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From: ForthNet@willett.pgh.pa.us (ForthNet articles from GEnie)
Newsgroups: comp.lang.forth
Subject: Conventions and "tricks" used in Forth
Message-ID: <1936.UUL1.3#5129@willett.pgh.pa.us>
Date: 28 Oct 90 17:36:43 GMT
Organization: String, Scotch tape, and Paperclips.  (in Pgh, PA)
Lines: 23


   To: IAN WATTERS                   Refer#: 4094
 From: RAY DUNCAN                      Read: NO
 Subj: CONVENTIONS AND "TRICKS"      Status: PUBLIC MESSAGE
 Forgetting is no problem.  To FORGET a word, we find it via the hash
 table, truncate the header segment at that point (thereby also
 discarding all subsequently defined words), then rebuild the hash table
 from scratch.  The routine which builds the hash table is all in
 assembler and very tightly coded, so the user never notices any delay
 after FORGET; the only other time you have to build the whole hash table
 is at boot, and that delay is hidden inside the Forth system's load
 time.

 Collisions are chained, but the chains tend to be very short; even with
 a couple thousand words in the dictionary, the average chain length is
 less than 2. 

 In a way this is the extreme case of the multithreaded dictionary!

 NET/Mail : LMI Forth Board, Los Angeles, CA (213) 306-3530             
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