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*To*: common-lisp at SU-AI*Subject*: Comment on HAULONG*From*: Guy.Steele at CMU-10A*Date*: Thu, 08 Jul 1982 02:44:00 -0000

What do people think of the following suggested change? I suspect MacLISP HAULONG was defined as it was because internally it used sign-magnitude representation. EAK's suggestion is more appropriate for two's-complement, and the LOGxxx functions implicitly assume that as a model. - - - - Begin forwarded message - - - - Mail-From: ARPANET host MIT-Multics received by CMU-10A at 7-Jul-82 17:03:29-EDT Date: Wed, 07 Jul 1982 17:52:00 -0000 From: Earl A. Killian <Killian at MIT-MULTICS> Subject: haulong To: Guy Steele at CMUa I think the definition in the manual for haulong: ceiling(log2(abs(integer)+1)) is poor. Better would be if integer < 0 then ceiling(log2(-integer)) else ceiling(log2(integer+1)) I know of no non-conditional expression for this haulong (if you should ever discover one, please let me know). The only numbers that this matters for are -2^N. Amusingly enough, I found this exact bug in the two compilers I've worked on (i.e. they thought it took 9 bits instead of 8 to store a -256..255). - - - - End forwarded message - - - -

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