On Sat, 17 May 2014 16:18:07 -0400, FG <[email protected]> wrote:
On 2014-05-17 21:35, bearophile wrote:
FG:
and don't forget the extra memory needed to store the tree for fast
key look-up in the hash array.
I think D now uses a linked list for the collision chains (so opCmp is
useless, despite it's still required for the hashing protocol).
Indeed, I just read
https://github.com/D-Programming-Language/dmd/blob/master/src/backend/aa.c
This is dmd's source, not druntime. This is the representation of AA's in
the compiler, not in your code. The appropriate code for druntime is here:
https://github.com/D-Programming-Language/druntime/blob/master/src/rt/aaA.d
Key hash is divided modulo the number of buckets and each bucket points
to an ordered double-linked list. That list is walked left or right
depending on what value Typeinfo::compare returns for two keys. Hmm...
isn't opCmp used by that function? Why useless?
No, in that DMD file, the bucket is a tree, not a doubly-linked list.
opCmp is not used in D's AA. The D implementation used to mirror DMD, but
it does not any more.
It may be used for CTFE, I'm not sure.
-Steve
