On Fri, Jun 3, 2011 at 11:51 AM, Sarah Goslee <sarah.gos...@gmail.com> wrote:
> If you don't recognize the official r-project.org R-admin manual as a > legitimate > link then I'm afraid I also can't help you any further since there is nothing > more legitimate than the official documentation. Except the source code! Possible case in point, someone on StackOverflow was wondering why "0 <= x <= 1" isn't a valid expression, neither in the context of what he expected (TRUE if x is between 0 and 1) nor how I explained it would function (as (0<=x) <= 1, and then comparing a TRUE/FALSE against 1) if it were not for the flagging of comparison operators as non-associative in gram.y in the source code. I even recompiled R with <= as left associative to check. Sure enough, I could then type 0 <= 5 <= 1 as a valid expression and get TRUE returned. Now, the user (eventually) understood all of this, but neither he nor I could find this documented in the R docs. Actually, it sems to contradict the code [my **emphasis**]: "The exponentiation operator ‘^’ and the left assignment operators ‘<- - = <<-’ group right to left, **all other operators** group left to right. That is, 2 ^ 2 ^ 3 is 2 ^ 8, not 4 ^ 3, whereas 1 - 1 - 1 is -1, not 1. ". Shortly before that the comparison operators (>, < etc) are listed in a table of precedence with the other operators. Actually I reckon this is a clear documentation bug and I should probably report it... But its lunchtime and there's free cheese... Barry ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.