binary coding of NA, Nan etc.
Prof Brian Ripley wrote:
How would you specify it? You would need a way to specify the bit pattern (of the source or target endianness?) of Inf, -Inf, NA, the class of NaNs (there are many of them) for doubles and perhaps floats too. And R has no type to represent such bit patterns.
I have no real knowledge of binary representation of these 'special' numbers. I was naively thinking a limited set of conventions were used by the majority of the software/libraries. In this context having parameters about endianess and type (as it is already the case for the actual readBin and writeBin) plus the 'convention' (like IEEE-754 may be is). For R things would remain the same, this would just be a choice in encoding NA and friends on output (or input). In my example I saw it as: double: Java_representation (this is always 'big' endianess... a good thing with java binary representation): 0xef7f ffff ffff ffff IEEE-754 0xffwhatever_it_is and so on... float: ...and on... But as you suggested things are (unfortunately) not that simple... I guess for some type, NA and friends might be undefined... I guess what I only have left to do is to wish everybody a good week-end and run home.... Regards, Laurent
I would expect all compiled languages to be using the same representations on modern hardware. However, Java is not in that sense compiled and may well be different: I have no idea. One thing I did not say before: R's standard NA is the NaN with low word of 1954. I have no idea how to generate that on another system except via the sort of sneaky tricks arithmetic.c plays. The multiplicity of NaNs complicates this enormously. -- Brian D. Ripley, ripley at stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272860 (secr) Oxford OX1 3TG, UK Fax: +44 1865 272595
Laurent Gautier CBS, Building 208, DTU PhD. Student D-2800 Lyngby,Denmark tel: +45 45 25 24 85 http://www.cbs.dtu.dk/laurent -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._