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*To*: Aubrey Jaffer <agj@xxxxxxxxxxxx>*Subject*: Re: reading NaNs*From*: Alan Watson <a.watson@xxxxxxxxxxxxxxxx>*Date*: Tue, 25 Oct 2005 18:13:54 -0500*Cc*: tb@xxxxxxxxxx, srfi-77@xxxxxxxxxxxxxxxxx*Delivered-to*: srfi-77@xxxxxxxxxxxxxxxxx*In-reply-to*: <20051025224529.2760C1B77BB@xxxxxxxxxxxxxxxxxxxxx>*Organization*: Centro de Radioastronomía y Astrofísica UNAM*References*: <20051021145326.816C11B77BB@xxxxxxxxxxxxxxxxxxxxx> <20051022011713.1F22A1B77BB@xxxxxxxxxxxxxxxxxxxxx> <87vezqmjkq.fsf@xxxxxxxxxxxxxxxxx> <20051022232548.5A2971B77BB@xxxxxxxxxxxxxxxxxxxxx> <873bmtxdnm.fsf@xxxxxxxxxxxxxxxxx> <20051023181854.4E7DD1B77BB@xxxxxxxxxxxxxxxxxxxxx> <871x2cowe8.fsf@xxxxxxxxxxxxxxxxx> <20051023195403.A50AF1B77BB@xxxxxxxxxxxxxxxxxxxxx> <435BEC21.60509@xxxxxxxxxxxx> <20051023205012.BFD241B77BB@xxxxxxxxxxxxxxxxxxxxx> <87zmoz27dg.fsf@xxxxxxxxxxxxx> <87hdb7kgmk.fsf@xxxxxxxxxxxxxxxxx> <87k6g3zw34.fsf@xxxxxxxxxxxxx> <871x2bkfj7.fsf@xxxxxxxxxxxxxxxxx> <8764rnu45b.fsf@xxxxxxxxxxxxx> <87br1fiv26.fsf@xxxxxxxxxxxxxxxxx> <87ll0jpu0q.fsf@xxxxxxxxxxxxx> <20051024022744.6CA581B77BB@xxxxxxxxxxxxxxxxxxxxx> <87veznbb37.fsf@xxxxxxxxxxxxx> <8764rnbaqr.fsf@xxxxxxxxxxxxxxxxx> <435C9A65.7060106@xxxxxxxxxxxxxxxx> <20051024153539.D98031B77BB@xxxxxxxxxxxxxxxxxxxxx> <435D49E3.2010001 @astrosmo.unam.mx> <20051025224529.2760C1B77BB@xxxxxxxxxxxxxxxxxxxxx>*User-agent*: Mozilla Thunderbird 1.0 (X11/20050317)

Aubrey Jaffer wrote:

Having a universal read/write representation for arbitrary bit patterms prevents including information like the procedure causing the NaN in its printed representation.

I don't see this. Can you elaborate?

| However, I still think we need a read syntax. Suppose program A | calculates a value and writes it to a file and program B reads the | value from the file and uses it. Is is not useful for program A to | be able to communicate to program B that it got a NaN? [...] If program A writes out its state, it would be useful to see that NaNs were computed. It gives operators a chance to capture the use case which provoked the error. If the program state is very valuable, then it can be repaired manually. But if program B reads its initial state from the file, its reading of NaNs puts errors into its state which can propagate and corrupt it.

Um, how about program B doing: (let ((x (read))) (if (nan? x) (display "Help! Help! Program A is feeding me NaNs!")))

Regards, Alan -- Dr Alan Watson Centro de Radioastronomía y Astrofísica Universidad Astronómico Nacional de México

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**reading NaNs***From:*Aubrey Jaffer

**Re: reading NaNs***From:*Aubrey Jaffer

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