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Make π < π work as expected #27797

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Jun 27, 2018
Merged

Make π < π work as expected #27797

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c0da690
Make π < π work as expected
perrutquist Jun 26, 2018
06ccadd
MethodError instead of AssertionError from <
perrutquist Jun 26, 2018
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11 changes: 11 additions & 0 deletions base/irrationals.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -56,6 +56,17 @@ float(::Type{<:AbstractIrrational}) = Float64
==(::Irrational{s}, ::Irrational{s}) where {s} = true
==(::AbstractIrrational, ::AbstractIrrational) = false

<(::Irrational{s}, ::Irrational{s}) where {s} = false
function <(x::AbstractIrrational, y::AbstractIrrational)
# If two different Irrationals round to the same Float64, then explicit
# < methods are needed for those inputs, as the below assertation will fail.
@assert Float64(x) != Float64(y)
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This should probably throw some specific error.

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Probably a good idea. Something like

Float64(x) != Float64(y) || error("$x and $y have identical Float64 representations")

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Or a MethodError. The solution is to add a specific method, after all.

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I've added a commit, changing the code to throw a MethodError.

return Float64(x) < Float64(y)
end

<=(::Irrational{s}, ::Irrational{s}) where {s} = true
<=(x::AbstractIrrational, y::AbstractIrrational) = x==y || x<y

# Irrationals, by definition, can't have a finite representation equal them exactly
==(x::AbstractIrrational, y::Real) = false
==(x::Real, y::AbstractIrrational) = false
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13 changes: 13 additions & 0 deletions test/numbers.jl
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Expand Up @@ -999,6 +999,19 @@ end
@test !(1 > NaN)
end

@testset "Irrationals compared with Irrationals" begin
for i in (π, ℯ, γ, catalan)
for j in (π, ℯ, γ, catalan)
@test isequal(i==j, Float64(i)==Float64(j))
@test isequal(i!=j, Float64(i)!=Float64(j))
@test isequal(i<=j, Float64(i)<=Float64(j))
@test isequal(i>=j, Float64(i)>=Float64(j))
@test isequal(i<j, Float64(i)<Float64(j))
@test isequal(i>j, Float64(i)>Float64(j))
end
end
end

@testset "Irrationals compared with Rationals and Floats" begin
@test Float64(pi,RoundDown) < pi
@test Float64(pi,RoundUp) > pi
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