Merge pull request #19760 from JuliaLang/dbeach24-djcb/bugfix-16706-2

Allow bitarray to handle shifts by a negative value.
JuliaLang · Jan 2, 2017 · 8f9036a · 8f9036a
2 parents 1c605d2 + f041c62
commit 8f9036a
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Showing 2 changed files with 10 additions and 3 deletions.
diff --git a/base/bitarray.jl b/base/bitarray.jl
@@ -1423,23 +1423,28 @@ 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

diff --git a/test/bitarray.jl b/test/bitarray.jl
@@ -1067,6 +1067,8 @@ 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))