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Re: [MIT-Scheme-devel] weak hash table data
From: |
Taylor R Campbell |
Subject: |
Re: [MIT-Scheme-devel] weak hash table data |
Date: |
Tue, 22 Dec 2009 08:59:04 -0500 |
User-agent: |
IMAIL/1.21; Edwin/3.116; MIT-Scheme/7.7.90.+ |
Date: Tue, 22 Dec 2009 02:04:03 -0800
From: Chris Hanson <address@hidden>
This is incorrect. GC marks every table as needing rehash; the next
access to that table forces a rehash, which cleans the table.
Right, although HASH-TABLE/DATUM-LIST and friends don't count as
`access'. Still, weak hash tables that are not in frequent use will
not be cleaned, nor will weak hash tables that are not GC-sensitive.
For example, a weak hash table keyed by symbols with SYMBOL-HASH as
its hash function rather than EQ-HASH (or one keyed by URIs with
(COMPOSE STRING-HASH URI->STRING) as its hash function, since interned
symbols are now held strongly as keys).