Let me add the following to the discussion of identical(0, -0). I would like to suggest to replace the paragraph
'identical' sees 'NaN' as different from 'NA_real_', but all 'NaN's are equal (and all 'NA' of the same type are equal). in ?identical by the following text, which is a correction of my previous suggestion for the same paragraph Components of numerical objects are compared as follows. For non-missing values, "==" is used. In particular, '0' and '-0' are considered equal. All 'NA's of the same type are equal and all 'NaN's are equal, although their bit patterns may differ in some cases. 'NA' and 'NaN' are always different. Note also that 1/0 and 1/(-0) are different. The suggestion for the default of identical(0, -0) is TRUE, because the negative zero is much less important than NA na NaN and, possibly, distinguishing 0 and -0 could even be deprecated. Moreover, the argument of efficiency of memcmp cannot be used here, since there are different variants of NaN and NA, which should not be distinguished by default. Petr. ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
