Path: csiph.com!eternal-september.org!feeder.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Paul Rubin Newsgroups: comp.lang.forth Subject: Re: fatan2 2012 Date: Fri, 02 Sep 2016 12:02:51 -0700 Organization: A noiseless patient Spider Lines: 13 Message-ID: <87poomnmzo.fsf@jester.gateway.pace.com> References: <2016Aug22.120058@mips.complang.tuwien.ac.at> <2016Aug23.131107@mips.complang.tuwien.ac.at> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: mx02.eternal-september.org; posting-host="7bfc8f5b1c0c0e2e29d3a5c3abe51644"; logging-data="22623"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+XqftMafcsj43olxacB+Ux" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) Cancel-Lock: sha1:K/VofjvVXIncPUJ2c7jOjJxefOc= sha1:yZH1NSk+WkK8VPCH6gNW1hy2AjI= Xref: csiph.com comp.lang.forth:50627 albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) writes: >>|If y is +/-0 and x is < 0, +/-pi shall be returned. >>(plus other specific cases). I think that the order of the +/- is >>significant, but am too lazy to look it up. > It looks like a bug-compatibility with a stone-age mainframe. > Furthermore it cannot be fullfilled because pi has no > representation in the fp set of computers (!). It looks more like a specification of the right thing to do with the signs, than one saying pi's representation must be exact. And it's probably inspired by IEEE754 or something similar, which put some effort into getting branch cuts consistent. Old mainframes often got that wrong.