Skip to content

Commit

Permalink
fix inverse(^) domain (#34)
Browse files Browse the repository at this point in the history 
fix inverse(^) domain and more inverse domain fixes

Co-authored-by: David Widmann <[email protected]>
  • Loading branch information
@aplavin @devmotion
aplavin and devmotion authored Sep 16, 2024
1 parent ad56514 commit beb5746
Show file tree
Hide file tree
Showing 4 changed files with 36 additions and 13 deletions.
2 changes: 1 addition & 1 deletion Project.toml
View file
Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
name = "InverseFunctions"
uuid = "3587e190-3f89-42d0-90ee-14403ec27112"
version = "0.1.16"
version = "0.1.17"

[deps]
Dates = "ade2ca70-3891-5945-98fb-dc099432e06a"
Expand Down
20 changes: 13 additions & 7 deletions src/functions.jl
View file
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
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
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))
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

2 comments on commit beb5746

@oschulz
Copy link
Collaborator

Choose a reason for hiding this comment

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

@JuliaRegistrator register

@JuliaRegistrator
Copy link

Choose a reason for hiding this comment

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

Registration pull request created: JuliaRegistries/General/115708

Tip: Release Notes

Did you know you can add release notes too? Just add markdown formatted text underneath the comment after the text
"Release notes:" and it will be added to the registry PR, and if TagBot is installed it will also be added to the
release that TagBot creates. i.e.

@JuliaRegistrator register

Release notes:

## Breaking changes

- blah

To add them here just re-invoke and the PR will be updated.

Tagging

After the above pull request is merged, it is recommended that a tag is created on this repository for the registered package version.

This will be done automatically if the Julia TagBot GitHub Action is installed, or can be done manually through the github interface, or via:

git tag -a v0.1.17 -m "<description of version>" beb5746ac73623803e0c023f5978bae46ba1a6c0
git push origin v0.1.17

Please sign in to comment.