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*To*: Mark H Weaver <mhw@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 14:57:51 -0500*Cc*: scheme-reports <scheme-reports@x>*In-reply-to*: <878v8rrywr.fsf@tines.lan>*References*: <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> <20121221161648.GB6196@mercury.ccil.org> <878v8rrywr.fsf@tines.lan>

Mark H Weaver scripsit: > > Actually not. For one thing, 2.0 and 2 have been different in > > the sense of `eqv?` ever since R3RS. > > Since R2RS actually, if one pays attention to "will return #!false" > language in the first sentences of the definition [of `eq?`] instead > of the "Generally speaking ... should be used" language near the bottom. What speaks loudest to me is "The rules for identity of numbers are extremely implementation-dependent and should not be relied on." The definition of `eqv?` overrides this for exact numbers, but leaves it alone for inexact numbers. So their equivalence under `eqv?` is simply not defined by R2RS. In any case, the last surviving R3RS implementation available to me is Oaklisp, and it doesn't care much about conformance. > > As long as your inexact reals are IEEE binaries, you can just > > distinguish this one case and then fall back to =. > > Not quite. One must handle cases such as (eqv? 1+0.0i 1-0.0i) => #f. I was speaking only of real numbers, and certainly only a single precision. With only two Schemes supporting multiple precisions (Racket and NexJ), and with the question of contagion unspecified, it's a borderline issue. -- Said Agatha Christie / To E. Philips Oppenheim John Cowan "Who is this Hemingway? / Who is this Proust? cowan@x Who is this Vladimir / Whatchamacallum, http://www.ccil.org/~cowan This neopostrealist / Rabble?" she groused. --George Starbuck, Pith and Vinegar _______________________________________________ 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:*Per Bothner <per@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:*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>

**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>

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