[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

*To*: Aubrey Jaffer <agj@x>*Subject*: Re: [Scheme-reports] Numerical example (real? -2.5+0.0i)*From*: John Cowan <cowan@x>*Date*: Tue, 16 Aug 2011 14:25:11 -0400*Cc*: scheme-reports@x*In-reply-to*: <20110816172825.413A48C0521@voluntocracy.org>*References*: <qotei0nf78i.fsf@ruuvi.it.helsinki.fi> <20110815160512.1C1008C0663@voluntocracy.org> <20110815190618.GB31780@mercury.ccil.org> <20110816172825.413A48C0521@voluntocracy.org>

Aubrey Jaffer scripsit: > Algebraically, the complex numbers are the field of reals extended by > a solution of x^2+1=0. All reals are complex; there is no difference > between real 2.0 and 2.0+0.0i. I used the term "general complex number" in the same sense it is used in R5RS, to mean a number whose imaginary part is nonzero. > FreeSnell <http://people.csail.mit.edu/jaffer/FreeSnell> is a Scheme > application for computing the optical properties of thin-films. It > uses complex numbers intensively in its computations. The only > effects of distinguishing real real from complex real numbers would be > to increase its storage and reduce its performance. I don't understand this. How can either storage or performance depend on the result returned by the real? procedure? > So no, SCM won't be distinguishing "real reals" from "complex reals". > > | The rationale here is that a number with imaginary part 0.0 isn't > | necessarily on the real line, since 0.0 just means a number x such > | that 0 < x < the smallest representable inexact number. > > Is that the official r7rs model of inexact numbers? Nothing about rationales is official, and this one isn't even in the report, so that question is self-answering. > It isn't SCM's model; <http://srfi.schemers.org/srfi-70/srfi-70.html> > is. SRFI-70 specifies the result of numerical procedures applied to > infinities and zeros. There will eventually be a specification in R7RS-small as well, probably similar to R5RS and IEEE 754:2008. > I don't see this information in r7rs-draft-3.pdf, leaving a huge hole > in the specification. I agree. It would be helpful to provide suitable text. -- Verbogeny is one of the pleasurettes John Cowan <cowan@x> of a creatific thinkerizer. http://www.ccil.org/~cowan --Peter da Silva _______________________________________________ Scheme-reports mailing list Scheme-reports@x http://lists.scheme-reports.org/cgi-bin/mailman/listinfo/scheme-reports

**Follow-Ups**:**Re: [Scheme-reports] Numerical example (real? -2.5+0.0i)***From:*Andre van Tonder <andre@x>

**Re: [Scheme-reports] Numerical example (real? -2.5+0.0i)***From:*Aubrey Jaffer <agj@x>

**References**:**[Scheme-reports] Numerical example (real? -2.5+0.0i)***From:*Jussi Piitulainen <jpiitula@x>

**Re: [Scheme-reports] Numerical example (real? -2.5+0.0i)***From:*Aubrey Jaffer <agj@x>

**Re: [Scheme-reports] Numerical example (real? -2.5+0.0i)***From:*John Cowan <cowan@x>

**Re: [Scheme-reports] Numerical example (real? -2.5+0.0i)***From:*Aubrey Jaffer <agj@x>

- Prev by Date:
**Re: [Scheme-reports] diff between R6RS and the R7RS small language draft** - Next by Date:
**Re: [Scheme-reports] Padding/placeholders (hashes) in numerical syntax** - Previous by thread:
**Re: [Scheme-reports] Numerical example (real? -2.5+0.0i)** - Next by thread:
**Re: [Scheme-reports] Numerical example (real? -2.5+0.0i)** - Index(es):