:- module ml_lookup_switch_test.
:- interface.

:- type thing
    --->    thing1
    ;       thing2
    ;       nothing
    ;       thing3
    ;       thing4.

:- type category
    --->    cat1
    ;       cat2
    ;       nocat.

:- func classify(category, thing) = category.

:- implementation.

classify(Cat0, Thing) = Cat :-
    (
        ( Thing = thing1
        ; Thing = thing2
        ; Thing = thing3
        ; Thing = thing4
        ),
        (
            ( Thing = thing1
            ; Thing = thing2
            ),
            Cat = cat1
        ;
            ( Thing = thing3
            ; Thing = thing4
            ),
            Cat = cat2
        )
    ;
        Thing = nothing,
        Cat = Cat0
    ).