[racket] case form implemented with a hash

From: Jos Koot (jos.koot at telefonica.net)
Date: Wed Sep 28 16:55:08 EDT 2011

Hi Hatthew,
I am still trying to implement 'case' by means of a hash.
Can you give me a more specific pointer. I followed your pointer but did not
see anything relevant to my question.

-----Original Message-----
From: Matthew Flatt [mailto:mflatt at cs.utah.edu] 
Sent: miércoles, 28 de septiembre de 2011 22:20
To: Jos Koot
Cc: 'Racket-users'
Subject: Re: [racket] case form implemented with a hash

At Wed, 28 Sep 2011 22:08:44 +0200, "Jos Koot" wrote:
> By inspection with the macro stepper I found that case forms are expanded
> nested if-forms. For case forms with many clauses, this may be
> I have tried to prepare a hash-case form using a hash table in order to
> select the desired clause more efficiently. So far my attempts failed. I
> still trying. However, has anybody else on this list thought of using a
> for case forms with many clauses? Does it exist? If not, would anyone be
> interested in a hash-case form that has the same shape as a case-form, but
> uses a hash-table to select the appropriate clause? The hash table should
> a map onto thunks and macro hash-case simply would have to retrieve the
> thunk and call it.

See "Rapid Case Dispatch in Scheme", Clinger, Scheme'06.

If you implement a revised `case' that consistently works better, then
I'd be happy to use it as a replacement for the current `case'.

Posted on the users mailing list.