Re: [Ocaml-lib-devel] Re: Array interface

[John M. S. <sk...@oz...>]

Yamagata Yoriyuki wrote:

> From: Alan Post <ap...@re...>
> Subject: [Ocaml-lib-devel] Re: Array interface
> Date: Fri, 20 Jun 2003 23:56:25 +0000 (UTC)
> 
> 
>>What is under discussion is what to put in the "empty" slots of the
>>newly doubled array, ocaml having no "null" or "undef" value to stuff
>>in them.
>>
> 
> I do not understand the motive of Dynarray,


Variable length array with automatic efficient resizing.
It needs to allocate more store than the number of
slots actually needed to minimise reallocation
on extension of the array, and allow contraction
without necessarily reallocating.

So there are some slots of the underlying array
that are unused. The problem is how to fool
the garbage collector without a dummy object
to put in the unused slots.

The client may not be able to construct an object
of the right type easily, and copying a real
element may create references that prevent the
collector removing an object -- unless the design
carefully refills unused slots with the value
of a used slot -- and destroys the array completely
when no slots are used.

Therefore, there is no really good design 'in ocaml':
Dynarray is really a system primitive.

Hmmm.. it was said a C implementation should use VALUE
macro not integer 0. A small C interface will make
that available as a universal NULL value?

I guess this is a C null pointer: ie, an address the collector
will leave alone, rather than an integer the collector
will leave alone?

-- 
John Max Skaller, mailto:sk...@oz...
snail:10/1 Toxteth Rd, Glebe, NSW 2037, Australia.
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