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

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Message #10 received at 15320-close <at> debbugs.gnu.org (full text, mbox):

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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