[plt-scheme] PLT4 expectations

Matthew Flatt writes:
 > At Tue, 11 Mar 2008 01:01:08 -0400, Doug Orleans wrote:
 > > Matthew Flatt writes:
 > >  > At Mon, 10 Mar 2008 14:34:49 +0000, "Paulo J. Matos" wrote:
 > >  > > The idea of PLT4 creating by default immutable pairs and the so, means
 > >  > > that it also opens the possibility for far more and better
 > >  > > optimizations in the compiler, right?
 > >  > 
 > >  > I doubt that there are many new optimization opportunities that matter
 > >  > in practice.
 > > 
 > > Well, you could make "list?" be O(1) instead of O(n), at a cost of one
 > > bit per cons cell.
 > 
 > Yes, `list?' is currently amortized constant time.

That's great!  I instinctively avoid "list?" (and <list> specializers
in Swindle), but now I will stop being afraid.

How about "length" and "last"?  Or would those be too expensive in space?

--dougorleans at gmail.com