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*To*: jcowan@xxxxxxxxxxxxxxxxx*Subject*: +nan.0 problems*From*: Aubrey Jaffer <agj@xxxxxxxxxxxx>*Date*: Sat, 22 Oct 2005 12:30:37 -0400 (EDT)*Cc*: bear@xxxxxxxxx, srfi-77@xxxxxxxxxxxxxxxxx*Delivered-to*: srfi-77@xxxxxxxxxxxxxxxxx*In-reply-to*: <20051022020312.GB5632@NYCMJCOWA2> (jcowan@xxxxxxxxxxxxxxxxx)*References*: <20051021145326.816C11B77BB@xxxxxxxxxxxxxxxxxxxxx> <20051021155906.GC16464@NYCMJCOWA2> <Pine.LNX.4.58.0510210910130.18969@xxxxxxxxxxxxxx> <20051022020312.GB5632@NYCMJCOWA2>

| Date: Fri, 21 Oct 2005 22:03:12 -0400 | From: "John.Cowan" <jcowan@xxxxxxxxxxxxxxxxx> | | bear scripsit: | | > >> Being error objects, syntax for NaNs should be unspecified. | > | > >I don't see how that follows. | > | > He means that NaNs should arise from error operations, not from | > the normal functioning of the reader. If (read) returns an error | > object, it should mean that (read) encountered an error. | | Since NaN is part of the prescribed behavior of IEEE floats, it is | not an error object in that sense; in particular there are | operations defined on NaN that do not produce NaN, notably the | relational ones. The total order of the reals is a crucial property for many applications. Any subset of the reals has a total order. The reals with +inf.0 and -inf.0 have a total order. But the reals with +inf.0, -inf.0, and +nan.0 do not have a total order [because (<= 5 +nan.0) and (>= 5 +nan.0) would both be false]. SRFI-77 states: This SRFI regards +nan.0 as a real number whose value is so indeterminate that it might represent any real number within the closed interval [-inf.0,+inf.0]. +nan.0 being real conflicts with the total order of the real numbers. This could be resolved by either: (real? +nan.0) ==> #f and (complex? +nan.0) ==> #f or Stop using the term `real' to refer to IEEE flonums. How about RIEEEL? -=-=-=-=- The line: (real? +nan.0) ==> #t occurs twice in the "Numerical Type Predicates" section. -=-=-=-=- There is one occurrence of -nan.0 in SRFI-77: Furthermore inf.0, +inf.0, -inf.0, nan.0, +nan.0, and -nan.0 are external representations for flonums.

**Follow-Ups**:**Re: +nan.0 problems***From:*Marcin 'Qrczak' Kowalczyk

**Re: +nan.0 problems***From:*John.Cowan

**References**:**arithmetic issues***From:*Aubrey Jaffer

**Re: arithmetic issues***From:*John.Cowan

**Re: arithmetic issues***From:*bear

**Re: arithmetic issues***From:*John.Cowan

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