+ if (distance <= 0.0 || inverse_strength < 0.0)
+ {
+ programming_error ("adding reverse spring, setting to unit");
+ distance = 1.0;
+ inverse_strength = 1.0;
+ }
+
+ if (isinf (distance) || isnan (distance)
+ || isnan (inverse_strength))
+ {
+ /* strength == INF is possible. It means fixed distance. */
+ programming_error ("insane distance found");
+ distance = 1.0;
+ inverse_strength = 1.0;
+ }
+