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Adjusting Displaced Arrays
- To: common-lisp@su-ai
- Subject: Adjusting Displaced Arrays
- From: greek@DEC-HUDSON
- Date: Wed, 12 Jun 85 09:29:57 EDT
I'll accept the hair of allowing arbitrary "nesting" of displaced arrays,
but I don't have to like it.
Unless I missed a message, I still don't understand some things.
1. CLtL says that if the :DISPLACED-TO option is specified on ADJUST-ARRAY
then none of the original contents of the array appears in the new
array. I presume, of course, that this is not the case when displacing
back to the original target array, which I have to explicitly request
according to the first paragraph on page 298.
2. Moon stated that adjusting an array never affect the target array.
Assuming my point #1 is correct, then the target array is affected
if a) it is specified in the :DISPLACED-TO option, and b) the
:INITIAL-ELEMENT option is also specified.
If I'm incorrect here, then I think that implies that the new array
has to share some element with the original target array and also
have some of its own!
The reason we chose not to implement adjustable displaced arrays in VAX
LISP was not because we have a religious objection, but because I
didn't understand what to do. I guess I'd like to see a list of all
the options to ADJUST-ARRAY and what they do to displaced arrays.
We also need to specify any interactions between the options, such
as with :DISPLACED-TO AND :INITIAL-ELEMENT above.