inv_hooke += springs_[i].inverse_stretch_strength ();
if (inv_hooke == 0.0) /* avoid division by zero. If springs are infinitely stiff */
- return 0.0; /* anyway, then it makes no difference what the force is */
+ inv_hooke = 1e-6; /* then report a very large stretching force */
assert (cur_len <= line_len_);
return (line_len_ - cur_len) / inv_hooke + force_;