Arguments

ename  (ename, optional) the entity to be added to the specified or new selectionset;
if omitted, a new empty selectionset is created

selectionSet  (pickset [ename], optional) the selectionset to add the entity to;
if omitted, a new selectionset is created

Return

ENAME, the newly created or passed-in selectionSet, or NIL if it fails

Example

(ssadd)  <Selection set: 00000000401F7980>  new empty selectionset
(ssadd (entlast))  <Selection set: 00000000401F7980>  new selectionset, containing the (entlast) entity
(ssadd (entlast) ss)  <Selection set: 00000000401F7980>  modified the passed-in selectionset ss, extended by

Remarks

adding an entity, which is already contained in a selectionset will not modify the selectionset (each entity is contained only once);
only entities are allowed in a selectionset, non-graphical objects are not allowed