Re: =?ISO-8859-1?Q?what's_"weakness"_in_elisp's_hash_table??=

[Tim X]

Xah Lee <xah@xahlee.org> writes:

> in emacs lisp, when creating a hash table, there's the “:weakness”
> thing.
>
> See
> http://xahlee.org/elisp/Creating-Hash.html
>
> what does that mean? Suppose if i do
>
>   (setq myhash (make-hash-table :test 'equal :weakness 'key))
>   (puthash "mary" "19" myhash)
>   ...
>
> Then, the "mary" would disappear if i don't access it??
>

The entry with key 'mary' and value 19 will be removed from the hash table
if it has no references i.e. it will be garbage collected. Normally, with
:weakness set to nil, keys and values in a hash table are protected from
garbage collection. 



-- 
tcross (at) rapttech dot com dot au