如何在Elixir中键入规范泛型

Question

I have an implementation of a Balanced Search Tree in elixir which serves as a key value store.

I have a method from_list which takes a list of key value tuples and returns a tree with them. Is there a way to use generics to typespec this the way I would do in a strongly typed language?

@spec from_list([{key_type, value_type}]) :: tree(key_type, value_type)
def from_list(list), do: 

When I try this I get an error. Are there generics in Elixir? Or do I have to just make it a list of type {any, any}?

Answer 1

@spec from_list([{key_type, value_type}]) :: tree(key_type, value_type) when key_type: var, value_type: var

From Typespecs — Elixir [latest] :

Guards can be used to restrict type variables given as arguments to the function.

 @spec function(arg) :: [arg] when arg: atom 

If you want to specify more than one variable, you separate them by a comma.

 @spec function(arg1, arg2) :: [arg1, arg2] when arg1: atom, arg2: integer 

Type variables with no restriction can also be defined using var .

 @spec function(arg) :: [arg] when arg: var