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Allow bitarray to handle shifts by a negative value. #19760

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Jan 2, 2017
Merged

Allow bitarray to handle shifts by a negative value. #19760

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11 changes: 8 additions & 3 deletions base/bitarray.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -1481,23 +1481,28 @@ end

reverse(v::BitVector) = reverse!(copy(v))

function (<<)(B::BitVector, i::Int)

function (<<)(B::BitVector, i::UInt)
n = length(B)
i == 0 && return copy(B)
A = falses(n)
i < n && copy_chunks!(A.chunks, 1, B.chunks, i+1, n-i)
return A
end

function (>>>)(B::BitVector, i::Int)
function (>>>)(B::BitVector, i::UInt)
n = length(B)
i == 0 && return copy(B)
A = falses(n)
i < n && copy_chunks!(A.chunks, i+1, B.chunks, 1, n-i)
return A
end

(>>)(B::BitVector, i::Int) = B >>> i
(>>)(B::BitVector, i::Union{Int, UInt}) = B >>> i

# signed integer version of shift operators with handling of negative values
(<<)(B::BitVector, i::Int) = (i >=0 ? B << unsigned(i) : B >> unsigned(-i))
(>>>)(B::BitVector, i::Int) = (i >=0 ? B >> unsigned(i) : B << unsigned(-i))

"""
rol!(dest::BitVector, src::BitVector, i::Integer) -> BitVector
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2 changes: 2 additions & 0 deletions test/bitarray.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -1069,6 +1069,8 @@ let b1 = bitrand(v1)
for m = [rand(1:v1)-1, 0, 1, 63, 64, 65, 191, 192, 193, v1-1]
@test isequal(b1 << m, [ b1[m+1:end]; falses(m) ])
@test isequal(b1 >>> m, [ falses(m); b1[1:end-m] ])
@test isequal(b1 << -m, b1 >> m)
@test isequal(b1 >>> -m, b1 << m)
@test isequal(rol(b1, m), [ b1[m+1:end]; b1[1:m] ])
@test isequal(ror(b1, m), [ b1[end-m+1:end]; b1[1:end-m] ])
@test isequal(ror(b1, m), rol(b1, -m))
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