Date: Fri, 30 Jun 2000 20:15:51 +0200 (MET DST)
From: maechler@stat.math.ethz.ch
To: r-devel@stat.math.ethz.ch
Subject: [Rd] dim(a <- ...) sets invisible flag erronously (PR#587)
CC: R-bugs@biostat.ku.dk
X-Loop: R-bugs@biostat.ku.dk
{Nothing really harmful; R 1.1.0}
dim(.) sets (or doesn't clear) the ``invisible flag'' for printing in
certain circumstances:
> dim(a <- cbind(1)) >
does *not* print as it should :
> dim(a)
[1] 1 1
This is nothing to do with dim: any function will do this.
foo <- function(x) x foo(a <- cbind(1))
It happens because the way invisible is implemented is different in R and S: in S there is a .Auto.print var in frame 1, and in R there is a global variable R_visible, so anything during the evaluation that unsets the flag will ensure that the result is invisible. I don't see how to avoid this without checking the `depth' in the evaluation pretty carefully (and R's semantics differ from those of S in that braced expressions do not generate a frame). Is this worth fixing? print(.Last.value) works all the time, and perhaps you might be persuaded not to write code that uses assignments as arguments?
---
Question to the real "hackers" :
How can I check this using R code alone (not using files),
i.e. (how) can I ask an R expression if its ``invisible flag'' is set or not ?
{help(invisible) doesn't help here}.
Maybe one would want an
is.invisible(.)
function?
There seems to be an unused internal function do_visibleflag in print.c.
Brian D. Ripley, ripley@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 -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-devel 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-devel-request@stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._