Correct, my message has nothing to do with the initial problem. Jos > -----Original Message----- > From: Dmitry Pavlov [mailto:dpav...@ipa.nw.ru] > Sent: miércoles, 08 de mayo de 2013 12:11 > To: Jos Koot > Cc: users@racket-lang.org > Subject: Re: [racket] ~r: formatting 0.0 with 'exponential > and #:precision > > Hi Jos, > > I have nothing sensible to say about line 340 and > the fix you propose (probably it is right), but the > initial problem with 0.0 originates not in line 340 > but rather in lines 330-331 > > (if (zero? N-abs) > (values 0 0 (if exactly? significand-precision 0)) > > or line 311 > > [exponent (- significand-precision e-adjust) > > When we do (~r 0.0 #:notation 'exponential #:precision 4), > significand-precision is equal to 4 and e-adjust happens > to be zero. > > > Regards, > > Dmitry > > > > On 05/08/2013 11:21 AM, Jos Koot wrote: > > I came across another thing: > > > > #lang racket > > > > (define x #e100.e-50000) > > (rational? x) ; #t > > (log x) ; -inf.0 > > (exact->inexact x); 0.0 > > (~r x #:notation 'exponential) ; error inexact->exact: no exact > > representation > > number: -inf.0 > > > > I think this is introduced in line 340 of racket/format.rkt > which contains: > > (inexact->exact (floor (/ (log N-abs) (log base)))) > > for the first estimate of the order of magnitude. > > > > As the docs of ~r say "The exactness or inexactness of x > does not affect its > > formatting.", this behaviour may well be intentional. > > > > It is possible though to avoid the error by subtracting the > log of the > > denominator from that of the nominator after conversion to > exact rational. > > Proc order-of-magnitude (in math I think) does this, but is > for base 10 > > only. May be I should adapt order-of-magnitude such as to > accept a base > > argument? > > > > Best wishes, Jos > > > >> -----Original Message----- > >> From: users-boun...@racket-lang.org > >> [mailto:users-boun...@racket-lang.org] On Behalf Of Dmitry Pavlov > >> Sent: martes, 07 de mayo de 2013 19:12 > >> To: users@racket-lang.org > >> Subject: [racket] ~r: formatting 0.0 with 'exponential and > #:precision > >> > >> Hello, > >> > >> I just came across the following oddness with formatting > >> of real numbers: > >> > >> > (~r 1.0 #:notation 'exponential #:precision '(= 4)) > >> "1.0000e+00" > >> > >> OK > >> > >> > >> > (~r 0.0 #:notation 'exponential #:precision '(= 4)) > >> "0.e+04" > >> > >> ??? > >> > >> Is there a rational explanation of why did > >> the requested precision go into the exponent > >> number for 0.0? > >> > >> Thanks. > >> > >> > >> Best regards, > >> > >> Dmitry > >> ____________________ > >> Racket Users list: > >> http://lists.racket-lang.org/users > > > > > > >
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