1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
|
\name{bitShiftL}
\alias{bitShiftL}
\alias{bitShiftR}
\alias{\%<<\%}
\alias{\%>>\%}
\title{Bitwise Shift Operator (to the Left or Right)}
\description{
These functions shift integers bitwise to the left or to the right,
returning \emph{unsigned int}egers, i.e., values in
\eqn{{0, 1, \ldots, 2^{32}-1}}.
}
\usage{
bitShiftL(a, b)
a \%<<\% b
bitShiftR(a, b)
a \%>>\% b
}
\arguments{
\item{a}{numeric vector (integer valued), to be shifted.}
\item{b}{integer (valued) vector. Internally, only \code{b \%\% 32}
is used, e.g, \code{b = 32} is equivalent to \code{b = 0}, i.e.,
\emph{no} shift. This corresponds to \emph{cyclic} rotation (to the
left or right).}
}
%% \details{
%% }
\value{
non-negative integer valued numeric vector of maximum length of
\code{a} or \code{b} containing
the value of \code{a} shifted to the left or right by \code{b} bits.
NA is returned wherever the value of \code{a} or \code{b} is not finite,
or, wherever the magnitude of \code{a} is greater than or equal to
\eqn{2^{32}}.
}
%\author{ Steve Dutky <sdutky@terpalum.umd.edu> }
\seealso{\code{\link{bitFlip}}, \code{\link{bitXor}}, etc.}
\examples{
bitShiftL(0:4, 1) # 0 2 4 6 8
bitShiftL(0:3, 2) # 0 4 8 12
stopifnot(exprs = {
identical(bitShiftL(0:4, 1), 0:4 \%<<\% 1)
identical(bitShiftR(0:3, 2), 0:3 \%>>\% 2)
})
bitShiftR(0:7, 1) # 0 0 1 1 2 2 3 3 <==> N \%/\% 2
bitShiftR(0:7, 2) # 0 0 0 0 1 1 1 1 <==> N \%/\% 4
## all outputs are "unsigned integer" :
stopifnot( bitShiftL(-1, 0) == 2^32 - 1 ,
bitShiftL(-7, 0) == 4294967289 ,
bitShiftL(-7, 0) == bitShiftR(-7, 0))
bitShiftR(-1,1) == 2147483647
bitShiftL(2147483647,1) == 4294967294 # <==> * 2
bitShiftL( -1, 1) == 4294967294
bitShiftL(47, 32) # is 47
## 5 Christmas trees ( bitShiftL *rotates* to the left)
t(outer(1:5, 0:40, bitShiftL))
N <- as.numeric( rpois(1000, 100) )
stopifnot(identical(bitShiftL(N,0), N),
identical(bitShiftL(N,1), 2*N),
identical(bitShiftL(N,2), 4*N),
## right shift:
identical(bitShiftR(N,2), N \%/\% 4),
identical(bitShiftR(N,4), N \%/\% 16))
}
\keyword{arith}
\keyword{utilities}
|
