[Rd] long integer in R?
Simon Urbanek
simon.urbanek at r-project.org
Sun Feb 14 00:24:19 CET 2010
On Feb 13, 2010, at 5:04 PM, blue sky wrote:
> On Fri, Feb 12, 2010 at 12:06 PM, Simon Urbanek
> <simon.urbanek at r-project.org> wrote:
>>
>> On Feb 12, 2010, at 12:33 , blue sky wrote:
>>
>>> R-exts.pdf dosen't list many types that are supported in C++, for example,
>>> long. Are there storage.mode corresponds to those extra types?
>>>
>>
>> There are none - that's why they are not listed. As for long: on 32-bit
>> platforms (and Win64) int and long are equivalent so you can simply use
>> INTSXP. On 64-bit unix platforms (LP64) there is no way to losslessly use it
>> (other than raw) but in most applications you can simply use REALSXP as it
>> gives you at least 52-bits of precision which its sufficient for most
>> applications.
>
> According to ?integer,
>
> "Note that on *almost* all implementations of R the range of representable integers is restricted to about +/-2*10^9: ‘double’s can hold much larger integers exactly."
>
> It uses 'almost'. I'm wondering on what platform integer is not restricted to about +/-2*10^9 so that double's can not hold large integers exactly?
>
I'm not sure I can parse your statement including a question, so I'll rather address the two disjoint parts of the quote:
a) restriction of representable integers. Today's platforms use 32-bit integers, but on 16-bit platforms is used to be 16-bit hence the "almost".
b) doubles can hold much larger integers exactly (note that there is no "almost" in this part) -- that is what I was saying above since doubles can store 52-bit integers without loss of precision.
I hope it helps.
Cheers,
Simon
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