You may have some trouble following this long discussion :-)
Of course set difference is available, but we may need it for arrays and sequences. The plain solution converting the seqs to set, do difference operation and convert back is not always what we want, as we may want to preserve duplicates and order. As I was aware of the naming problem, I had some hope that the desired proc may exist with different name already. Unfortunately miram led the discussion in a very different and wired direction and confused me and maybe many others. The solution from zoom is not bad, I hope I will remember it.
