Warnings generated by log2()/log10() are really large/takes a long time to display

On Wed, Feb 27, 2008 at 12:56 AM, Prof Brian Ripley
On Wed, 27 Feb 2008, Martin Maechler wrote:

 > Thank you Henrik,
 >
 >>>>>> "HenrikB" == Henrik Bengtsson <hb at stat.berkeley.edu>
 >>>>>>     on Tue, 26 Feb 2008 22:03:24 -0800 writes:
 >
 > {with many superfluous empty statements ( i.e., trailing ";" ):
 Indeed!
I like to add a personal touch to the code I'm writing ;)

Seriously, I added them here as a bait in order to get a chance to say
that I finally found a good reason for adding the semicolons.  If you
cut'n'paste code from certain web pages it may happen that
newlines/carriage returns are not transferred and all code is pasted
into the same line at the R prompt.  With semicolons you still get a
valid syntax.  I cannot remember under what conditions this happened -
if it was for certain web browser, web page/blog, online page editor,
OS and so, but I'm quite sure it was while I've put online code
examples for my latest project.  Maybe someoneelse also has noticed
this?

 >    HenrikB> x <- rnorm(1e6);
 >
 >    [................]
 >
 >
 >    HenrikB> y <- log2(x);  # or log10(x)
 >    HenrikB> w <- warnings();
 >    HenrikB> print(object.size(w));
 >    HenrikB> ## [1] 8000536
 >    HenrikB> str(w);
 >    HenrikB> ## List of 1
 >    HenrikB> ##  $ NaNs produced: language log(c(2.12082478659910,
 >    HenrikB> 1.40263187453398, 1.574125429
 >    HenrikB> ## 83486, -0.816399069824751,  0.215940065840533, 1.20975177084379,
 >    HenrikB> -0.340287874362
 >    HenrikB> ## 813, 0.117151537611550,  ...
 >    HenrikB> ##  - attr(*, "dots")= list()
 >    HenrikB> ##  - attr(*, "class")= chr "warnings"
 >
 >    HenrikB> Note also how long it takes to display and str() the warning.
 >
 > Yes, indeed.
 > It's a subtle problem and happens
 > because in do_log1arg() a new call is constructed in which 'x'
 > has already been evaluated.
 >
 > A subtle fix to the subtle problem
 > is to replace  CAR(args) by CADR(call) in there
 >
 > --- arithmetic.c      (Revision 44626)
 > +++ arithmetic.c      (working copy)
 > @@ -1372,7 +1372,9 @@
 >     if(PRIMVAL(op) == 10) tmp = ScalarReal(10.0);
 >     if(PRIMVAL(op) == 2)  tmp = ScalarReal(2.0);
 >
 > -    PROTECT(Call = lang3(install("log"), CAR(args), tmp));
 > +    /* CADR(call) instead of CAR(args), since 'args' have been
 > +     * evaluated in Dispatch*(..) above : */
 > +    PROTECT(Call = lang3(install("log"), CADR(call), tmp));
 >     res = eval(Call, env);
 >     UNPROTECT(1);
 >     return res;
 >
 > -----
 >
 > That does fix the problem you've reported (and passes "make check")
 > but I'm not quite at ease with it, since it will lead to
 > effectively evaluate the argument *twice*.
 >
 > A different approach that I'd find cleaner
 > would be to *not* construct and eval() a
 > new Call inside do_log1arg, but I assume there had been a good
 > reason for doing things they way they are now...
 There was (although possibly no longer -- there was a bug in S4 dispatch
 of primitives that failed to re-promise args).

 The real issue is somewhere else entirely, the complete deparse in
 print.warnings.
Thank you both for looking into this.

Henrik

 >
 > Martin Maechler, ETH Zurich
 >
 > ______________________________________________
 > R-devel at r-project.org mailing list
 > https://stat.ethz.ch/mailman/listinfo/r-devel
 >
 --
 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 272866 (PA)
 Oxford OX1 3TG, UK                Fax:  +44 1865 272595

Warnings generated by log2()/log10() are really large/takes a long time to display

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