Data.HashTable and duplicate keys
simonmar at microsoft.com
Tue Sep 28 08:03:20 EDT 2004
On 28 September 2004 12:49, George Russell wrote:
> Einar wrote (snipped):
> > I recently noticed that Data.HashTable silently
> > accepts duplicate keys and keeps all the values.
> > This is very counterintuitive from the interface
> > and makes updating a hashtable quite tedious
> > (lookup + delete + insert).
> Gosh, I'm glad *someone* told me of this bizarre behaviour.
> Why on earth hash tables should mimic association lists of
> all things is a mystery to me. (Should GHC also insert
> delay loops to simulate their poor performance?)
> Sigh, off I go to fix my code. Just as well I only use
> hash tables in one place.
Making insert do delete+insert is pretty inefficient if you know that
the key isn't in the table. Providing update (==delete+insert) seems a
reasonable solution, no?
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