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Add reduce_empty definitions for bitwise ops on integers (&, | and xor) #25595

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Add reduce_empty definitions for bitwise ops on integers (&, | and xor) #25595

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Add reduce_empty definitions for bitwise ops on integers (&, | and xor)
simonbyrne Jan 16, 2018
ff67310
Merge branch 'master' into sb/reduce-and
vtjnash Nov 2, 2023
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6 changes: 6 additions & 0 deletions base/reduce.jl
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Expand Up @@ -359,6 +359,12 @@ reduce_empty(::typeof(mul_prod), ::Type{Union{}}) = _empty_reduce_error(mul_prod
reduce_empty(::typeof(mul_prod), ::Type{T}) where {T} = reduce_empty(*, T)
reduce_empty(::typeof(mul_prod), ::Type{T}) where {T<:SmallSigned} = one(Int)
reduce_empty(::typeof(mul_prod), ::Type{T}) where {T<:SmallUnsigned} = one(UInt)
reduce_empty(::typeof(&), ::Type{Bool}) = true
reduce_empty(::typeof(&), ::Type{T}) where {T<:Integer} = -1 % T
reduce_empty(::typeof(|), ::Type{Bool}) = false
reduce_empty(::typeof(|), ::Type{T}) where {T<:Integer} = zero(T)
reduce_empty(::typeof(xor), ::Type{Bool}) = false
reduce_empty(::typeof(xor), ::Type{T}) where {T<:Integer} = zero(T)

reduce_empty(op::BottomRF, ::Type{T}) where {T} = reduce_empty(op.rf, T)
reduce_empty(op::MappingRF, ::Type{T}) where {T} = mapreduce_empty(op.f, op.rf, T)
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10 changes: 8 additions & 2 deletions test/reduce.jl
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Expand Up @@ -11,7 +11,14 @@ using .Main.OffsetArrays
@test foldl(+, Int64[]) === Int64(0) # In reference to issues #7465/#20144 (PR #20160)
@test foldl(+, Int16[]) === Int16(0) # In reference to issues #21536
@test foldl(-, 1:5) == -13
@test foldl(-, 10, 1:5) == -5
@test foldl(-, 1:5; init=10) == -5
@test foldl(&, UInt8[]) === typemax(UInt8)
@test foldl(&, Int8[]) === Int8(-1)
@test foldl(|, UInt8[]) === zero(UInt8)
@test foldl(|, Int8[]) === zero(Int8)
@test foldl(⊻, UInt8[]) === zero(UInt8)
@test foldl(⊻, Int8[]) === zero(Int8)

@test Base.mapfoldl(abs2, -, 2:5) == -46
@test Base.mapfoldl(abs2, -, 2:5; init=10) == -44
Expand Down Expand Up @@ -645,8 +652,7 @@ test18695(r) = sum( t^2 for t in r )

# test neutral element not picked incorrectly for &, |
@test @inferred(foldl(&, Int[1])) === 1
@test_throws ["reducing over an empty",
"consider supplying `init`"] foldl(&, Int[])
@test foldl(&, Int[]) === -1

# prod on Chars
@test prod(Char[]) == ""
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