Skip to content

fix inverse(^) domain #34

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 11 commits into from
Sep 16, 2024
Merged

fix inverse(^) domain #34

Show file tree
Hide file tree
Changes from 10 commits
Commits
Show all changes
11 commits
Select commit Hold shift + click to select a range
ff3852c
fix inverse(^) domain
aplavin Jul 13, 2023
ba8e13d
more inverse domain fixes
aplavin Nov 25, 2023
a23b811
Update src/functions.jl
aplavin Aug 20, 2024
3d4be83
Update src/functions.jl
aplavin Aug 20, 2024
7db1ae3
Update src/inverse.jl
aplavin Aug 20, 2024
415d4c3
Update src/inverse.jl
aplavin Aug 20, 2024
157f7f0
fix
aplavin Aug 21, 2024
3f093b8
add tests
aplavin Sep 13, 2024
504cc39
Merge branch 'master' into patch-2
aplavin Sep 13, 2024
d99f067
test
aplavin Sep 14, 2024
50f3fca
bump
aplavin Sep 16, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
20 changes: 13 additions & 7 deletions src/functions.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -13,18 +13,20 @@ function square(x)
end



function invpow_arg2(x::Number, p::Real)
if is_real_type(typeof(x))
x ≥ zero(x) ? x^inv(p) : # x > 0 - trivially invertible
isinteger(p) && isodd(Integer(p)) ? copysign(abs(x)^inv(p), x) : # p odd - invertible even for x < 0
throw(DomainError(x, "inverse for x^$p is not defined at $x"))
else
# complex x^p is invertible only for p = 1/n
# complex x^p is only invertible for p = 1/n
isinteger(inv(p)) ? x^inv(p) : throw(DomainError(x, "inverse for x^$p is not defined at $x"))
end
end

function invpow_arg1(b::Real, x::Real)
# b < 0 should never happen in actual use: this check is done in inverse(f)
if b ≥ zero(b) && x ≥ zero(x)
log(b, x)
else
Expand All @@ -33,15 +35,19 @@ function invpow_arg1(b::Real, x::Real)
end

function invlog_arg1(b::Real, x::Real)
if b ≥ zero(b)
b^x
else
throw(DomainError(x, "inverse for log($b, x) is not defined at $x"))
end
# exception may happen here: check cannot be done in inverse(f) because of log(Real, Complex)
b > zero(b) && !isone(b) || throw(DomainError(x, "inverse for log($b, x) is not defined at $x"))
b^x
end
invlog_arg1(b::Number, x::Number) = b^x

invlog_arg2(b::Number, x::Number) = x^inv(b)

function invlog_arg2(b::Real, x::Real)
# exception may happen here: check cannot be done in inverse(f) because of log(Complex, Real)
x > zero(x) && !isone(x) || throw(DomainError(x, "inverse for log($b, x) is not defined at $x"))
x^inv(b)
end
invlog_arg2(b, x) = x^inv(b)


function invdivrem((q, r)::NTuple{2,Number}, divisor::Number)
Expand Down
11 changes: 9 additions & 2 deletions src/inverse.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -159,17 +159,24 @@ inverse(::typeof(sqrt)) = square
inverse(::typeof(square)) = sqrt

inverse(::typeof(cbrt)) = Base.Fix2(^, 3)

inverse(f::Base.Fix2{typeof(^)}) = iszero(f.x) ? throw(DomainError(f.x, "Cannot invert x^$(f.x)")) : Base.Fix2(invpow_arg2, f.x)
inverse(f::Base.Fix2{typeof(^), <:Integer}) = isodd(f.x) ? Base.Fix2(invpow_arg2, f.x) : throw(DomainError(f.x, "Cannot invert x^$(f.x)"))
inverse(f::Base.Fix2{typeof(invpow_arg2)}) = Base.Fix2(^, f.x)

inverse(f::Base.Fix1{typeof(^), <:Real}) = f.x > zero(f.x) ? Base.Fix1(invpow_arg1, f.x) : throw(DomainError(f.x, "Cannot invert $(f.x)^x"))
inverse(f::Base.Fix1{typeof(^)}) = Base.Fix1(invpow_arg1, f.x)
inverse(f::Base.Fix1{typeof(invpow_arg1)}) = Base.Fix1(^, f.x)
inverse(f::Base.Fix1{typeof(log)}) = Base.Fix1(invlog_arg1, f.x)
inverse(f::Base.Fix1{typeof(log)}) = isone(f.x) ? throw(DomainError(f.x, "Cannot invert log($(f.x), x)")) : Base.Fix1(invlog_arg1, f.x)
inverse(f::Base.Fix1{typeof(invlog_arg1)}) = Base.Fix1(log, f.x)
inverse(f::Base.Fix2{typeof(log)}) = Base.Fix2(invlog_arg2, f.x)

inverse(f::Base.Fix2{typeof(log)}) = isone(f.x) ? throw(DomainError(f.x, "Cannot invert log(x, $(f.x))")) : Base.Fix2(invlog_arg2, f.x)
inverse(f::Base.Fix2{typeof(invlog_arg2)}) = Base.Fix2(log, f.x)


inverse(f::Base.Fix2{typeof(divrem)}) = Base.Fix2(invdivrem, f.x)
inverse(f::Base.Fix2{typeof(invdivrem)}) = Base.Fix2(divrem, f.x)

inverse(f::Base.Fix2{typeof(fldmod)}) = Base.Fix2(invfldmod, f.x)
inverse(f::Base.Fix2{typeof(invfldmod)}) = Base.Fix2(fldmod, f.x)

Expand Down
16 changes: 13 additions & 3 deletions test/test_inverse.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -49,7 +49,7 @@ end
x = rand()
for f in (
foo, inv_foo, log, log2, log10, log1p, sqrt,
Base.Fix2(^, rand()), Base.Fix2(^, rand([-10:-1; 1:10])), Base.Fix1(^, rand()), Base.Fix1(log, rand()), Base.Fix1(log, 1/rand()), Base.Fix2(log, rand()),
Base.Fix2(^, 3*rand() - 0.5), Base.Fix2(^, rand(float.([-10:-1; 1:10]))), Base.Fix1(^, rand()), Base.Fix1(log, rand()), Base.Fix1(log, 1/rand()), Base.Fix2(log, rand()),
)
InverseFunctions.test_inverse(f, x)
end
Expand Down Expand Up @@ -92,6 +92,17 @@ end
@test_throws DomainError inverse(Base.Fix2(^, 0.51))(complex(-5))
@test_throws DomainError inverse(Base.Fix2(^, 2))(complex(-5))
InverseFunctions.test_inverse(Base.Fix2(^, 0.5), complex(-5))
@test_throws DomainError inverse(Base.Fix2(^, 2))
@test_throws DomainError inverse(Base.Fix2(^, -4))
Copy link
Member

@devmotion devmotion Aug 20, 2024

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Are the errors for Base.Fix1(^ and log tested somewhere?

Copy link
Collaborator

@oschulz oschulz Aug 21, 2024

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

@aplavin I think there's not test for that yet, correct?

InverseFunctions.test_inverse(Base.Fix2(^, 2.0), 4)
@test_throws DomainError inverse(Base.Fix1(^, 2.0))(-4)
@test_throws DomainError inverse(Base.Fix1(^, -2.0))(4)
@test_throws DomainError inverse(Base.Fix1(^, 0))(4)
@test_throws DomainError inverse(Base.Fix1(log, -2))(4)
@test_throws DomainError inverse(Base.Fix1(log, 1))(4)
@test_throws DomainError inverse(Base.Fix2(^, 0))(4)
@test_throws DomainError inverse(Base.Fix2(log, -2))(4)
@test_throws DomainError inverse(Base.Fix2(log, 1))(4)
InverseFunctions.test_inverse(Base.Fix2(^, -1), complex(-5.))
@test_throws DomainError inverse(Base.Fix2(^, 2))(-5)
@test_throws DomainError inverse(Base.Fix1(^, 2))(-5)
Expand Down Expand Up @@ -143,11 +154,10 @@ end
InverseFunctions.test_inverse(sqrt, x)
@test_throws DomainError inverse(sqrt)(-x)

InverseFunctions.test_inverse(Base.Fix2(^, 2), x)
@test_throws DomainError inverse(Base.Fix2(^, 2))(-x)
InverseFunctions.test_inverse(Base.Fix2(^, 3), x)
InverseFunctions.test_inverse(Base.Fix2(^, 3), -x)
InverseFunctions.test_inverse(Base.Fix2(^, -3.5), x)
@test_throws DomainError inverse(Base.Fix2(^, 2))(-x)
end

@testset "dates" begin
Expand Down