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*To*: leppie <xacc.ide@x>*Subject*: Re: [Scheme-reports] Strong win later reversed: Real numbers have imaginary part #e0*From*: John Cowan <cowan@x>*Date*: Fri, 21 Dec 2012 11:16:48 -0500*Cc*: scheme-reports <scheme-reports@x>*In-reply-to*: <CAOLEvS0Pa0bYSDBrdkCy5TZkVpx_QvLMLgEFJ=LB+3=+GGTF1g@mail.gmail.com>*References*: <87bodu4r0r.fsf@tines.lan> <20121216041031.GE10312@mercury.ccil.org> <87pq25yh5s.fsf@tines.lan> <20121219221955.GH4477@mercury.ccil.org> <87d2y5y6fb.fsf@tines.lan> <20121221055315.GB28661@mercury.ccil.org> <87y5grsrvm.fsf@tines.lan> <CAOLEvS0hcjUBkwZnYSf6oZhqLSrKChm0Gc4bv_WkWk+XTSO4hQ@mail.gmail.com> <87mwx7smo3.fsf@tines.lan> <CAOLEvS0Pa0bYSDBrdkCy5TZkVpx_QvLMLgEFJ=LB+3=+GGTF1g@mail.gmail.com>

leppie scripsit: > > R6RS and R7RS-draft-8 require that (eqv? +0.0 -0.0) => #f > > R6RS says eqv? should behave like =. Actually not. For one thing, 2.0 and 2 have been different in the sense of `eqv?` ever since R3RS. But what's relevant here is all that blibberty-blibber in the R6RS definition of `eqv?` about being indistinguishable by any finite composition of Scheme's standard arithmetic procedures. In particular, (/ 0.0) is +inf.0, and (/ -0.0) is -inf.0, so they are obviously distinguishable, and `eqv?` must not treat them as the same. As long as your inexact reals are IEEE binaries, you can just distinguish this one case and then fall back to =. -- John Cowan http://www.ccil.org/~cowan <cowan@x> You tollerday donsk? N. You tolkatiff scowegian? Nn. You spigotty anglease? Nnn. You phonio saxo? Nnnn. Clear all so! `Tis a Jute.... (Finnegans Wake 16.5) _______________________________________________ Scheme-reports mailing list Scheme-reports@x http://lists.scheme-reports.org/cgi-bin/mailman/listinfo/scheme-reports

**Follow-Ups**:**Re: [Scheme-reports] Strong win later reversed: Real numbers have imaginary part #e0***From:*Mark H Weaver <mhw@x>

**References**:**Re: [Scheme-reports] Strong win later reversed: Real numbers have imaginary part #e0***From:*Mark H Weaver <mhw@x>

**Re: [Scheme-reports] Strong win later reversed: Real numbers have imaginary part #e0***From:*John Cowan <cowan@x>

**Re: [Scheme-reports] Strong win later reversed: Real numbers have imaginary part #e0***From:*Mark H Weaver <mhw@x>

**Re: [Scheme-reports] Strong win later reversed: Real numbers have imaginary part #e0***From:*John Cowan <cowan@x>

**Re: [Scheme-reports] Strong win later reversed: Real numbers have imaginary part #e0***From:*Mark H Weaver <mhw@x>

**Re: [Scheme-reports] Strong win later reversed: Real numbers have imaginary part #e0***From:*John Cowan <cowan@x>

**Re: [Scheme-reports] Strong win later reversed: Real numbers have imaginary part #e0***From:*Mark H Weaver <mhw@x>

**Re: [Scheme-reports] Strong win later reversed: Real numbers have imaginary part #e0***From:*leppie <xacc.ide@x>

**Re: [Scheme-reports] Strong win later reversed: Real numbers have imaginary part #e0***From:*Mark H Weaver <mhw@x>

**Re: [Scheme-reports] Strong win later reversed: Real numbers have imaginary part #e0***From:*leppie <xacc.ide@x>

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