[debbugs-tracker] bug#18224: closed (Shared arrays are incompatible with bytevector accessors)

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Your message dated Fri, 30 Oct 2015 17:15:21 +0100
with message-id <address@hidden>
and subject line Re: bug-guile Digest, Vol 137, Issue 2
has caused the debbugs.gnu.org bug report #18224,
regarding Shared arrays are incompatible with bytevector accessors
to be marked as done.

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-- 
18224: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=18224
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> --- Begin Message ---
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> Subject: 
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> Shared arrays are incompatible with bytevector accessors
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> Date: 
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> Fri, 8 Aug 2014 16:48:08 +0200
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> Creating a shared array based on a bytevector results with an object
> whose print representation is identical with a print-representation of
> a bytevector:
>
> (define bv #vu8(0 1 2 3))
>
> (define bv/shared
>   (make-shared-array bv (lambda(i)(list (+ i 2))) '(0 1)))
> bv/shared
> ====> #vu8(2 3)
>
> However, accessing these "shared bytevectors" using the bytevector api
> is impossible:
>
> (bytevector-u8-ref bv/shared 0)
> ====> error: wrong type argument in position 1 (expecting bytevector): #vu8(2 3)
>
> Since the print-representation is identical, this behaviour is
> unexpected. Furthermore, the lack of capability of creating shared
> bytevectors limits their usefullness. On the other hand, if the shared
> bytevector remains contiguous, there should be no performance
> concerns.
>
>
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> --- End Message ---
> --- Begin Message ---
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> Subject: 
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> Re: bug-guile Digest, Vol 137, Issue 2
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>
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> Date: 
>
> Fri, 30 Oct 2015 17:15:21 +0100
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> http://git.savannah.gnu.org/gitweb/?p=guile.git;a=commitdiff;h=eb3d623da57e6d31a58d95f932345fb761f9b701
>  on master fixes printing of scm_tc7_array (shared array) to be #1(...) or 
> #1typetag(...) so they aren't confused with actual vectors or bytevectors.
>
> With respect to the lack of capability to create shared bytevectors, use the 
> array procedures instead. If you need the arrays to be contiguous, you can 
> check this at run time.
>
> The fundamental distinction between shared arrays on one side and 
> bytevectors/vectors/bitvectors on the other side is not of contiguity, rank, 
> element type, etc. but that the latter types are containers, while the shared 
> arrays are just views. That is why I don't think indirection fields should be 
> added to the bytevectors, this would complicate the lookup functions and 
> overlap in functionality with arrays.
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> --- End Message ---