From: "Mattias Engdegård" <mattiase@acm.org>
To: David Ongaro <david.ongaro@hamburg.de>
Cc: 41279-done@debbugs.gnu.org
Subject: bug#41279: 26.3; Calc: sum(gcd(0,n),n,-1,-1) evaluates to -1
Date: Fri, 15 May 2020 20:21:47 +0200 [thread overview]
Message-ID: <6029B2F2-E131-46D8-A32A-57B158477DEA@acm.org> (raw)
In-Reply-To: <20621430-4DFE-4E40-A616-9D404DDBB2BF@hamburg.de>
15 maj 2020 kl. 19.44 skrev David Ongaro <david.ongaro@hamburg.de>:
> I see, so the simplest reproduction of the bug doesn't involve the sum, but just the evaluation of gcd(0, x) or gcd(x, 0). Your fix seems sensible to me, I don't see why you consider it a 'hack'. The simplification gcd(0, x)=gcd(x, 0)=abs(x) seems legit and matches the gcd definition "The largest positive integer that divides each of the integers".
Quite, but there is a small possibility that further simplification relies on the gcd(0,x)=x behaviour. You never know with Calc: it is complex and everything seems interconnected. After all, abs is often an obstacle in algebraic transforms; you often end up splitting cases.
That said, it's probably the right thing to do. Now pushed to master, which means that you need to build a development snapshot from source, or apply the change (60cd6cce55) to your Emacs.
prev parent reply other threads:[~2020-05-15 18:21 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-15 4:52 bug#41279: 26.3; Calc: sum(gcd(0,n),n,-1,-1) evaluates to -1 David Ongaro
2020-05-15 10:19 ` Mattias Engdegård
2020-05-15 17:44 ` David Ongaro
2020-05-15 18:21 ` Mattias Engdegård [this message]
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