance of returning structures for more efficient code design. Learn to tackle practical programming challenges by developing robust solutions with this hands-on approach!
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Objectives • Review return value from a function • Returning structures • Program returning a structure
Passing Arguments intans = compute ( z ); int compute ( float zz) { int a; . . . return a; }
Returning Structures struct student { long id; int age; char sex; }; int main ( ) { student s; . . . s = fun (3); . . . } student fun (int n) { student found; . . . return found; }
Why Return a Structure ? struct student { long id; int age; char sex; }; int main ( ) { student s; . . . s = fun (3); . . . } student fun (int n) { student found; . . . return found; }
Program Specifications Write a program that will: Read in a start time and end time in the form hh mm. 2. Calculate and print the total time worked.
Program Code Part 1 #include <iostream> using std::cin; using std::cout; using std::endl; struct time { int hr; int min; }; int main() { time start, end, hoursworked; inti; time calc_hrs (time s, time e);
Program Code Part 2 cout << "enter starting time in the form hh mm "; cin >>start.hr >>start.min; cout << "enter ending time "; cin >>end.hr >>end.min; hoursworked = calc_hrs (start, end); cout << "hours worked = " << hoursworked.hr << " minutes = “ << hoursworked.min; return 0; }
Program Code – Part 3 • /**************function to calculate number of hrs worked******/ • struct time calc_hrs (struct time s, struct time e) • { • struct time hw; • if (s.hr > e.hr) • hw.hr = 24-s.hr +e.hr; /*s = 2300 e = 0115*/ • else • hw.hr = e.hr - s.hr; /*s = 0115 e = 0315*/ • if (e.min < s.min ) /*s = 1215 e = 1509*/ • { • hw.min = 60 - s.min + e.min; • hw.hr--; • } • else • hw.min = e.min - s.min; /*s = 1212 e = 1413*/ • return (hw); • }
Structure Definition struct time { int hr; int min; };
Declarations int main() { time start, end, hoursworked; inti; time calc_hrs (time s, time e); hoursworked end hoursworked.hr end.hr hoursworked.min end.min start start.hr start.min
Inputs cout << "enter starting time in the form hh mm "; cin >>start.hr >>start.min; cout << "enter ending time "; cin >>end.hr >>end.min; hoursworked end hoursworked.hr 11 end.hr hoursworked.min 35 end.min start 9 start.hr 32 start.min
Function Call hoursworked = calc_hrs (start, end);
Print Time Worked cout << "hours worked = " << hoursworked.hr << " minutes = “ << hoursworked.min;
calc_hrs ( ) Function hoursworked = calc_hrs (start, end); time calc_hrs (time s, time e) { struct time hw; s e hw 9 11 s.hr hw.hr e.hr 32 35 hw.min s.min e.min
Calculate Hours Worked if (s.hr > e.hr) hw.hr = 24-s.hr +e.hr; /*s = 2300 e = 0115*/ else hw.hr = e.hr - s.hr; /*s = 0115 e = 0315*/
Calculate Minutes Worked if (e.min < s.min ) /*s = 1215 e = 1509*/ { hw.min = 60 - s.min + e.min; hw.hr--; } else hw.min = e.min - s.min; /*s = 1212 e = 1413*/
Returning the Time Worked return (hw); s e hw 9 11 s.hr hw.hr 2 e.hr 32 35 3 hw.min s.min e.min
Passing & Returning Mechanism hoursworked = calc_hrs (start, end); time calc_hrs (time s, time e) { struct time hw; . . . return hw; } s e hw 9 11 s.hr hw.hr 2 e.hr 32 35 3 hw.min s.min e.min
Why Return a Structure timecalc_hrs (time s, time e) { struct time hw; . . . return hw; }
Summary • Review return value from a function • Returning structures • Program returning a structure
