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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*: Wed, 19 Dec 2012 17:19:55 -0500*Cc*: scheme-reports <scheme-reports@x>*In-reply-to*: <87pq25yh5s.fsf@tines.lan>*References*: <20121214223854.GX29857@mercury.ccil.org> <CAGUt3y55KEVFn=6_i9yRXR8w_e8Nk2tN7QGCF8rEhYTs2Xgrjw@mail.gmail.com> <878v8z5iq8.fsf@tines.lan> <874njn5b65.fsf@tines.lan> <20121215204015.GG13463@mercury.ccil.org> <87obhv3ts0.fsf@tines.lan> <20121215231548.GC10312@mercury.ccil.org> <87bodu4r0r.fsf@tines.lan> <20121216041031.GE10312@mercury.ccil.org> <87pq25yh5s.fsf@tines.lan>

Mark H Weaver scripsit: > My point is that your ComplexRepresentation page states that Guile and > Racket do not support complex numbers of mixed exactness, but that's not > quite true. There is one important special case of mixed exactness that > *is* supported in Guile, Racket, Ikarus, and perhaps others. In that case, *every* Scheme that supports inexact reals at all, a priori supports complex numbers of mixed exactness such that the imag-part is 0. This is true a priori, and so doesn't belong on the ImplementationContrast pages, which are about empirical differences between Schemes. Or is what you mean that some Schemes, when asked for the imag-part of 2.0, may return 0.0 rather than 0? I can check for that possibility when I'm back home. > Another test that would be worthwhile is this: > > (list (eqv? +0.0 -0.0) > (eqv? (make-rectangular +0.0 1.0) > (make-rectangular -0.0 1.0)) > (eqv? (make-rectangular 1.0 +0.0) > (make-rectangular 1.0 -0.0)) > > I wouldn't be surprised if some Schemes distinguish signed zeroes in the > real part but not in the imaginary part. If an implementation discards > inexact zero imaginary parts, then it probably discards the sign as well > as the exactness. I'll try that. -- Dream projects long deferred John Cowan <cowan@x> usually bite the wax tadpole. http://www.ccil.org/~cowan --James Lileks _______________________________________________ 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>

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

**References**:**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:*Sascha Ziemann <ceving@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:*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>

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