[MLton] regions

[Henry Cejtin]

Just  to add my 2 cents worth (more like 2/100-ths of a cent), it seems to me
that with regards to MLton performance, much of what regions gives you  is  a
very  clever  way to safely re-use memory instead of waiting for a GC (which,
as Stephen says, really does seem to be needed to be safe for  space,  and  I
really  REALLY  want  space  safety).  I wonder what could be done with MLton
with a `simple' pass to see where space can  be  re-used.   E.g.,  mutate  in
place or some really simple stack region-nursery.

Any way, just a random micro-thought.