Julia : where與類型的區別

Dict{String,Array{T,1}} where T; 與Dict{String,Array{T,1}where T}兩種類型的區別
其中，
Dict{String,Array{T,1}} where T，只是說明這個數據類型，只能放一種具體的數據類型，比如Dict{String,Array{Int64,1}}或Dict{String,Array{String,1}}，但不能都放；

Dict{String,Array{T,1}where T}，卻是表明，既可以Dict{String,Array{Int64,1}}，也可以Dict{String,Array{String,1}}；

julia> instrs               = Dict("YLXF"=>[("IC","IH")],"XXXY"=>["IC"])
Dict{
   
   String,Array{
   
   T,1} where T} with 2 entries:
  "XXXY" => ["IC"]
  "YLXF" => [("IC", "IH")]

julia> s = Dict{
   
   String,Array{
   
   T,1} where T}() ;

julia> setindex!(s,["a"],"a")
Dict{
   
   String,Array{
   
   T,1} where T} with 1 entry:
  "a" => ["a"]

julia> setindex!(s,[("a","b")],"b")
Dict{
   
   String,Array{
   
   T,1} where T} with 2 entries:
  "b" => [("a", "b")]
  "a" => ["a"]

julia> Dict{
   
   String,Array{
   
   T,1} where T} == Dict{
   
   String,Array{
   
   T,1}} where T
false

julia> A = Dict{
   
   String,Array{
   
   T,1}} where T
Dict{
   
   String,Array{
   
   T,1}} where T

julia> typeof(A)
UnionAll

julia> B = Dict{
   
   String,Array{
   
   T,1} where T}
Dict{
   
   String,Array{
   
   T,1} where T}

julia> typeof(B)
DataType