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Make inv(::Complex) return zero when input has Inf magnitude #32050

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Jun 5, 2019
Merged

Make inv(::Complex) return zero when input has Inf magnitude #32050

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9 changes: 7 additions & 2 deletions base/complex.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -259,7 +259,11 @@ julia> conj(1 + 3im)
conj(z::Complex) = Complex(real(z),-imag(z))
abs(z::Complex) = hypot(real(z), imag(z))
abs2(z::Complex) = real(z)*real(z) + imag(z)*imag(z)
inv(z::Complex) = conj(z)/abs2(z)
function inv(z::Complex)
c, d = reim(z)
(isinf(c) | isinf(d)) && return complex(copysign(zero(c), c), flipsign(-zero(d), d))
complex(c, -d)/(c * c + d * d)
end
inv(z::Complex{<:Integer}) = inv(float(z))

+(z::Complex) = Complex(+real(z), +imag(z))
Expand Down Expand Up @@ -346,7 +350,7 @@ function /(a::Complex{T}, b::Complex{T}) where T<:Real
end

inv(z::Complex{<:Union{Float16,Float32}}) =
oftype(z, conj(widen(z))/abs2(widen(z)))
oftype(z, inv(widen(z)))

/(z::Complex{T}, w::Complex{T}) where {T<:Union{Float16,Float32}} =
oftype(z, widen(z)*inv(widen(w)))
Expand Down Expand Up @@ -430,6 +434,7 @@ end

function inv(w::ComplexF64)
c, d = reim(w)
(isinf(c) | isinf(d)) && return complex(copysign(0.0, c), flipsign(-0.0, d))
half = 0.5
two = 2.0
cd = max(abs(c), abs(d))
Expand Down
40 changes: 40 additions & 0 deletions test/complex.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -999,6 +999,46 @@ end
end
end

@testset "division by Inf, issue#23134" begin
@testset "$T" for T in (Float32, Float64, BigFloat)
@test isequal(one(T) / complex(T(Inf)), complex(zero(T), -zero(T)))
@test isequal(one(T) / complex(T(Inf), one(T)), complex(zero(T), -zero(T)))
@test isequal(one(T) / complex(T(Inf), T(NaN)), complex(zero(T), -zero(T)))
@test isequal(one(T) / complex(T(Inf), T(Inf)), complex(zero(T), -zero(T)))

@test isequal(one(T) / complex(T(-Inf)), complex(-zero(T), -zero(T)))
@test isequal(one(T) / complex(T(-Inf), one(T)), complex(-zero(T), -zero(T)))
@test isequal(one(T) / complex(T(-Inf), T(NaN)), complex(-zero(T), -zero(T)))
@test isequal(one(T) / complex(T(-Inf), T(Inf)), complex(-zero(T), -zero(T)))

@test isequal(one(T) / complex(T(Inf),-zero(T)), complex(zero(T), zero(T)))
@test isequal(one(T) / complex(T(Inf),-one(T)), complex(zero(T), zero(T)))
@test isequal(one(T) / complex(T(Inf),T(-NaN)), complex(zero(T), zero(T)))
@test isequal(one(T) / complex(T(Inf),T(-Inf)), complex(zero(T), zero(T)))

@test isequal(one(T) / complex(T(-Inf),-zero(T)),complex(-zero(T), zero(T)))
@test isequal(one(T) / complex(T(-Inf),-one(T)), complex(-zero(T), zero(T)))
@test isequal(one(T) / complex(T(-Inf),T(-NaN)), complex(-zero(T), zero(T)))
@test isequal(one(T) / complex(T(-Inf),T(-Inf)), complex(-zero(T), zero(T)))

@test isequal(one(T) / complex(zero(T), T(Inf)), complex(zero(T), -zero(T)))
@test isequal(one(T) / complex(one(T), T(Inf)), complex(zero(T), -zero(T)))
@test isequal(one(T) / complex(T(NaN), T(Inf)), complex(zero(T), -zero(T)))

@test isequal(one(T) / complex(zero(T), T(-Inf)), complex(zero(T), zero(T)))
@test isequal(one(T) / complex(one(T), T(-Inf)), complex(zero(T), zero(T)))
@test isequal(one(T) / complex(T(NaN), T(-Inf)), complex(zero(T), zero(T)))

@test isequal(one(T) / complex(-zero(T), T(Inf)), complex(-zero(T), -zero(T)))
@test isequal(one(T) / complex(-one(T), T(Inf)), complex(-zero(T), -zero(T)))
@test isequal(one(T) / complex(T(-NaN), T(Inf)), complex(-zero(T), -zero(T)))

@test isequal(one(T) / complex(-zero(T), T(-Inf)), complex(-zero(T), zero(T)))
@test isequal(one(T) / complex(-one(T), T(-Inf)), complex(-zero(T), zero(T)))
@test isequal(one(T) / complex(T(-NaN), T(-Inf)), complex(-zero(T), zero(T)))
end
end

@testset "complex^real, issue #14342" begin
for T in (Float32, Float64, BigFloat), p in (T(-21//10), -21//10)
z = T(2)+0im
Expand Down