On Tue, Sep 8, 2009 at 3:36 AM, Carl Eastlund<carl.eastl...@gmail.com> wrote: > On Mon, Sep 7, 2009 at 7:01 PM, Jacob Matthews<jac...@cs.uchicago.edu> wrote: >> On Sun, Sep 6, 2009 at 3:14 PM, Robby >> Findler<ro...@eecs.northwestern.edu> wrote: >>> Right. That wouldn't be parametric. >> >> I think it's the contracts-don't-change-programs condition, not the >> parametricity condition, that would be violated here. >> >> -jacob > > Don't these contracts already change the program? I thought, since > Robby indicated that "stacks" cannot be used as lists, these contracts > would be wrapping the values in opaque structs for outside observers. > Adding or removing the contracts changes how a list-implemented stack > responds to list?. Or have I misunderstood the behavior of #:exists > contracts?
You have understood. list? is a problem. It should blow up on these contracts and, if you use the scheme/exists language (as mentioned in the docs I pointed to) it would blow up. Robby _________________________________________________ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-dev
