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- To: RWK at MIT-MC
- Subject: LAST
- From: HIC at MIT-MC (Howard I. Cannon)
- Date: Wed, 6 Sep 78 03:40:00 GMT
- Cc: (BUG LISP) at MIT-MC, CWH at MIT-MC
- Original-date: 5 SEP 1978 2340-EDT
From: RWK at MIT-MC (Robert W. Kerns)
Your comment would be almost valid, except that LAST obviously isn't
just CDR'ing down the list checking for NIL. It is doing a LIST-P
on the CDR instead.
You are wrong. It is doing a NIL check (look at the damn code before
After all, this isn't very expensive, a MOVEI, a LSH,
and a SKIPL will do it. I would muchly appreciate it if APPEND would
be changed to do likewise.
Compared to a JUMPN, a MOVEI, LSH, and SKIPL are quite expensive.
(There should also be a TYPEP before the loop,
so (LAST 3.3) wouldn't die).
I had this idea also, and I might implement it.
After all, the interpreter isn't supposed to
be fast, it's supposed to be suportive and not die on easy mistakes.
This is true...on the other hand, one does not want to make it unbearably slow.
Perhaps a *RSET check is in order...more thought is necessary.