[m-users.] is there a easy way to wrap Erlang's improper_list/2 and something similar?

[Xiaofeng Yang]

hi, all

I'm new to Mercury and trying to use it as a language on Erlang VM with
strict and obligatory static checker. I've tried to wrap the basic list
types in Erlang but failed. The following is what I've done. I know the
definitions are wrong. But I don't know how to wrap the improper lists in
an easy, expressive, efficient way so that I can use them like how I use
them in Erlang. Please help me or point me how to solve this problem.
Thanks.

In Mercury:

%% nonempty_improper_list()
:- type erlang_nonempty_improper_list(Contents, Termination) --->
          [Contents | Termination]
        ; [Contents | erlang_nonempty_improper_list(Contents, Termination)].

%% wrap improper_list()
:- type erlang_improper_list(Contents, Termination) --->
          erlang_improper_list( Termination )           % can't use
Termination directly
        ; erlang_improper_list( erlang_nonempty_improper_list(Contents,
Termination) ).

But I can write this in Erlang:

-type erlang_nonempty_improper_list(Contents, Termination) ::
          [Contents | Termination]
        | [Contents | erlang_nonempty_improper_list(Contents, Termination)].

%% improper_list() wrapping
-type erlang_improper_list(Contents, Termination) ::
          Termination
        | erlang_nonempty_improper_list(Contents, Termination).


     Best regards,
Xiaofeng Yang
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