- :WEAK-P -- (This is an extension from CMU CL, not currently supported
- in SBCL 0.6.6, but perhaps supported in a future version.) If T,
- don't keep entries if the key would otherwise be garbage."
+ :WEAKNESS -- IF NIL (the default) it is a normal non-weak hash table.
+ If one of :KEY, :VALUE, :KEY-AND-VALUE, :KEY-OR-VALUE it is a weak
+ hash table.
+ Depending on the type of weakness the lack of references to the
+ key and the value may allow for removal of the entry. If WEAKNESS
+ is :KEY and the key would otherwise be garbage the entry is eligible
+ for removal from the hash table. Similarly, if WEAKNESS is :VALUE
+ the life of an entry depends on its value's references. If WEAKNESS
+ is :KEY-AND-VALUE and either the key or the value would otherwise be
+ garbage the entry can be removed. If WEAKNESS is :KEY-OR-VALUE and
+ both the key and the value would otherwise be garbage the entry can
+ be removed."