[toronto-lisp] March meeting minutes.

[Vishvajit Singh]

I found a (supposedly) complete version.. it's really a terrifying
thing to behold..

http://www.cliki.net/SHALLOW-COPY-ARRAY

Preserves fill-pointer, element-type, adjustable-p, and displacement..

-vish

On Wed, Mar 10, 2010 at 10:31 PM,  <doug at hcsw.org> wrote:
> On Tue, Mar 09, 2010 at 10:12:32PM -0500 or thereabouts, Abram Hindle wrote:
>> Well if I use copy-seq I get this error from sbcl:
>>
>> unhandled TYPE-ERROR in thread #<SB-THREAD:THREAD "initial thread"
>> RUNNING {10026F2EC1}>:
>>   The value
>>     #2A((#\# #\# #\# #\#)
>>         (#\# #\1 #\  #\#)
>>         (#\# #\# #\  #\#)
>>         (#\# #\  #\  #\#)
>>         (#\# #\2 #\# #\#)
>>         (#\# #\# #\# #\#))
>>   is not of type
>>     SEQUENCE.
>
> Ya like I said in my last message that was my mistake. I meant to say
> vectors are sequences so can be copied with copy-seq. Arrays are not
> sequences.
>
>
>> (defun copy-array (array)
>> ;  (copy-seq array))
>>   (let ((dims (array-dimensions array)))
>>     (adjust-array
>>      (make-array dims :displaced-to array)
>>      dims)))
>>
>> Where as this does not.
>
> Nice one though it might be a good idea to propagate the element type too
> so stuff like this doesn't happen:
>
> * (make-array '(2 2) :element-type '(unsigned-byte 8))
>
> #2A((0 0) (0 0))
>
> * (copy-array *)
>
> Error in function MAKE-ARRAY:
>   One can't displace an array of type T into another of type (UNSIGNED-BYTE 8).
>   [Condition of type SIMPLE-ERROR]
>
>
> I think this is a bit better (but probably still isn't complete because
> of not copying fill pointers and whatnot):
>
> (defun copy-array (array)
>  (let ((dims (array-dimensions array)))
>    (adjust-array
>     (make-array dims :displaced-to array
>                      :element-type (array-element-type array))
>     dims)))
>
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