remove duplicated lists inside list in lisp [duplicate]

Question

How do i remove duplicated lists inside a list in common-lisp? I tried this:

(remove-duplicates '( (1 2 3) (1 2 3)))                           

But it evaluates to ((1 2 3) (1 2 3)), not ((1 2 3)).

Thanks.

Answer 1

Use the keyword argument :test to specify the function that defines whether or not two items are duplicates of each other. Most lisp functions, including remove-duplicates, use eql to test for equality by default. eql is much stricter than equal, which is what you probably want to be using.

 (remove-duplicates '((1 2 3) (1 2 3)) :test #'equal)

This evaluates to '((1 2 3)).

See this post for more detail about the difference between eql and equal.

Answer 2

Try:

(remove-duplicates '((1 2 3) (1 2 3)) :test #'equal)