gasket := proc (a,b,L,k,m) 
  description `returns Sierpinski's triangular curve`;
  local p, np;
  p := [];
  if k = 0 then
    p := [plots[polygonplot]([[a,b],[a+L,b],[a,b+L]],style = line)]:
  end if;
  np := plots[polygonplot]([[a,b+1/2*L],[a+1/2*L,b],[a+1/2*L,b+1/2*L]],
                           color = green);
  p := [op(p),np];
  if k < m then
    np := gasket(a,b,1/2*L,k+1,m); p := [op(p),op(np)];
    np := gasket(a,b+1/2*L,1/2*L,k+1,m); p := [op(p),op(np)];
    np := gasket(a+1/2*L,b,1/2*L,k+1,m); p := [op(p),op(np)];
  end if;
  return p;
end proc;