Handle Base.tail & friends
#567
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## main #567 +/- ##
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+ Coverage 93.14% 93.15% +0.01%
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Files 15 15
Lines 875 891 +16
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+ Hits 815 830 +15
- Misses 60 61 +1
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| @@ -78,6 +78,13 @@ end | |||
| @test getindex(Tangent{Tuple{Float64}}(@thunk 2.0^2), 1) == 4.0 | |||
| @test getproperty(Tangent{Tuple{Float64}}(2.0), 1) == 2.0 | |||
| @test getproperty(Tangent{Tuple{Float64}}(@thunk 2.0^2), 1) == 4.0 | |||
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| tang3 = Tangent{Tuple{Float64, String, Vector{Float64}}}(1.0, NoTangent(), @thunk [3.0] .+ 4) | |||
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Should we test this behaviour explicitly?
julia> tang1 = Tangent{Tuple{Float64}}(1.0)
Tangent{Tuple{Float64}}(1.0,)
julia> Base.tail(tang1)
Tangent{Tuple{}}()There was a problem hiding this comment.
Maybe this should just return NoTangent()?
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Maybe, would be consistent with
julia> rand_tangent(())
NoTangent()
src/tangent_types/tangent.jl
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| Base.first(tangent::Tangent{P,T}) where {P,T<:Union{Tuple,NamedTuple}} = first(backing(canonicalize(tangent))) | ||
| Base.last(tangent::Tangent{P,T}) where {P,T<:Union{Tuple,NamedTuple}} = last(backing(canonicalize(tangent))) | ||
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| Base.tail(tangent::Tangent{P}) where {P<:Tuple} = Tangent{_tailtype(P)}(Base.tail(backing(tangent))...) |
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Why is this limited to Tuples only, does NamedTuple not work in some way?
It's also not clear to me why tail is not defined on any primal P (as for first and last). I thought it is because the order is chosen when defining the Tangent, i.e.
julia> Tangent{Foo}(;a=1.0, b=2.0, c=3.0)
Tangent{Foo}(a = 1.0, b = 2.0, c = 3.0)
julia> Tangent{Foo}(;a=1.0,c=3.0, b=2.0)
Tangent{Foo}(a = 1.0, c = 3.0, b = 2.0)which was handled in last by adding canonicalize
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I don't know what this should do for Foo.
Tangent{Foo}(;a=1.0, b=2.0,) is very different to what this does. And very different to indexing; dx[1] does not produce Tangent{Foo}(;a=1.0). Tangents with wrong-order or wrong-length backing are an aberration, and nothing should deliberately produce them.
I didn't add NamedTuples just because they would need a more elaborate _tailtype.
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Now NamedTuples are added.
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Thanks! Formatting and good to go :) |
It would be nice if
Base.tail(::Tangent)worked. Converting to a Tuple isn't safe... I think for example thisfrule:https://github.com/JuliaDiff/ChainRules.jl/blob/main/src/rulesets/Base/indexing.jl#L102-L105
goes wrong if
ẋ isa NoTangent, which might be causing this failure:https://github.com/JuliaDiff/Diffractor.jl/runs/7351650418?check_suite_focus=true#step:6:252