C++ Classes

CSE1222: Lecture 19 The Ohio State University 1

List of circles

Represent a list of circles:

vector<double> xlist; // x-coordinates of centers

vector<double> ylist; // y-coordinates of centers

vector<double> rlist; // circle radii


inputCircles.cpp...int main(){ vector<double> xlist; // x-coordinates of circle centers vector<double> ylist; // y-coordinates of circle centers vector<double> rlist; // circle radii double x, y, radius; int n(0);

cout << "Enter number of circles: "; cin >> n;

for (int i = 0; i < n; i++) { cout << "Enter circle " << i << " (x, y, radius): "; cin >> x; xlist.push_back(x); cin >> y; ylist.push_back(y); cin >> radius; rlist.push_back(radius); } ...


Class Circle Create an “object” (C++ class) representing a circle:

class Circle

{

public:

double x;

double y;

double radius;

};


Class Attributes C++ class representing a circle:

class Circle

{

public:

double x;

double y;

double radius;

};

x, y, radius are called the “class attributes” or “data members” of class Circle


Class Attributesclass Circle {

public: double x; double y; double radius; };

To declare a Circle object:Circle c;

To access the Circle attributes:c.xc.yc.radius


Example class Circle

{

public:

double x;

double y;

double radius;

};

... Circle c;

cin >> c.x; cin >> c.y; cin >> c.radius;

cout << "Radius = " << c.radius << endl;


List of circles C++ class representing a circle:

class Circle {

public: double x;

double y;double radius;

};

Declare a vector of class Circle:

vector<Circle> list;


circleClass.cpp...class Circle{public: double x; // x-coordinate of circle center double y; // y-coordinate of circle center double radius; // radius of circle};

int main(){ Circle c; vector<Circle> list; int n(0);...


circleClass.cpp... cout << "Enter number of circles: "; cin >> n;

for (int i = 0; i < n; i++) { cout << "Enter circle " << i << " (x, y, radius): "; cin >> c.x; cin >> c.y; cin >> c.radius; list.push_back(c); }

cout << endl << "Circles:" << endl; for (int i = 0; i < list.size(); i++) { c = list[i]; cout << "Center: (" << c.x << "," << c.y << ")."; cout << " Radius: " << c.radius << endl; }...


circleClass2.cpp...class Circle{public: double x; double y; int radius; // Note: radius is type int, not double};



What’s the error?...class Circle{public: double x; // x-coordinate of circle center double y; // y-coordinate of circle center double radius; // radius of circle}



circleIntersect.cpp...class Circle{public: double x; double y; double radius;};

// protoypesvoid read_circle(const char * prompt, Circle & c);bool intersects(const Circle & c1, const Circle & c2);

int main(){ Circle c1, c2;...


circleIntersect.cpp...// protoypesvoid read_circle(const char * prompt, Circle & c);bool intersects(const Circle & c1, const Circle & c2);

int main(){ Circle c1, c2;

read_circle("Enter first circle (x,y,radius): ", c1); read_circle("Enter second circle (x,y,radius): ", c2);

if (intersects(c1, c2)) { cout << "Circles intersect." << endl; } else { cout << "Circles do not intersect." << endl; };...


read_circle()void read_circle(const char * prompt, Circle & c){ cout << prompt; cin >> c.x; cin >> c.y; cin >> c.radius;}


intersects()bool intersects(const Circle & c1, const Circle & c2){ double diffx = c1.x - c2.x; double diffy = c1.y - c2.y; double dist = sqrt(diffx*diffx + diffy*diffy);

if (dist <= c1.radius + c2.radius) { return(true); } else { return(false); }}


What’s the error?...// protoypesvoid read_circle(const char * prompt, Circle & c);bool intersects(const Circle & c1, const Circle & c2);

class Circle{public: double x; double y; double radius;};

int main(){ Circle c1, c2;...


C++ Classes

Class definition should always be followed by a semicolon:

class Circle{

...

}; // <-Note: semicolon


C++ Classes C++ classes should usually be passed by

reference. (Why?)

Use const if the C++ class is not changed inside the function

Declare C++ classes before function prototypes


Class Circle

class Circle{public: double x; // x-coordinate of circle center double y; // y-coordinate of circle center double radius; // radius of circle};


New Class Circle

class Point{public: double x; // x-coordinate double y; // y-coordinate};

class Circle{public: Point center; // circle center double radius; // circle radius};


circleContains.cpp...int main(){ Circle c; Point p;

cout << "Enter point (x,y): "; cin >> p.x; cin >> p.y;

cout << "Enter circle (x,y,radius): "; cin >> c.center.x; cin >> c.center.y; cin >> c.radius;...


Classes Containing Classes Access the attributes x and y of class center as:

c.center.x c.center.y

For instance:

cout << "Enter circle (x,y,radius): "; cin >> c.center.x; cin >> c.center.y; cin >> c.radius;


circleContains.cpp... double diffx = p.x - c.center.x; double diffy = p.y - c.center.y; double dist = sqrt(diffx*diffx + diffy*diffy);

if (dist <= c.radius) { cout << "Point is inside circle." << endl; } else { cout << "Point is not inside circle." << endl; }

return 0;}


circleContains2.cpp...class Point{public: double x; double y;};

class Circle{public: Point center; double radius;};

void read_point(const char * prompt, Point & p);void read_circle(const char * prompt, Circle & c);double compute_distance(const Point & p1, const Point & p2);...


circleContains2.cpp...int main(){ Circle c; Point p;

read_point("Enter point (x,y): ", p); read_circle("Enter circle (x,y,radius): ", c);

double dist = compute_distance(p, c.center); if (dist <= c.radius) { cout << "Point is inside circle." << endl;} else { cout << "Point is not inside circle." << endl; }

return 0;}...


read_circle() and read_point()void read_circle(const char * prompt, Circle & c){ cout << prompt; cin >> c.center.x; cin >> c.center.y; cin >> c.radius;}

void read_point(const char * prompt, Point & p){ cout << prompt; cin >> p.x; cin >> p.y;}


compute_distance()

double compute_distance(const Point & p1, const Point & p2)

{ double diffx = p1.x - p2.x; double diffy = p1.y - p2.y; double dist = sqrt(diffx*diffx + diffy*diffy);

return(dist);}


compute_distance() Note: Function compute_distance() has no idea that p2

is the center of a circle

...int main(){... double dist = compute_distance(p, c.center);...}

double compute_distance(const Point & p1, const Point & p2){ double diffx = p1.x - p2.x; double diffy = p1.y - p2.y; double dist = sqrt(diffx*diffx + diffy*diffy);

return(dist);}


Comparing Line Segments Write a program to read in two line

segments and report which one is longer

Each line segment has two endpoints Each endpoint has two coordinates


Class LineSegment

class Point{public: double x; double y;};

class LineSegment{public: Point endpoint1; Point endpoint2;};


lineSegment.cpp...void read_point(const char * prompt, Point & p);void read_line_segment (const char * header, LineSegment & seg);double compute_distance (const Point & p1, const Point & p2);

int main(){ LineSegment segA; LineSegment segB;

read_line_segment("Enter first line segment: ", segA); read_line_segment("Enter second line segment: ", segB);...


lineSegment.cpp... double length1 = compute_distance(segA.endpoint1, segA.endpoint2); double length2 = compute_distance(segB.endpoint1, segB.endpoint2);

if (length1 > length2) { cout << "First line segment is longer." << endl; } else if (length2 > length1) { cout << "Second line segment is longer." << endl; } else { cout << "Line segments have equal length." <<

endl; }

return 0;}...


read_point() and read_line_segment()void read_point(const char * prompt, Point & p){ cout << prompt; cin >> p.x; cin >> p.y;}

void read_line_segment (const char * heading, LineSegment & seg){ cout << heading << endl; read_point ("Enter first endpoint (x,y): ", seg.endpoint1); read_point ("Enter second endpoint (x,y): ", seg.endpoint2);}


compute_distance() Note: Function compute_distance() has no idea that

p2 and p2 are line segment endpoints

... double length1 = compute_distance(segA.endpoint1, segA.endpoint2); double length2 = compute_distance(segB.endpoint1, segB.endpoint2);...

double compute_distance(const Point & p1, const Point & p2){ double diffx = p1.x - p2.x; double diffy = p1.y - p2.y; double dist = sqrt(diffx*diffx + diffy*diffy);

return(dist);}


lineSegment2.cpp

class Point{public: double x; double y;};

class LineSegment{public: Point endpoint[2]; // Declare endpoints as an array};


lineSegment2.cpp... double length1 = compute_distance(segA.endpoint[0], segA.endpoint[1]); double length2 = compute_distance(segB.endpoint[0], segB.endpoint[1]);

if (length1 > length2) { cout << "First line segment is longer." << endl; } else if (length2 > length1) { cout << "Second line segment is longer." << endl; } else { cout << "Line segments have equal length." <<

endl; }

return 0;}...


lineSegment2.cpp

void read_point(const char * prompt, Point & p){ cout << prompt; cin >> p.x; cin >> p.y;}

void read_line_segment (const char * heading, LineSegment & seg){ cout << heading << endl; read_point ("Enter first endpoint (x,y): ", seg.endpoint[0]); read_point ("Enter second endpoint (x,y): ", seg.endpoint[1]);}


Class Person

class Person {

public:

int age;

double height;

double weight;

bool gender;

string first_name;

string last_name;

};


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