On Fri, Jan 21, 2011 at 6:43 PM, Aaron Cohen <aa...@assonance.org> wrote:
>> max-key uses destructuring, which was one of the culprits for
>> unexpectedly holding onto the head of lists before locals clearing was
>> added.
>
> This part of what I said is garbage, I'm sorry. I looked at max-key
> too quickly, but there isn't any destructuring there.
I wrote my own implementation of max-key that doesn't use
destructuring before reading the later part of this thread. :)
It is here:
(defn my-max-key [f & xs]
(reduce
(fn [v1 v2]
(let [k1 (f v1)
k2 (f v2)]
(if (> k1 k2)
v1
v2)))
xs))
If the original code had blown the heap on my machine I was going to
substitute my-max-key and see if it still did, and if it did tweak
my-max-key to see if there was a way to make the problem go away.
This my-max-key is less than perfectly efficient in that it keeps
recomputing f of the current max-key; it's a no-frills version
intended to be sure not to hold onto the head of anything, and to be
simple and easy to tweak and debug. I'd have added saving f of current
max-key later and seen if it still avoided blowing the heap on the
original problem, and, if so, submitted it as a possible replacement
for the core implementation of max-key. But that's moot now. It looks
like one of the improvements to locals clearing in 1.2 fixed the OP's
problem.
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