是否有与 NumPy 的省略号切片语法 (...) 等效的 Julia?
问题描述
在 NumPy 中，省略号语法 用于
In NumPy, the ellipsis syntax is for
填写多个:，直到切片说明符的个数与数组的维度相匹配.
filling in a number of
:until the number of slicing specifiers matches the dimension of the array.
(转述这个答案).
我如何在 Julia 中做到这一点?
How can I do that in Julia?
解决方案
还没有，但如果你愿意，你可以自己动手.
Not yet, but you can help yourself if you want.
import Base.getindex, Base.setindex!
const .. = Val{:...}
setindex!{T}(A::AbstractArray{T,1}, x, ::Type{Val{:...}}, n) = A[n] = x
setindex!{T}(A::AbstractArray{T,2}, x, ::Type{Val{:...}}, n) = A[ :, n] = x
setindex!{T}(A::AbstractArray{T,3}, x, ::Type{Val{:...}}, n) = A[ :, :, n] =x
getindex{T}(A::AbstractArray{T,1}, ::Type{Val{:...}}, n) = A[n]
getindex{T}(A::AbstractArray{T,2}, ::Type{Val{:...}}, n) = A[ :, n]
getindex{T}(A::AbstractArray{T,3}, ::Type{Val{:...}}, n) = A[ :, :, n]
那你就可以写了
> rand(3,3,3)[.., 1]
3x3 Array{Float64,2}:
0.0750793 0.490528 0.273044
0.470398 0.461376 0.01372
0.311559 0.879684 0.531157
如果您想要更精细的切片，您需要生成/扩展定义或使用分段函数.
If you want more elaborate slicing, you need to generate/expand the definition or use staged functions.
如今，请参阅 https://github.com/ChrisRackauckas/EllipsisNotation.jl
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