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Convenience functions for vals #23658

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b97506e
Convenience functions for vals
bramtayl Sep 10, 2017
f92e7cc
Added tests
bramtayl Sep 11, 2017
51d7a1d
Undid tests for wrong PR [ci-skip]
bramtayl Sep 11, 2017
fa2e6ee
Addressed comments
bramtayl Sep 11, 2017
ce19d8f
Added tests
bramtayl Sep 11, 2017
d5d1b58
Update operators.jl
bramtayl Sep 11, 2017
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18 changes: 18 additions & 0 deletions base/essentials.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -601,6 +601,24 @@ end

Val(x) = (@_pure_meta; Val{x}())

eltype(::Val{T}) where T = T
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@ararslan ararslan Sep 10, 2017

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This isn't correct. T can be Array{S,N}, in which case eltype(Val{Array{S,N}}) should be S. I'd instead make this eltype(::Val{T}) where {T} = eltype(T).

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@bramtayl bramtayl Sep 10, 2017

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Hmm maybe eltype isn't the right name for what I want. I just want a function that will turn Val{:a}() into :a

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@GregPlowman GregPlowman Sep 11, 2017

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However, might be consistent with this:

Julia-0.7.0-DEV> x = Vector{Array{Int,3}}()
0-element Array{Array{Int64,3},1}

Julia-0.7.0-DEV> eltype(x)
Array{Int64,3}

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@JeffBezanson JeffBezanson Sep 11, 2017

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Val isn't a collection or the type of a collection so eltype is not appropriate here.

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@bramtayl bramtayl Sep 11, 2017

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I mean I could just leave it out this PR, or choose another name? devalue?


(&)(v1::Val{false}, v2::Val{false}) = Val{false}()
(&)(v1::Val{true}, v2::Val{false}) = Val{false}()
(&)(v1::Val{false}, v2::Val{true}) = Val{false}()
(&)(v1::Val{true}, v2::Val{true}) = Val{true}()

(|)(v1::Val{false}, v2::Val{false}) = Val{false}()
(|)(v1::Val{true}, v2::Val{false}) = Val{true}()
(|)(v1::Val{false}, v2::Val{true}) = Val{true}()
(|)(v1::Val, v2::Val) = Val{true}()

!(::Val{false}) = Val{true}()
!(::Val{true}) = Val{false}()

ifelse(switch::Val{false}, new, old) = old
ifelse(switch::Val{true}, new, old) = new

# used by interpolating quote and some other things in the front end
function vector_any(@nospecialize xs...)
n = length(xs)
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18 changes: 18 additions & 0 deletions test/operators.jl
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Expand Up @@ -133,3 +133,21 @@ Base.:(<)(x::TypeWrapper, y::TypeWrapper) = (x.t <: y.t) & (x.t != y.t)
@test TypeWrapper(Int) <= TypeWrapper(Real)
@test !(TypeWrapper(Int) <= TypeWrapper(Float64))
end

vf = Val(false)
vt = Val(true)
@testset "value_logic" begin
@test vf & vf == vf
@test vf & vt == vf
@test vt & vf == vf
@test vt & vt == vt
@test vf | vf == vf
@test vf | vt == vt
@test vt | vf == vt
@test vt | vt == vt
@test !vf == vt
@test !vt == vf
@test ifelse(vf, vt, vf) == vf
@test ifelse(vt, vt, vf) == vt
@test eltype(vt)
end
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