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Re: Growable arrays?

From: Daniel Hartwig
Subject: Re: Growable arrays?
Date: Thu, 14 Jun 2012 23:23:59 +0800

On 14 June 2012 22:47, David Kastrup <address@hidden> wrote:
> Mark H Weaver <address@hidden> writes:
>> David Kastrup <address@hidden> writes:
>>> Scheme/Guile vectors are fixed size.  [...]  It is a bit of a nuisance
>>> that one can grow a hashtable efficiently and on-demand, but not so an
>>> array.
>> Although Scheme vectors should remain fixed-size for reasons I have
>> given elsewhere in this thread, Guile also includes a more complex
>> 'array' type that includes features such as arbitrary rank (i.e. number
>> of dimensions), arbitrary lower bounds (not just 0), and shared views on
>> the same underlying array with arbitrary affine mappings of indices.
>> Guile 'arrays' cannot currently be resized, but I see no good reason for
>> this limitation.  They are already quite complex, and already require a
>> second level of pointer indirection.
>> What do other people think?

Perhaps drop a basic resizable type in the guile-lib?  Any
implementation is going to be less-than-ideal in some situations. The
guile core provides already a solid set of fundamental types which are
very easy to compose to produce *exactly* the type required for any
particular situation.

> Another complex type, this time with quite more serious memory and
> performance impact, that can't be implemented on top of a simple
> resizable common primitive and has an almost, but not quite, overlapping
> underlying feature set?
> It's almost as if you _like_ not being able to reuse code.

I don't see how either hash table or multi-dimensional array type
could benefit from a shared, resizable primitive – they are quite
different algorithms, and both different again to the basic resizable
vector already discussed.

It is moot that hash table internally manages a vector and allocates a
/new/ vector when needed.  This is not a simple resizing operation.

Are there any data types in the guile core which would benefit from
sharing a resizable vector primitive?

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