#include <GL/glut.h>
#include <cmath>

#define PI 3.14159265358979323846

// Struct to define a planet
struct Planet {
    float distance;  // Distance from the sun
    float angle;     // Current angle in the orbit
    float speed;     // Orbital speed
    float radius;    // Radius of the planet
    float r, g, b;   // Color of the planet
};

Planet planets[] = {
    { 20.0, 0.0, 0.1, 2.0, 1.0, 0.0, 0.0 },   // Planet 1
    { 30.0, 0.0, 0.07, 1.5, 0.0, 1.0, 0.0 },  // Planet 2
    { 40.0, 0.0, 0.05, 1.8, 0.0, 0.0, 1.0 }   // Planet 3
};

// Function to draw a circle
void drawCircle(float radius, int segments) {
    glBegin(GL_POLYGON);
    for (int i = 0; i < segments; i++) {
        float theta = 2.0f * PI * float(i) / float(segments);
        float dx = radius * cosf(theta);
        float dy = radius * sinf(theta);
        glVertex2f(dx, dy);
    }
    glEnd();
}

// Display callback function
void display() {
    glClear(GL_COLOR_BUFFER_BIT);
    glLoadIdentity();

    // Draw the sun
    glColor3f(1.0, 1.0, 0.0);  // Yellow color
    drawCircle(5.0, 50);       // Sun with radius 5.0

    // Draw the planets
    for (auto& planet : planets) {
        glPushMatrix();
        glRotatef(planet.angle, 0.0, 0.0, 1.0);
        glTranslatef(planet.distance, 0.0, 0.0);
        glColor3f(planet.r, planet.g, planet.b);
        drawCircle(planet.radius, 20);
        glPopMatrix();

        // Update the planet's angle for the next frame
        planet.angle += planet.speed;
        if (planet.angle > 360.0) {
            planet.angle -= 360.0;
        }
    }

    glutSwapBuffers();
}

// Reshape callback function
void reshape(int w, int h) {
    glViewport(0, 0, (GLsizei)w, (GLsizei)h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(-50.0, 50.0, -50.0, 50.0);
    glMatrixMode(GL_MODELVIEW);
}

// Timer callback function
void timer(int) {
    glutPostRedisplay();
    glutTimerFunc(16, timer, 0);
}

// Main function
int main(int argc, char** argv) {
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
    glutInitWindowSize(800, 800);
    glutCreateWindow("Solar System Simulation");

    glutDisplayFunc(display);
    glutReshapeFunc(reshape);
    glutTimerFunc(0, timer, 0);

    glClearColor(0.0, 0.0, 0.0, 1.0);  // Black background

    glutMainLoop();
    return 0;
}
 
by

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Read inputs from stdin

OneCompiler's C++ online compiler supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample program which takes name as input and print your name with hello.

#include <iostream>
#include <string>
using namespace std;

int main() 
{
    string name;
    cout << "Enter name:";
    getline (cin, name);
    cout << "Hello " << name;
    return 0;
}

About C++

C++ is a widely used middle-level programming language.

  • Supports different platforms like Windows, various Linux flavours, MacOS etc
  • C++ supports OOPS concepts like Inheritance, Polymorphism, Encapsulation and Abstraction.
  • Case-sensitive
  • C++ is a compiler based language
  • C++ supports structured programming language
  • C++ provides alot of inbuilt functions and also supports dynamic memory allocation.
  • Like C, C++ also allows you to play with memory using Pointers.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition If-Else is used.

if(conditional-expression) {
   //code
}
else {
   //code
}

You can also use if-else for nested Ifs and If-Else-If ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to If-Else-If ladder.

switch(conditional-expression){    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
......    
    
default:     
 code to be executed when all the above cases are not matched;    
} 

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  //code  
} 

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while (condition) {  
// code 
}  

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {  
 // code 
} while (condition); 

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity. Function gets run only when it is called.

How to declare a Function:

return_type function_name(parameters);

How to call a Function:

function_name (parameters)

How to define a Function:

return_type function_name(parameters) {  
 // code
}