How can I remove duplicates in an F# sequence without using references

Question

I have a sorted sequence and want to go through it and return the unique entries in the sequence. I can do it using the following function, but it uses reference variables a

Answer 1

Just initialize a unique collection (like a set) with the sequence like this:

set [1; 2; 3; 3; 4; 5; 5];;
=> val it : Set = set [1; 2; 3; 4; 5]