数组和向量之间的区别 [英] Difference between Array and Vector

问题描述

Array和Vector之间是否有区别?

typeof(Array([1,2,3]))
Vector{Int64}

typeof(Vector([1,2,3]))
Vector{Int64}

两者似乎都可以创建相同的东西，但是它们并不相同:

Both seem to create the same thing, but they are not the same:

Array == Vector
false

Array === Vector
false

那么，实际上有什么区别?

So, what is actually the difference?

推荐答案

区别在于Vector是一维Array，因此当您编写例如Vector{Int}这是Array{Int, 1}的简写:

The difference is that Vector is a 1-dimensional Array, so when you write e.g. Vector{Int} it is a shorthand to Array{Int, 1}:

julia> Vector{Int}
Array{Int64,1}

当您调用构造函数Array([1,2,3])和Vector([1,2,3])时，在向其传递向量时，它们会在内部转换为相同的调用Array{Int,1}([1,2,3]).

When you call constructors Array([1,2,3]) and Vector([1,2,3]) they internally get translated to the same call Array{Int,1}([1,2,3]) as you passed a vector to them.

如果要传递非一维数组，您会看到不同之处:

You would see the difference if you wanted to pass an array that is not 1-dimensional:

julia> Array(ones(2,2))
2×2 Array{Float64,2}:
 1.0  1.0
 1.0  1.0

julia> Vector(ones(2,2))
ERROR: MethodError: no method matching Array{T,1} where T(::Array{Float64,2})

还要注意以下效果:

julia> x=[1,2,3]
3-element Array{Int64,1}:
 1
 2
 3

julia> Vector(x)
3-element Array{Int64,1}:
 1
 2
 3

julia> Vector(x) === x
false

因此，呼叫Vector(x)本质上是x的副本.通常，在代码中，您可能只写copy(x).

So essentially the call Vector(x) makes a copy of x. Usually in the code you would probably simply write copy(x).

一般规则是Array是参数类型，具有用花括号括起来的两个参数:

A general rule is that Array is a parametric type that has two parameters given in curly braces:

• 第一个是元素类型(您可以使用eltype进行访问)
• 第二个是数组的维数(您可以使用ndims访问它)

• the first one is element type (you can access it using eltype)
• the second one is the dimension of the array (you can access it using ndims)

请参阅 https://docs.julialang.org/en/v1/manual /arrays/了解详情.

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