if(j != i) {
        f[i][j] = physics.makeAttraction(p[i], p[j], k, 1);
      }
      else {
        f[i][j] = physics.makeAttraction(p[i], p[j], 0.0, 0.0);
      }
  

import traer.physics.*;

int n = 10, k = -5;
ParticleSystem physics;
Particle[] p = new Particle[n], a = new Particle[n];
Spring[] s = new Spring[n];
Attraction[][] f = new Attraction[n][n];

void setup() {
  size(400,400);
  smooth();
  fill(255, 200);
  stroke(255, 200);
  ellipseMode( CENTER );

  physics = new ParticleSystem( 1, 0.05 );

  for(int i = 0; i < n; i++) {
    p[i] = physics.makeParticle( 1.0, width/2, height/2, 0 );
    a[i] = physics.makeParticle( 1.0, random(0,width), height/2, 0 );

    a[i].makeFixed();
    s[i] = physics.makeSpring( p[i], a[i], 0.5, 0.1, 75 ); // Connects anchor to particle
  }
  // If this is commented out then the pde runs---Start
  // Create an attraction between all free particles
  for(int i = 0; i < n; i++) {
    for(int j = 0; j < n; j++) {
      if(j != i) {
        f[i][j] = physics.makeAttraction(p[i], p[j], k, 1);
      }
    }
  }
  // If this is commented out then the pde runs---End

}

void draw() {
  physics.tick();

  //background( 51, 181, 74 ); // Green
  background( 0, 182, 235 ); // Cyan

  for(int i = 0; i < n; i++) {
    line( p[i].position().x(), p[i].position().y(), a[i].position().x(), a[i].position().y() );
    ellipse( a[i].position().x(), a[i].position().y(), 5, 5 );
    ellipse( p[i].position().x(), p[i].position().y(), 20, 20 );
  }
}