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Re: Comparing Arbitrary-Precision Integers

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"David T. Ashley" <dashley@gmail.com> wrote in message
news:sj8318pmtqrjdlotfttuqji8mqndf8odms@4ax.com...
> Hi,
>
> I'm using a 2's complement machine (and I'm comfortable baking this
> assumption into the code).  I've implemented a large number of
> functions on signed integers that are longer than the machine
> supports.
>
> Does the code below for comparison look correct?
>
> I think the right approach is to compare the most significant limb in
> a signed sense then to compare the least significant limbs in an
> unsigned sense.  Is that right?

Does your code  work? Test with a reasonable mix of positive and negative
numbers (some of which must be equal in the most significant words) to see
if it gives the expected results.

However I might just subtract one number from the other; the sign of the
result will tell you if the relation is < or >=. But you need to check for
all words zero to distinguish > and =.

That assumes you have a reasonably efficient subtract function. (Having 
dedicated functions to check each of =,!=,<,<=,>=,>, when a specific
comparison is in mind, might also help to streamline things. Equals/not 
equals are particularly easy.)

-- 
Bartc 

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Comparing Arbitrary-Precision Integers David T. Ashley <dashley@gmail.com> - 2012-07-26 16:06 -0400
  Re: Comparing Arbitrary-Precision Integers Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-07-26 17:01 -0400
    Re: Comparing Arbitrary-Precision Integers Tim Rentsch <txr@alumni.caltech.edu> - 2012-09-07 11:49 -0700
  Re: Comparing Arbitrary-Precision Integers "BartC" <bc@freeuk.com> - 2012-07-26 22:20 +0100
    Re: Comparing Arbitrary-Precision Integers Ike Naar <ike@sverige.freeshell.org> - 2012-07-26 21:46 +0000
      Re: Comparing Arbitrary-Precision Integers "BartC" <bc@freeuk.com> - 2012-07-26 23:14 +0100
        Re: Comparing Arbitrary-Precision Integers David T. Ashley <dashley@gmail.com> - 2012-07-27 17:55 -0400
  Re: Comparing Arbitrary-Precision Integers Michael Angelo Ravera <maravera@prodigy.net> - 2012-07-26 17:51 -0700
  Re: Comparing Arbitrary-Precision Integers bartek szurgot <basz@no.spam> - 2012-07-27 08:53 +0200
    Re: Comparing Arbitrary-Precision Integers David T. Ashley <dashley@gmail.com> - 2012-07-27 18:02 -0400
      Re: Comparing Arbitrary-Precision Integers Ike Naar <ike@iceland.freeshell.org> - 2012-07-27 22:23 +0000
        Re: Comparing Arbitrary-Precision Integers Keith Thompson <kst-u@mib.org> - 2012-07-27 16:53 -0700
          Re: Comparing Arbitrary-Precision Integers David T. Ashley <dashley@gmail.com> - 2012-07-27 21:25 -0400
      Re: Comparing Arbitrary-Precision Integers Noob <root@127.0.0.1> - 2012-07-30 14:29 +0200
        Re: Comparing Arbitrary-Precision Integers David T. Ashley <dashley@gmail.com> - 2012-07-30 09:28 -0400
  Re: Comparing Arbitrary-Precision Integers "io_x" <a@b.c.invalid> - 2012-07-27 20:46 +0200

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