3 ms·

Oh great, thanks! Unfortunate that I missed it. Still no luck on the parametric polymorphism though... :(

• im_down_w_otp 10y ago
  That's what Type Variables are explicitly for. They present the necessary semantics for bounded parametric polymorphism. In fact that's really the only reason they exist at all. The rest of the sub-type system works without them, but parametric polymorphism wouldn't work without them. I don't know if the Erlang/Dialyzer docs cover that specifically, but I know the originial paper on Dialyzer and Dialyzer type specs does.
  • bjz_ 10y ago
    I know you can do stuff like: @type pair(t, u) :: {t, u} @type result(t, e) :: {:ok, t} | {:error, e} I'm more talking about type parameters on functions, and also constraining by behaviors and protocols. For example the typespec for Elixir's Stream.map/2 (http://elixir-lang.org/docs/stable/elixir/Stream.html#map/2 http://elixir-lang.org/docs/stable/elixir/Stream.html#map/2): @spec map(Enumerable.t, (element -> any)) :: Enumerable.t Note all the other similarly unspecific type definitions. In a parametrically polmorphic lang, you could do something like: @spec map[e1: Enumerable, e2: Enumerable](e1.t, (e1.element -> e2.element)) :: e2.t And perhaps even intersections of behaviours and protocols: @spec foo[a: Eq & Ord](a.t, a.t) :: bool ('scuse the Elixir syntax...)