On Sun, May 26, 2013 at 7:49 AM, Alexey Radul <[email protected]> wrote:
>
> 2) Universal lookup procedure
>
> I am fond of the following universal lookup procedure [1]:
> (hash-table-search table key
> (lambda (value update remove)
> ...)
> (lambda (insert)
> ...))
>
This is very nice, and it's important to provide fundamental
operations such as this which allow arbitrary ref+update logic
without requiring the hash to be recomputed. This is not
possible in either the SRFI-69 or R6RS APIs (though an impl
may cache one or more recently hashed values).
I also think the following utility is nice, as there is no other
existing utility to use a hash-table as a cache with a single
operation:
(hash-table-ref/cache! table key thunk)
=> (hash-table-search
table key
(lambda (value update remove)
value)
(lambda (insert)
(let ((res (thunk)))
(insert res)
res)))
--
Alex
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