bitops (version 1.0-9)

bitShiftL: Bitwise Shift Operator (to the Left or Right)

Description

These functions shift integers bitwise to the left or to the right, returning unsigned integers, i.e., values in $0,1,\dots ,2^{32}-1$.

Usage

bitShiftL(a, b)
a %<<% b="" bitshiftr(a,="" b)="" a="" %="">>% b

Value

non-negative integer valued numeric vector of maximum length of

a or b containing the value of a shifted to the left or right by b bits. NA is returned wherever the value of a or b is not finite, or, wherever the magnitude of a is greater than or equal to

$2^{32}$.

Arguments

a

numeric vector (integer valued), to be shifted.

b

integer (valued) vector. Internally, only b %% 32 is used, e.g, b = 32 is equivalent to b = 0, i.e., no shift. This corresponds to cyclic rotation (to the left or right).

See Also

bitFlip, 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))