[mercury-users] Why is

[Jeff Thompson]

Hello.  I would like to check my understanding here.  List member is 
defined as:

member(X, [X | _]).
member(X, [_ | Xs]) :- member(X, Xs).

It is counter-intuitive to me why mode member(in, in) is semidet.  If 
you call member(1, [1, 1]), why doesn't the code above match twice which 
would make this mode nondet?

Thanks for any help,
- Jeff

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