+ Real my_extent= is_empty () ? 0.0 : dim_[a][d];
+ Interval i (m.extent (a));
+ Real his_extent;
+ if (i.is_empty ())
+ {
+ programming_error ("Molecule::add_at_edge: adding empty molecule.");
+ his_extent = 0.0;
+ }
+ else
+ his_extent = i[-d];
+
+ Real offset = (my_extent - his_extent) + d*padding;
+ if (minimum > 0 && fabs (offset) < minimum)
+ offset = sign (offset) * minimum;
+
+ Molecule toadd (m);
+ toadd.translate_axis (offset, a);
+ add_molecule (toadd);