[Rcpp-devel] short, unsigned short, long, unsigned long, long double
Romain Francois
romain at r-enthusiasts.com
Tue Apr 6 14:27:34 CEST 2010
Le 06/04/10 14:24, Douglas Bates a écrit :
> On Tue, Apr 6, 2010 at 7:15 AM, Douglas Bates<bates at stat.wisc.edu> wrote:
>> On Tue, Apr 6, 2010 at 6:54 AM, Romain Francois
>> <romain at r-enthusiasts.com> wrote:
>>> Hello,
>>>
>>> I have added support for these primitive types in Rcpp, so that one can
>>> wrap containers such as :
>>>
>>> std::vector<short>, ...
>>>
>>> Is this something that should be protected in case there is no "short",
>>> "long", etc ?
>>
>> You can check in R's .Machine object on the various sizes for which R
>> scans. It can tell you if there is a difference between long and long
>> long or between double and long double. It does not list anything
>> regarding short. The sum of double.digits and double.exponent is the
>> number of bits in a double. Generally log(.Machine$integer.max, 2) is
>> 1 less than the number of bits in an int.
>>
>>
>>> str(.Machine)
>> List of 18
>> $ double.eps : num 2.22e-16
>> $ double.neg.eps : num 1.11e-16
>> $ double.xmin : num 2.23e-308
>> $ double.xmax : num 1.80e+308
>> $ double.base : int 2
>> $ double.digits : int 53
>> $ double.rounding : int 5
>> $ double.guard : int 0
>> $ double.ulp.digits : int -52
>> $ double.neg.ulp.digits: int -53
>> $ double.exponent : int 11
>> $ double.min.exp : int -1022
>> $ double.max.exp : int 1024
>> $ integer.max : int 2147483647
>> $ sizeof.long : int 4
>> $ sizeof.longlong : int 8
>> $ sizeof.longdouble : int 12
>> $ sizeof.pointer : int 4
>>> log(.Machine$integer.max, 2)
>> [1] 31
>
> Perhaps I am not answering the question that you asked - that sort of
> thing happens when answering email while still on the first cup of
> coffee. More helpful might be the comments in the limits include file
> for libstdc++ on Debian/Ubuntu
>
> // The numeric_limits<> traits document implementation-defined aspects
> // of fundamental arithmetic data types (integers and floating points).
> // From Standard C++ point of view, there are 13 such types:
> // * integers
> // bool (1)
> // char, signed char, unsigned char (3)
> // short, unsigned short (2)
> // int, unsigned (2)
> // long, unsigned long (2)
> //
> // * floating points
> // float (1)
> // double (1)
> // long double (1)
> //
> // GNU C++ understands (where supported by the host C-library)
> // * integer
> // long long, unsigned long long (2)
> //
> // which brings us to 15 fundamental arithmetic data types in GNU C++.
>
> So it looks like short is part of standard C++ but not long long.
Even better, thanks again.
BTW, I am also a recurrent victim of the "before the first cup of
coffee" pattern.
Romain
--
Romain Francois
Professional R Enthusiast
+33(0) 6 28 91 30 30
http://romainfrancois.blog.free.fr
|- http://bit.ly/9aKDM9 : embed images in Rd documents
|- http://tr.im/OIXN : raster images and RImageJ
|- http://tr.im/OcQe : Rcpp 0.7.7
More information about the Rcpp-devel
mailing list