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Avoid silent overflow in /(x::Rational, y::Complex{Int}) #53453

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Avoid silent overflow in /(x::Rational, y::Complex{Int}) #53453

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22643eb
complex division by rational inf
nhz2 Feb 23, 2024
b332488
add overflow test
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fix whitespace
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Merge branch 'master' into nz/complex-rational-div-1
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More specific fix
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simplify changes
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Update base/rational.jl
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6 changes: 3 additions & 3 deletions base/rational.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -408,9 +408,9 @@ function *(y::Integer, x::Rational)
yn, xd = divgcd(promote(y, x.den)...)
unsafe_rational(checked_mul(yn, x.num), xd)
end
/(x::Rational, y::Union{Rational, Integer, Complex{<:Union{Integer,Rational}}}) = x//y
/(x::Union{Integer, Complex{<:Union{Integer,Rational}}}, y::Rational) = x//y
inv(x::Rational{T}) where {T} = checked_den(x.den, x.num)
/(x::Rational, y::Union{Rational, Integer}) = x//y
/(x::Integer, y::Rational) = x//y
inv(x::Rational) = checked_den(x.den, x.num)
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fma(x::Rational, y::Rational, z::Rational) = x*y+z

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15 changes: 15 additions & 0 deletions test/rational.jl
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Expand Up @@ -203,6 +203,21 @@ end
end

@test Rational(rand_int, 3)/Complex(3, 2) == Complex(Rational(rand_int, 13), -Rational(rand_int*2, 39))
@test (true//true) / complex(false, true) === 0//1 - 1//1*im
@test (false//true) / complex(false, true) === 0//1 + 0//1*im
@test (false//true) / complex(true, false) === 0//1 + 0//1*im
@test (false//true) / complex(true, true) === 0//1 + 0//1*im
@test (true//true) / complex(true, true) === 1//2 - 1//2*im
@test (false//true) / complex(true//true, true//true) === 0//1 + 0//1*im
@test (true//true) / complex(true//true, true//true) === 1//2 - 1//2*im
@test (false//true) / complex(true//false, false//true) === 0//1 + 0//1*im
@test (true//true) / complex(true//true, true//false) === 0//1 + 0//1*im
@test_throws DivideError (0//1) / complex(0, 0)
@test_throws DivideError (1//1) / complex(0, 0)
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@nsajko nsajko Oct 19, 2024 •
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This is wrong. The correct result is positive infinity, just like here:

julia> (1 // 1) / 0
1//0

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With complex numbers, there are many possible infinities, I'm not sure what infinity is correct.

julia> 1.0/(0.0im)
NaN + NaN*im

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Ref: #22983
https://discourse.julialang.org/t/why-inv-complex-0-0-0-0-returns-complex-nan-nan/92694/1

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You're right, sorry.

@test_throws DivideError (1//0) / complex(0, 0)

# 1//200 - 1//200*im cannot be represented as Complex{Rational{Int8}}
@test_throws OverflowError (Int8(1)//Int8(1)) / (Int8(100) + Int8(100)im)

@test Complex(rand_int, 0) == Rational(rand_int)
@test Rational(rand_int) == Complex(rand_int, 0)
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