Julia - #undef か否かを調べる

環境

• Julia 1.3.0

配列の要素が undef か否かを調べる時は isassigned を使う

Arrays · The Julia Language

julia> v = Vector{Any}(undef, 5)
5-element Array{Any,1}:
 #undef
 #undef
 #undef
 #undef
 #undef

julia> v[1:3] .= 'a':'c'
3-element view(::Array{Any,1}, 1:3) with eltype Any:
 'a'
 'b'
 'c'

julia> v[1:3] = 'a':'c'
'a':1:'c'

julia> v
5-element Array{Any,1}:
    'a'
    'b'
    'c'
 #undef
 #undef

julia> v = Vector{Any}(undef, 5)
5-element Array{Any,1}:
 #undef
 #undef
 #undef
 #undef
 #undef

julia> v[1:3] = 'a':'c'
'a':1:'c'

julia> v
5-element Array{Any,1}:
    'a'
    'b'
    'c'
 #undef
 #undef

julia> isassigned(v, 1)
true

julia> isassigned(v, 2)
true

julia> isassigned(v, 3)
true

julia> isassigned(v, 4)
false

julia> isassigned(v, 5)
false