C++ Tutorial/Structure/structure

Assign one structure to another structure

<source lang="cpp">#include <iostream> using std::cout; using std::endl; struct Box {

 double length;
 double width;
 double height;

}; int main() {

 Box firstBox = { 80.0, 50.0, 40.0 };
 cout << firstBox.length
      << firstBox.width
      << firstBox.height
      << endl;
      
 Box secondBox = firstBox;   
 secondBox.length *= 1.1;
 secondBox.width *= 1.1;
 secondBox.height *= 1.1;
 cout << secondBox.length 
      << secondBox.width
      << secondBox.height
      << endl;
 
 return 0;

}</source>

805040
885544

const structure parameter

<source lang="cpp">#include <iostream.h> struct Time {

      int hh,mm,ss;

}; void Disp1(struct Time t); void Disp2(const Time & t); int main() {

      Time t1,t2,*p;
      
      t1.hh=10;
      t1.mm=30;
      t1.ss=0;
      t2=t1;  
      t2.hh++;                        
      p = &t2;
   
   cout << "The t2 time is " << p->hh  << ":" << t2.mm << ":"<< t1.ss << endl;
      Disp1(t2);
      Disp2(t2);
      
      return 0;

} void Disp1(struct Time t) {

      cout << "The time is " << t.hh <<":" << t.mm << ":"<< t.ss << endl;

} void Disp2(const Time & t) {

      cout << "The time is " << t.hh <<":" << t.mm << ":"<< t.ss << endl;

}</source>

The t2 time is 11:30:0
The time is 11:30:0
The time is 11:30:0

Define structure to record time

<source lang="cpp">#include <iostream.h> struct Time {

              int hh,mm,ss;

}; int main() {

  Time t1,t2,*p;
  t1.hh=10;
  t1.mm=30;
  t1.ss=0;  //10:30:0
  t2=t1;
  t2.hh++;                             //11:30:0
  p = &t2;
  cout << "The t2 time is " << p->hh  << ":" << t2.mm << ":"<< t1.ss << endl;
  return 0;

}</source>

The t2 time is 11:30:0

structure composition

<source lang="cpp">#include <iostream> using std::cout; using std::endl;

1. include <iostream>

struct Name {

 char firstname[80];
 char surname[80];
 
 void show();        

}; struct Date {

 int day;
 int month;
 int year;
 void show();        

}; struct Phone {

 int areacode;
 int number;
 void show();        

}; struct Person {

 Name name;
 Date birthdate;
 Phone number;
 void show();
 int age(Date& date);

}; void Name::show() {

   std::cout << firstname << " " << surname << std::endl;

} void Date::show() {

   std::cout << month << "/" << day << "/" << year << std::endl;

} void Phone::show() {

   std::cout << areacode << " " << number << std::endl;

} void Person::show() {

   std::cout << std::endl;
   name.show();
   std::cout << "Brithday: ";
   birthdate.show();
   std::cout << "phone: ";
   number.show(); 

} int Person::age(Date& date) {

   if(date.year <= birthdate.year)
     return 0;
   int years = date.year - birthdate.year;
   
   if((date.month>birthdate.month) || (date.month == birthdate.month && date.day>= birthdate.day))
      return years;
   else
      return --years;

}

int main() {

 Person her = {{ "L", "G" },      // Initializes Name member
               {1, 4, 1976 },     // Initializes Date member
               {999,5551234}     // Initializes Phone member
              };
 Person actress;
 actress = her;
 her.show();
 Date today = { 4, 4, 2007 };
 cout << endl << "Today is ";
 today.show();
 cout <<  endl; 
 cout << "Today " << actress.name.firstname << " is " 
      << actress.age(today) << " years old."
      << endl;
 return 0;

}</source>

L G
Brithday: 4/1/1976
phone: 999 5551234
Today is 4/4/2007
Today L is 31 years old.

Use cin to read data for a structure

<source lang="cpp">#include<iostream.h>

1. include<stdio.h>
2. include<stdlib.h>
3. include<string.h>

int main() {

      struct student
      {
              int num;
          char name[20];
          float score;
      };
      struct student stu[4];
      struct student *p;
      int i,temp;
      float max;
      for(i=0;i<=4;i++)
              cin>>stu[i].num>>stu[i].name>>stu[i].score;
      for(max=stu[0].score,i=1;i<4;i++){
              if(stu[i].score>max);
              {
                      max=stu[i].score;temp=i;
              }
   }
      p=stu+temp;
      cout<<"maxmum score:";
      cout<<"NO.:"<<p->num<<"NAME:"<<p->name<<"SCORE:"<<p->score<<"\n";

}</source>

maxmum score:NO.:^CTerminate batch job (Y/N)? n

Use memcpy to duplicate structures

<source lang="cpp">#include <memory>

1. include <iostream>

using namespace std; struct mystruct {

      int i;
      int x;
      int y;

};

int main() {

 mystruct source,destination;
 source.i = 1;
 source.x = 2;
 source.y = 3;
 memcpy(&destination,&source,sizeof(source));
 cout << destination.i << endl;
 cout << destination.x << endl;
 cout << destination.y << endl;
 return 0;

}</source>

1
2
3

Use the keyword struct to illustrate a primitive form of class

<source lang="cpp">#include <iostream>

1. include <math.h>

using namespace std; struct math_operations {

double data_value;
 
void set_value(double ang) {
    data_value=ang;
}
double get_square(void) {
    double answer;
    answer=data_value*data_value;                          
    return (answer);
}
double get_square_root(void) {
    double answer;
    answer=sqrt(data_value);
    return (answer);
}

} math; int main( ) {

math.set_value(35.63);
cout << "The square of the number is: "
     << math.get_square( ) << endl;
cout << "The square root of the number is: "
     << math.get_square_root( ) << endl;
return (0);

}</source>

Using pointers to structure objects: delete the point

<source lang="cpp">#include <iostream> using std::cout; using std::endl; struct Box {

 double length;
 double width;
 double height;
 double volume();

}; double Box::volume() {

 return length * width * height;

}

int main() {

 Box aBox = { 1, 2, 3 };
 Box* pBox = &aBox;

 Box* pBox2 = new Box;
 pBox2->height = pBox->height+5.0;
 pBox2->length = pBox->length+3.0;
 pBox2->width = pBox->width+2.0;
 cout << "Volume of Box in the free store is " << pBox2->volume() << endl;
 delete pBox;
 delete pBox2;
 return 0;

}</source>

Volume of Box in the free store is 128