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[Caml-list] how to use functors?
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Date: 2005-11-22 (15:22)
From: Christophe Raffalli <christophe.raffalli@u...>
Subject: Re: [Caml-list] how to use functors?
Jonathan Roewen a écrit :
> Hi,
> Prolly the wrong list, but I can't access's documentation ATM =/
> How do I use a functor? For example: build a weak hashtable from Weak
> module? Seems useful for building a cache... if only I knew how to use
> it =P
> Jonathan

You want weak key, weak vailue or both ?

I mean you want the binding in the hashtbl to disappear when the key is 
no more GC accessible, the value of both ?

Let us assume you want key-weak ...

This is not completely trivial to do what you want from the Weak module 
and this is not a problem of functor ...

A way to do that is to do build a weak array for the key, with a 
hashtable algorithm for the index (the position of the key in the array
depends upon the hash function)

Then you put the associated value in a separate non weak array, at the 
same index than the key.

Finaly, you also put a finaliser on the key to erase the associated 
value when the key is collected by the GC ...

I hope this help ... and I think weak hashtbl should be provided by the
language ...

Christophe Raffalli
Université de Savoie
Batiment Le Chablais, bureau 21
73376 Le Bourget-du-Lac Cedex

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