import graph;
size(200,IgnoreAspect);

real f(real x) {return 1/x;};

bool3 branch(real x)
{
  static int lastsign=0;
  if(x == 0) return false;
  int sign=sgn(x);
  bool b=lastsign == 0 || sign == lastsign; 
  lastsign=sign;
  return b ? true : default;
}

draw(graph(f,-1,1,branch));
axes("$x$","$y$",red);