GNU bug report logs - #15320
[2.0.7] Rational number representation problem

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Mark H Weaver <mhw <at> netris.org>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#15320: closed ([2.0.7] Rational number representation problem)
Date: Thu, 12 Sep 2013 21:04:03 +0000

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Your message dated Thu, 12 Sep 2013 17:03:34 -0400
with message-id <8738p9n461.fsf <at> tines.lan>
and subject line Re: bug#15320: [2.0.7] Rational number representation problem
has caused the debbugs.gnu.org bug report #15320,
regarding [2.0.7] Rational number representation problem
to be marked as done.

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help-debbugs <at> gnu.org.)


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15320: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=15320
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From: Josh Stokes <jsstokes2 <at> googlemail.com>
To: bug-guile <at> gnu.org
Subject: [2.0.7] Rational number representation problem
Date: Tue, 10 Sep 2013 14:28:37 +0100

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It seems that certain small numbers are represented as integers, as (*
4294967296 4294967296) results in 0, but (* 3294967296 3294967296) returns
the correct value of 10856809481709551616. In addition, (ash 1 64) gives 0,
but (ash 1 65) works correctly.

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From: Mark H Weaver <mhw <at> netris.org>
To: Josh Stokes <jsstokes2 <at> googlemail.com>
Cc: 15320-close <at> debbugs.gnu.org
Subject: Re: bug#15320: [2.0.7] Rational number representation problem
Date: Thu, 12 Sep 2013 17:03:34 -0400

Josh Stokes <jsstokes2 <at> googlemail.com> writes:

> It seems that certain small numbers are represented as integers, as (*
> 4294967296 4294967296) results in 0, but (* 3294967296 3294967296)
> returns the correct value of 10856809481709551616. In addition, (ash 1
> 64) gives 0, but (ash 1 65) works correctly.

This is fixed in Guile 2.0.9.

In case you're curious: this bug came into existence when C compilers
started optimizing out overflow checks, on the theory that if a signed
integer overflow occurs then the behavior is unspecified and thus the
compiler can do whatever it likes.

http://stackoverflow.com/questions/14495636/strange-multiplication-behavior-in-guile-scheme-interpreter/14498437#14498437

    Thanks,
      Mark

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