[Rd] Very Long Expressions
Prof Brian Ripley
ripley at stats.ox.ac.uk
Mon Jan 24 17:03:55 CET 2005
On Mon, 24 Jan 2005, McGehee, Robert wrote:
[Instructions to the R developers deleted.]
> Secondly, the ?options help (thanks for everyone who reminded me about
> this), says that expressions can have values between 25...100000.
> However, if the original example is set past 4995 on my computers, I
> receive a stack overflow.
More accurately, you caused a protection stack overflow.
>> eval(parse(text = paste(rep(1, 4996), collapse = "+")))
> Error: protect(): stack overflow
> I'm pointing this out not because I will ever approach anywhere near
> this level of nesting, but perhaps that options(expression=5000+) might
> not be meaningful anyway, (unless there are
> processor/compilation-specific ways of getting rid of this stack
> overflow). If so, one might considering lowering the range of valid
> expressions values in the help file.
It's the protect stack you are overflowing, and there are ways to increase
that (look at the command-line flags) and other nested computations that
do not protect repeatedly.
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
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