16:10 < Bike> simple-array definition question. clhs make-array says that if :displaced-to is nil, the new array is not a
displaced array. but clhs array-displacement says it can, depending on implementation, return something for
arrays that were made with :displaced-to nil
16:10 < Bike> am i missing something here
16:15 < phoe> clhs make-array
16:15 < specbot> http://www.lispworks.com/reference/HyperSpec/Body/f_mk_ar.htm
16:15 < phoe> "If make-array is called with adjustable, fill-pointer, and displaced-to each nil, then the result is a simple
array."
16:16 < phoe> oh wait. wrong quote.
16:16 < beach> Bike: See the Cleanup issue.
16:17 < beach> Some implementations implicitly displace some arrays. (For example, adjustable arrays might be represented as
displaced arrays.) Permitting ARRAY-DISPLACEMENT to return non-NIL for those arrays allows those
implementations not to have to record some additional information in the array about whether an explicit
:DISPLACED-TO was provided.
16:17 < beach>
16:17 < beach>
16:17 < beach>
16:17 < beach> Oops, sorry.
16:18 < Bike> That's what I thought, but I don't understand how that's allowed by the definition of make-array
16:18 < Bike> which cleanup issue do you mean?
16:18 < beach> Bottom of the page on array-displacement.
16:19 < beach> If you pass :adjustable t, then the implementation may create a displaced array.
16:19 < beach> clhs array-displacement
16:19 < specbot> http://www.lispworks.com/reference/HyperSpec/Body/f_ar_dis.htm
16:19 < beach> http://www.lispworks.com/documentation/HyperSpec/Issues/iss132.htm
16:19 < beach> http://www.lispworks.com/documentation/HyperSpec/Issues/iss132_w.htm
16:22 < Bike> i understand that, what i don't get is the apparently clear prohibition on make-array: "If displaced-to is nil,
the array is not a displaced array."
16:23 < Bike> is that just wrong? or does "displaced array" not mean "array that returns something from array-displacement"?
16:23 < beach> The latter.
16:24 < Bike> oh, okay.
16:24 < beach> But, honestly, I think they got it wrong. The two pages were probably written at different times.
16:24 < Bike> okay.
16:25 < beach> Note to self: Define "displaced array" better in WSCL.
