最佳答案
What is the benefit of Keyword Lists?
In elixir we have Maps:
> map = %{:a => "one", :b => "two"} # = %{a: "one", b: "two"}
> map.a # = "one"
> map[:a] # = "one"
We also have Keyword Lists:
> kl = [a: "one", b: "two"] # = [a: "one", b: "two"]
> kl2 = [{:a, "one"},{:b, "two"}] # = [a: "one", b: "two"]
> kl == kl2 # = true
> kl[:a] # = "one"
> kl.a # = ** (ArgumentError)
Why both?
Syntax? Is it because Keyword Lists have a more flexible syntax allowing them to be defined without curlys and even without brackets as the last param of a function call? Then why not give Maps this syntactic sugar?
Duplicate Keys? Is it because Keyword Lists can have duplicate keys? Why would you want both Map style access and duplicate keys?
Performance? Is it because Keyword Lists have better performance? Then why have Maps? And shouldn't maps be more performant at looking up members by key than a list of tuples?
JS Array and Ruby Hash like appearance? Is that it?
I understand that structurally they are different data representations. To me it seems that Keyword Lists in elixir serve to complicate the language through exceptional syntax (3 different syntactic variants), use case overlap with maps, and an unclear benefit.
What is the benefit of using Keyword Lists?
