'Char' type problem

[Peter Phelan]

Hello all

I'm trying to get started in Mercury, with a view to porting
substantial amounts of Prolog code.

I have a very simple program, which produces the following
error under mmc --
error: undefined type char/1.

I understood that char was a built in recognised type.
Clealry I've done something wrong.

Any help gladly received.

The prog:

:-module foo1.

:- pred foo1(char(X), char(X)).
:- mode foo1(in, out) is semidet.

foo1(A, B):-
 A = B.


Thanks

Peter Phelan