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Re: the unsigned right shift operator in CL >>>

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Aidan Kehoe <kehoea@parhasard.net> writes:

    Ar an cúigiú lá déag de mí Deireadh Fómhair, scríobh Madhu: 

   Something like:

   (defun fixed-width-ash (width value count)
     (ash (logand value (lognot (ash -1 width))) count))

   Construct an integer of the desired width that is all 1s, logand it
   with VALUE, then shift by COUNT.

Your compiler will probably recognize that this is equivalent to:

   (defun fixed-width-ash (width value count)
     (ash (logandc2 value (ash -1 width)) count))

But I would write it that way in the first place because I like to
remember that the PDP-10 had an ANDCM instruction...

-- 
Alan Bawden

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Thread

the unsigned right shift operator in CL >>> Madhu <enometh@meer.net> - 2025-10-15 12:34 +0530
  Re: the unsigned right shift operator in CL >>> Aidan Kehoe <kehoea@parhasard.net> - 2025-10-16 19:04 +0100
    Re: the unsigned right shift operator in CL >>> Alan Bawden <alan@csail.mit.edu> - 2025-10-16 16:06 -0400
      Re: the unsigned right shift operator in CL >>> Aidan Kehoe <kehoea@parhasard.net> - 2025-10-16 21:55 +0100
        Re: the unsigned right shift operator in CL >>> Madhu <enometh@meer.net> - 2025-10-23 16:34 +0530
          Re: the unsigned right shift operator in CL >>> Alan Bawden <alan@csail.mit.edu> - 2025-10-24 02:29 -0400
            Re: the unsigned right shift operator in CL >>> Madhu <enometh@meer.net> - 2025-10-25 21:00 +0530
            Re: the unsigned right shift operator in CL >>> Kaz Kylheku <046-301-5902@kylheku.com> - 2026-03-12 18:00 +0000
              Re: the unsigned right shift operator in CL >>> Stefan Monnier <monnier@iro.umontreal.ca> - 2026-03-12 16:34 -0400
                Re: the unsigned right shift operator in CL >>> Kaz Kylheku <046-301-5902@kylheku.com> - 2026-03-16 20:14 +0000
  Re: the unsigned right shift operator in CL >>> Madhu <enometh@meer.net> - 2025-10-23 16:38 +0530

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