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> From: William D Clinger <will@xxxxxxxxxxx>> >> Paul Schlie wrote: >> Any possibility of considering a somewhat more numerically >> consistent abstract notation for ambiguously signed values? >> >> (i.e. ~nan.0 replaces the positively signed +nan.0 notation) >> >> Thereby enabling the optionally supported designations: >> >> ~inf.0 ~inf.0 >> -inf.0 -0.0 0 +0.0 +inf.0 >> <|------------------------|-----------------------|> >> <--------- -nan.0 -------> <-------- +nan.0 -------> >> <---------------------- ~nan.0 --------------------> > > This is an interesting question. The IEEE-754 standard > does not mandate *any* means for determining the sign of > a NaN, but recommends a CopySign function that could be > used for that purpose. >> ... > SRFI 77 does not require all NaNs to print as +nan.0. > In fact, I don't believe SRFI 77 forbids any of the > NaNs you wrote above to print as ~nan.0. In that > sense, I believe SRFI 77 already allows the extension > you desire. > > The extension you desire should not be mandated, > however, because the IEEE standards explicitly allow > a very large variety of encodings for the NaN values > they specify. > > Will I agree that they need not be mandated, however the designation of +nan.0 as the default NaN notation would seem to imply a positive numerical ambiguity; thereby suspect if R6RS formalized '~' as being a formally accepted notation for numerical sign ambiguity, then ~nan.0 could be formally specified as the notation for a generally ambiguous value; from which other somewhat more precise ambiguities may then be utilized as a compatible extension? -paul-