How to get rid of duplicates in a list, but keep the order

Question

I am using Intermediate Student with Lambda in DrRacket, I was wondering how one would remove the duplicates in a list, while keeping the order. For example (remo

Answer 1

SRFI-1 has delete-duplicates, although it's inefficient. (I am not too familiar with Racket, but surely it has SRFI-1, and the source...)

http://srfi.schemers.org/srfi-1/srfi-1.html#delete-duplicates