[R] Bitwise operations on large numbers
William Dunlap
wdunlap at tibco.com
Fri Jun 6 00:49:53 CEST 2014
Oops, I got bitSlice wrong, hence and and or won't be right. bitSlice
should be:
bitSlice <- function(x, from, length) shiftR(x, from) %% 2^length
Bill Dunlap
TIBCO Software
wdunlap tibco.com
On Thu, Jun 5, 2014 at 3:31 PM, William Dunlap <wdunlap at tibco.com> wrote:
>> Double allows me to
>> store large numbers but I can not perform bitwise shifting.
>
> It is a nuisance that bitwShiftL and bitwShitR don't just shift (and
> wrap around to negative) for integers so you could use all 32 bits.
> You could use doubles and multiply (*) and divide (%/%) by 2^n instead
> of shifting left and right by n bits. That would give you 52 bits.
> Bitwise 'and' and 'or' with doubles is harder to do efficiently at the
> R level but you can get it done with the following:
>
> shiftL <- function(x, n) x * 2^n
> shiftR <- function(x, n) x %/% 2^n
> or <- function(x, y) .bitOp(x, y, bitwOr)
> and <- function(x, y) .bitOp(x, y, bitwAnd)
> bitSlice <- function(x, from, length) shiftR(x, from) %% 2^(from+length)
> .bitOp <- function(x, y, bitwOp) bitwOp(bitSlice(x, 0, 26),bitSlice(y,
> 0, 26)) + shiftL(bitwOp(bitSlice(x, 26, 26), bitSlice(y, 26, 26)), 26)
> Bill Dunlap
> TIBCO Software
> wdunlap tibco.com
>
>
> On Thu, Jun 5, 2014 at 11:43 AM, Koustubh Bagade <kou.genious at gmail.com> wrote:
>> Hi
>>
>> I am working on numbers between 0 - 2^32. I want to perform bit-wise shift
>> operations on these numbers. Integer allows me to do bitwise shift
>> operations but number range is limited to 0 - 2^31. Double allows me to
>> store large numbers but I can not perform bitwise shifting.
>>
>> I can not change programming language as it is part of larger project.
>>
>> Is there a way to solve this problem? Perhaps using data types similar to
>> unsigned integer or long integer?
>>
>> Thanks
>>
>> Koustubh Bagade
>>
>> [[alternative HTML version deleted]]
>>
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