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*To*: Paul Schlie <schlie@xxxxxxxxxxx>*Subject*: Re: Error objects in general*From*: Alan Watson <a.watson@xxxxxxxxxxxxxxxx>*Date*: Sun, 30 Oct 2005 05:17:21 -0800*Cc*: bear <bear@xxxxxxxxx>, srfi-77@xxxxxxxxxxxxxxxxx*Delivered-to*: srfi-77@xxxxxxxxxxxxxxxxx*In-reply-to*: <BF8A2918.BF49%schlie@xxxxxxxxxxx>*Organization*: Centro de Radioastronomía y Astrofísica UNAM*References*: <BF8A2918.BF49%schlie@xxxxxxxxxxx>*User-agent*: Mozilla Thunderbird 1.0 (X11/20050317)

Paul Schlie wrote:

- Should there be an observable difference between assoc failing to find a match given operands with well defined values, vs. given operands having un-specified values?

- Should a comparison operation (= 0 X) return #t #f or something else if the value of X is an unspecified NaN value? [as such a value may or may not be 0]?

Section 5.7 of IEEE 754 says #f.

- what should (list-ref x y) return if y had an un-specified value?

NaNs are inexact, so this should signal an error as y must be exact.

- or more generally, what value should (car #t) or (if #f #f) return?

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

**References**:**Re: Error objects in general***From:*Paul Schlie

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