Julia get!用法及代碼示例

get!(collection, key, default)

返回為給定鍵存儲的值，或者如果不存在該鍵的映射，則存儲 key => default 並返回 default 。

例子

julia> d = Dict("a"=>1, "b"=>2, "c"=>3);

julia> get!(d, "a", 5)
1

julia> get!(d, "d", 4)
4

julia> d
Dict{String, Int64} with 4 entries:
  "c" => 3
  "b" => 2
  "a" => 1
  "d" => 4

get!(f::Function, collection, key)

返回為給定鍵存儲的值，或者如果不存在該鍵的映射，則存儲 key => f() 並返回 f() 。

這旨在使用do 塊語法調用。

例子

julia> squares = Dict{Int, Int}();

julia> function get_square!(d, i)
           get!(d, i) do
               i^2
           end
       end
get_square! (generic function with 1 method)

julia> get_square!(squares, 2)
4

julia> squares
Dict{Int64, Int64} with 1 entry:
  2 => 4