On 02/24/2011 11:20 AM, Prof Brian Ripley wrote:
On Thu, 24 Feb 2011, Tal Galili wrote:
Thank you all for the answers.
So if I may extend on the question -
When is it important to use 'Literal integer'?
Under what situations could not using it cause problems?
Is it a matter of efficiency or precision or both?
Efficiency: it avoids unnecessary type conversions. For example
length(x) > 1
has to coerce the lhs to double. We have converted the base code to use integer
constants because such small efficiency gains can add up.
Integer vectors can be stored more compactly than doubles, but that is not going
to help for length 1:
object.size(1)
48 bytes
object.size(1L)
48 bytes
(32-bit system).
see:
n <- 0L : 100L
szi <- sapply (n, function (n) object.size (integer (n)))
szd <- sapply (n, function (n) object.size (double (n)))
plot (n, szd)
points (n, szi, col = "red")
Thanks,
Tal
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On Wed, Feb 23, 2011 at 6:15 PM, Tsjerk Wassenaar <tsje...@gmail.com> wrote:
Hi Gene,
It means 'Literal integer'.
So 1L is a proper integer 1, and 0L is a proper integer 0.
Hope it helps,
Tsjerk
On Wed, Feb 23, 2011 at 5:08 PM, Gene Leynes <gleyne...@gmail.com> wrote:
I've been wondering what L means in the R computing context, and was
wondering if someone could point me to a reference where I could read
about
it, or tell me what it's called so that I can search for it myself. (L
by
itself is a little too general for a search term).
I encounter it in strange places, most recently in the "save"
documentation.
save(..., list = character(0L),
file = stop("'file' must be specified"),
ascii = FALSE, version = NULL, envir = parent.frame(),
compress = !ascii, compression_level,
eval.promises = TRUE, precheck = TRUE)
I remember that you can also find it when you step inside an apply
function:
sapply(1:10, function(x)browser())
Called from: FUN(1:10[[1L]], ...)
I apologize for being vague, it's just something that I would like to
understand about the R language (the R word).
Thank you!
Gene
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--
Tsjerk A. Wassenaar, Ph.D.
post-doctoral researcher
Molecular Dynamics Group
* Groningen Institute for Biomolecular Research and Biotechnology
* Zernike Institute for Advanced Materials
University of Groningen
The Netherlands
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--
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Dipartimento dei Materiali e delle Risorse Naturali
Università degli Studi di Trieste
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