How does 'unique' work in the TotallyLazy library

How can I use the 'unique' method in the TotallyLazy library for Java and Objective-C?

I have the following code, but I cannot complete it because I'm not sure how the Callable1 instance passed into 'unique' should be composed. Here's what I have so far:

        seq
        .sort(new Comparator<T>() {
            @Override
            public int compare(
                final T pt1,
                final T pt2
            ) {
                return pt1.compareTo(pt2);
            }
        })
        .unique(new Callable1<T,T>() {
            @Override
            public T call(final T pt) throws Exception {
                final int result = pt.compareTo(..?);
                return result != 0;
            }});

As you can see, I can sort successfully, but when it comes to "result = ..." in the 'unique' call, what should I put?

Firstly for sorting you should probably use one of the provided Comparators:

seq.sort(Comparators.<T>ascending());

Then you could just unique with no arguments if uniqueness is based on equality of T as a whole. The overload for unique allows one to get a unique sequence based on some property of T.

For example if you had a Sequence<User> you could say I want them to be unique based on their firstName field:

class User { 
    String firstName, lastName; 
    User(...){...} // Constructor
}

sequence(new User("Chris", "Nash")).unique(user -> user.firstName) 

TotallyLazy has extensive Tests that document the features but the first place to start would always be the SequenceTest or have a look in the whole test package for more examples.