Rainman is most definitely not high functioning by today's criteria, but neither AS nor HFA were diagnoses when the movie was made.
Since severe was what autism meant in the 80's, Rainman is probably moderate by today's criteria and as high functioning as it got in the 80's. But that's not how he comes off to me personally, I personally see him as severe.
Whether AS and HFA is the same has been discussed here for years.
I don't consider AS and HFA to be exactly the same. AS is about having no speech delay and no delay in self help skills. To me it's a significant difference between hitting the early mile stones (and not needing any more parental care than most kids, be able to be out alone, go grocery shopping and be home alone for a while as a bigger kid etc), and someone who can't.
It was also supposed to be a difference that AS usually comes with higher verbal IQ and HFA with higher performance IQ.
There used to be a member here who said that the problem with any category you could come up with to differentiate between HFA and AS, any given criteria would be true for about half of both groups.
Three other people I have been in touch with thought there were differences between HFA and AS, including:
- in an autism center aspies wanting to talk about their problems while HFA wanting to play games and have fun
- HFA having poorer speech even as teens (the person saying this based it on an HFA friend he had, he was aspie)
- HFA having less need to participate in chats, being happy to keep their thoughts to themselves, apparently unlike aspies
- aspies having more need to be social than HFA
- aspies being really obsessive about their obsessions while HFA are interested but not obsessive in the same way and less likely to collect things in connection to their interest (if for instance the person likes trains, a HFA would like trains, while an aspie would love trains, think trains, speak of trains, collect trains and train related things ranging from actual models to duvet covers and books (this from two sisters with HFA and AS diagnoses respectively)
Regardless, none of these things will be true only for the members of one of the groups nor for all the members of said group. There might be some differences between HFA and AS but there are likely more similarities than differences.