At Fri, 08 Oct 2010 23:10:05 -0400, David Van Horn wrote: > On 10/8/10 9:12 PM, Matthew Flatt wrote: > > This proposal originates with the need to fix a problem in the HtDP > > teaching languages. The HtDP teaching languages currently use `true' > > and `false' for true and false, and the HtDP languages are configured > > to print booleans as `true' and `false'. That doesn't work with quoted > > lists. For example, > > > > '(true false) > > > > is a list of symbols, not a list of booleans. > > What about '(empty)? Seems like the same issue.
Yes, so we are also looking at how to move away from `empty'. The answer isn't `#empty' --- at least not without breaking the correspondence between an expression E and `eval' of a `quote'd E. For example, we would want `#empty' by itself to mean the empty list, and quoting `#empty' should also mean the empty list, but `eval'ing the empty list should be an empty application, not the empty list. Maybe we have to use '() for the empty list, even in the teaching languages. _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/dev
