To call elixir from Elchemy you need to define a foreing function interface. To do that you can use either ffi or tryFfi macro.

Both ffi and tryFfi require the function to have very specific format, which is:

1. You need to make sure the type signature is correct and adivsably it should contain as simple type structures as possible.
2. There should be no explicit parameters
3. The only of the function should be an ffi call in a format of:

ffi "Module" "function"

A good example of an ffi call would be

upcase : String -> String
upcase =
    ffi "String" "upcase"

A generated code of that statement would be

@spec upcase(String.t) :: String.t
curry upcase/1
verify as: String.upcase/1
def upcase(a1), do: String.upcase(a1)

Where verify, as: is a type safety generator about which you can read more in testing section.

Another type of ffi is tryFfi, which doesn't ensure any type safety, but it wraps a call in a try..catch clause and returns the result in either {:ok, result} or {:error, err}.