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N-body simulator C++ code

//C++ code snippets for an N-body simulator
//Uses a very simple single-step iterative method.
//In my opinion if you want to write an n-body simulator,
// its best to start with a simple method like this,
// (and change to a better method after you've got everything working).
//Please note this is not a complete program, just the core functions
//The top-level function is SSystem::CalcAll(), it calls all the other functions
//Website: http://www32.brinkster.com/snefru/space

bool SSystem::CalcAll()
{
   PullAll();
   MoveAll();
   return(true);
}

bool SSystem::PullAll()
{
   double DistX, DistY, DistZ, Dist, DistSquared;
   double GravX, GravY, GravZ, Grav;
   //for each permutation of two stars
   for(int i=0; iPosX-Body[i]->PosX;
         DistY=Body[j]->PosY-Body[i]->PosY;
         DistZ=Body[j]->PosZ-Body[i]->PosZ;
         DistSquared=DistX*DistX+DistY*DistY+DistZ*DistZ;
         Dist=sqrt(DistSquared);
         //body i attracts body j
         if(Body[i]->MassFlag)
         {
             Grav=Body[i]->Mass*GravConst/DistSquared;
             GravX=Grav*DistX/Dist;
             GravY=Grav*DistY/Dist;
             GravZ=Grav*DistZ/Dist;
             Body[j]->VelX+=GravX*Step;
             Body[j]->VelY+=GravY*Step;
             Body[j]->VelZ+=GravZ*Step;
         }
         //body j attracts body i
         if(Body[j]->MassFlag)
         {
            Grav=Body[j]->Mass*GravConst/DistSquared;
            GravX=-Grav*DistX/Dist;
            GravY=-Grav*DistY/Dist;
            GravZ=-Grav*DistZ/Dist;
            Body[i]->VelX+=GravX*Step;
            Body[i]->VelY+=GravY*Step;
            Body[i]->VelZ+=GravZ*Step;
         }
      }
   }
   return(true);
}

bool SSystem::MoveAll()
{
   for(int i=0; iMove();
   return(true);
}

bool SBody::Move()
{
   PosX+=VelX*TheSystem->Step;
   PosY+=VelY*TheSystem->Step;
   PosZ+=VelZ*TheSystem->Step;
   return(true);
}

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