Groups > comp.lang.java.programmer > #3268

Re: Java left shift and right shift operators.

From	Lew <noone@lewscanon.com>
Newsgroups	comp.lang.java.programmer
Subject	Re: Java left shift and right shift operators.
Date	2011-04-26 11:24 -0400
Organization	albasani.net
Message-ID	<ip6o3a$lc$1@news.albasani.net> (permalink)
References	<295e16b3-2ed8-4529-bfb0-1cc26ed93ad6@d26g2000prn.googlegroups.com> <1b558330-ae94-4e4e-9922-a9aeb63eaf37@d19g2000prh.googlegroups.com> <ip6kuf$5g4$1@dont-email.me>

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Travers Naran wrote:
> Sanny wrote:
>>> Is there any way to avoid the if condition and do right shift and left
>>> shift using operators depending on shiftby is +ve or -ve?
>>
>> I used below technique but it gives error.
>>
>> divider=Math.pow(2,shiftby);

Please follow Java naming conventions.

>> then
>> output = (long) N / divider;

> My advice:
> if (shift>0) output = N >> shiftby; else output = N << (-shiftby);
>
> The above is pretty efficient, and once the hotspot compiler gets a hold of
> it, it will be even faster.
>
> There is no assembly operator that shifts based on +/- bits; there are only
> shift-left and shift-right operators. If there was a Java operator/function to
> do what you want, it would still be implemented (in machine language) as:

Doesn't matter, the Java operator *is* defined for negative values.

So the solution to Sanny's problem is:

  output = n >> shiftBy;

-- 
Lew
Honi soit qui mal y pense.
http://upload.wikimedia.org/wikipedia/commons/c/cf/Friz.jpg

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Java left shift and right shift operators. Sanny <softtanks22@hotmail.com> - 2011-04-26 00:38 -0700
  Re: Java left shift and right shift operators. Lothar Kimmeringer <news200709@kimmeringer.de> - 2011-04-26 09:55 +0200
    Re: Java left shift and right shift operators. Patricia Shanahan <pats@acm.org> - 2011-04-26 03:16 -0700
    Re: Java left shift and right shift operators. Lew <noone@lewscanon.com> - 2011-04-26 09:49 -0400
      Re: Java left shift and right shift operators. Travers Naran <tnaran@gmail.com> - 2011-04-26 07:09 -0700
        Re: Java left shift and right shift operators. Lew <noone@lewscanon.com> - 2011-04-26 11:21 -0400
        Re: Java left shift and right shift operators. Martin Gregorie <martin@address-in-sig.invalid> - 2011-04-26 15:37 +0000
      Re: Java left shift and right shift operators. Sanny <softtanks22@hotmail.com> - 2011-04-26 09:32 -0700
        Re: Java left shift and right shift operators. Patricia Shanahan <pats@acm.org> - 2011-04-26 11:09 -0700
          Re: Java left shift and right shift operators. Patricia Shanahan <pats@acm.org> - 2011-04-26 13:09 -0700
        Re: Java left shift and right shift operators. Travers Naran <tnaran@gmail.com> - 2011-04-26 22:40 -0700
          Re: Java left shift and right shift operators. Patricia Shanahan <pats@acm.org> - 2011-04-27 05:34 -0700
            Re: Java left shift and right shift operators. Owen Jacobson <angrybaldguy@gmail.com> - 2011-04-28 00:37 -0400
              Re: Java left shift and right shift operators. Patricia Shanahan <pats@acm.org> - 2011-04-28 16:02 -0700
              Re: Java left shift and right shift operators. Michael Wojcik <mwojcik@newsguy.com> - 2011-04-28 19:22 -0400
          Re: Java left shift and right shift operators. bugbear <bugbear@trim_papermule.co.uk_trim> - 2011-04-27 14:28 +0100
          Re: Java left shift and right shift operators. Thomas Richter <thor@math.tu-berlin.de> - 2011-04-30 00:02 +0200
      Re: Java left shift and right shift operators. Roedy Green <see_website@mindprod.com.invalid> - 2011-04-27 19:25 -0700
        Re: Java left shift and right shift operators. Lew <noone@lewscanon.com> - 2011-04-27 23:08 -0400
  Re: Java left shift and right shift operators. Sanny <softtanks22@hotmail.com> - 2011-04-26 02:04 -0700
    Re: Java left shift and right shift operators. Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-04-26 07:34 -0400
      Re: Java left shift and right shift operators. Lew <noone@lewscanon.com> - 2011-04-26 09:47 -0400
        Re: Java left shift and right shift operators. Patricia Shanahan <pats@acm.org> - 2011-04-27 09:23 -0700
          Re: Java left shift and right shift operators. Lew <noone@lewscanon.com> - 2011-04-27 14:49 -0400
            Re: Java left shift and right shift operators. Paul Cager <paul.cager@googlemail.com> - 2011-04-27 17:28 -0700
              Re: Java left shift and right shift operators. Lew <noone@lewscanon.com> - 2011-04-27 22:06 -0400
      Re: Java left shift and right shift operators. Sanny <softtanks22@hotmail.com> - 2011-04-26 09:39 -0700
        Re: Java left shift and right shift operators. Patricia Shanahan <pats@acm.org> - 2011-04-26 11:17 -0700
        Re: Java left shift and right shift operators. Lew <noone@lewscanon.com> - 2011-04-26 14:55 -0400
          Re: Java left shift and right shift operators. Lew <noone@lewscanon.com> - 2011-04-26 14:57 -0400
          Re: Java left shift and right shift operators. Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2011-04-26 21:38 +0200
          Re: Java left shift and right shift operators. Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-04-26 23:32 +0000
            Re: Java left shift and right shift operators. Lew <noone@lewscanon.com> - 2011-04-27 00:08 -0400
              Re: Java left shift and right shift operators. Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-04-27 06:57 +0000
                Re: Java left shift and right shift operators. Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-04-27 07:00 -0300
                Re: Java left shift and right shift operators. Lew <noone@lewscanon.com> - 2011-04-27 08:42 -0400
                Re: Java left shift and right shift operators. Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-04-27 14:03 +0000
                Re: Java left shift and right shift operators. Lew <noone@lewscanon.com> - 2011-04-27 14:54 -0400
        Re: Java left shift and right shift operators. Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-04-26 21:14 -0400
    Re: Java left shift and right shift operators. Travers Naran <tnaran@gmail.com> - 2011-04-26 07:30 -0700
      Re: Java left shift and right shift operators. Lew <noone@lewscanon.com> - 2011-04-26 11:24 -0400
        Re: Java left shift and right shift operators. Lew <noone@lewscanon.com> - 2011-04-26 11:35 -0400
          Re: Java left shift and right shift operators. Sanny <softtanks22@hotmail.com> - 2011-04-26 09:46 -0700
            Re: Java left shift and right shift operators. Lew <noone@lewscanon.com> - 2011-04-26 15:02 -0400
      Re: Java left shift and right shift operators. Lothar Kimmeringer <news200709@kimmeringer.de> - 2011-04-28 09:14 +0200
  Re: Java left shift and right shift operators. Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-04-26 08:41 -0400
  Re: Java left shift and right shift operators. Robert Klemme <shortcutter@googlemail.com> - 2011-04-26 22:06 +0200

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