After going through previous post, we know what exactly are complex numbers and how we can use them to simulate points in a cartesian plane. Now, we will have an insight as to how to use the complex class from STL in C++.

**To use the complex class from STL we use #include <complex>**

**Defining Point Class**

We can define our point class by typedef complex<double> point; at the start of the program. The X and Y coordinates of the point are the real and imaginary part of the complex number respectively. To access our X- and Y-coordinates, we can macro the real() and imag() functions by using #define as follows:

# include <complex> typedef complex<double> point; # define x real() # define y imag()

**Drawback:** Since x and y have been used as macros, these can’t be used as variables. However, this drawback doesn’t stand in front of the many advantages this serves.

`// CPP program to illustrate ` `// the definition of point class` `#include <iostream>` `#include <complex>` ` ` `using` `namespace` `std;` ` ` `typedef` `complex<` `double` `> point;` ` ` `// X-coordinate is equivalent to the real part` `// Y-coordinate is equivalent to the imaginary part` `#define x real()` `#define y imag()` ` ` `int` `main()` `{` ` ` `point P(2.0, 3.0);` ` ` `cout << ` `"The X-coordinate of point P is: "` `<< P.x << endl;` ` ` `cout << ` `"The Y-coordinate of point P is: "` `<< P.y << endl;` ` ` ` ` `return` `0;` `}` |

Output:

The X-coordinate of point P is: 2 The Y-coordinate of point P is: 3

**Implementation of attributes with respect to P single point P in plane:**

**The X coordinate of P:**P.x**The Y coordinate of P:**P.y**The distance of P from origin (0, 0):**abs(P)**The angle made by OP from the X-Axis where O is the origin:**arg(z)**Rotation of P about origin:**P * polar(r, θ)`// CPP program to illustrate`

`// the implementation of single point attributes`

`#include <iostream>`

`#include <complex>`

`using`

`namespace`

`std;`

`typedef`

`complex<`

`double`

`> point;`

`#define x real()`

`#define y imag()`

`// The constant PI for providing angles in radians`

`#define PI 3.1415926535897932384626`

`// Function used to display X and Y coordiantes of a point`

`void`

`displayPoint(point P)`

`{`

`cout <<`

`"("`

`<< P.x <<`

`", "`

`<< P.y <<`

`")"`

`<< endl;`

`}`

`int`

`main()`

`{`

`point P(4.0, 3.0);`

`// X-Coordinate and Y-coordinate`

`cout <<`

`"The X-coordinate of point P is: "`

`<< P.x << endl;`

`cout <<`

`"The Y-coordinate of point P is: "`

`<< P.y << endl;`

`// Distances of P from origin`

`cout <<`

`"The distance of point P from orgin is: "`

`<<`

`abs`

`(P) <<endl;`

`cout <<`

`"The squared distance of point P from orgin is: "`

`<< norm(P) <<endl;`

`// Tangent Angle made by OP with the X-Axis`

`cout <<`

`"The angle made by OP with the X-Axis is: "`

`<< arg(P) <<`

`" radians"`

`<< endl;`

`cout <<`

`"The angle made by OP with the X-Axis is: "`

`<< arg(P)*(180/PI) <<`

`" degrees"`

`<< endl;`

`// Rotation of P about origin`

`// The angle of rotation = 90 degrees`

`point P_rotated = P * polar(1.0, PI/2);`

`cout<<`

`"The point P on rotating 90 degrees anti-clockwise becomes: P_rotated"`

`;`

`displayPoint(P_rotated);`

`return`

`0;`

`}`

Output:

The X-coordinate of point P is: 4 The Y-coordinate of point P is: 3 The distance of point P from orgin is: 5 The squared distance of point P from orgin is: 25 The angle made by OP with the X-Axis is: 0.643501 radians The angle made by OP with the X-Axis is: 36.8699 degrees The point P on rotating 90 degrees anti-clockwise becomes: P_rotated(-3, 4)

Let us consider points P (a, b) and Q (c, d) on the Euclidean Plane.

**Implementation of attributes with respect to P and Q.****Vector Addition:**P + Q**Vector Subtraction:**P – Q**Euclidean Distance:**abs(P – Q)**Slope of line PQ:**tan(arg(Q – P))point A = conj(P) * Q

**Dot Product:**A.x**Magnitude of Cross Product:**abs(A.y)

`// CPP program to illustrate ` `// the implementation of two point attributes` `#include <iostream>` `#include <complex>` ` ` `using` `namespace` `std;` ` ` `typedef` `complex<` `double` `> point;` `#define x real()` `#define y imag()` ` ` `// Constant PI for providing angles in radians` `#define PI 3.1415926535897932384626` ` ` `// Function used to display X and Y coordiantes of a point` `void` `displayPoint(point P)` `{` ` ` `cout << ` `"("` `<< P.x << ` `", "` `<< P.y << ` `")"` `<< endl;` `}` ` ` `int` `main()` `{` ` ` `point P(2.0, 3.0);` ` ` `point Q(3.0, 4.0);` ` ` ` ` `// Addition and Subtraction` ` ` `cout << ` `"Addition of P and Q is: P+Q"` `; displayPoint(P+Q);` ` ` `cout << ` `"Subtraction of P and Q is: P-Q"` `; displayPoint(P-Q);` ` ` ` ` `// Distances between points P and Q` ` ` `cout << ` `"The distance between point P ans Q is: "` `<< ` `abs` `(P-Q) <<endl;` ` ` `cout << ` `"The squared distance between point P ans Q is: "` `<< norm(P-Q) <<endl;` ` ` ` ` `// Slope of line PQ` ` ` `cout << ` `"The angle of elevation for line PQ is: "` ` ` `<< arg(Q-P)*(180/PI) << ` `" degrees"` `<< endl;` ` ` `cout << ` `"The slope of line PQ is: "` `<< ` `tan` `(arg(Q-P)) <<endl;` ` ` ` ` `// Construction of point A` ` ` `point A = conj(P)*Q;` ` ` ` ` `// Dot Product and Cross Product` ` ` `cout << ` `"The dot product P.Q is: "` `<< A.x << endl;` ` ` `cout << ` `"The magnitude of cross product PxQ is: "` `<< ` `abs` `(A.y) << endl;` ` ` ` ` `return` `0;` `}` |

Output:

Addition of P and Q is: P+Q(5, 7) Subtraction of P and Q is: P-Q(-1, -1) The distance between point P ans Q is: 1.41421 The squared distance between point P ans Q is: 2 The angle of elevation for line PQ is: 45 degrees The slope of line PQ is: 1 The dot product P.Q is: 18 The magnitude of cross product PxQ is: 1

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