'case' seems a lot more useful now than it used to be. Robby
On Tue, Nov 22, 2011 at 10:18 AM, Matthew Flatt <mfl...@cs.utah.edu> wrote: > As of v5.2.0.4, Racket's reader and `datum->syntax' interns literal > strings, byte strings, regexps, characters, and numbers. (Also, > `equal?' now works in the obvious way for regexps.) > > For example, `(eq? "hello" "hello")' will always return true, since the > two literal "hello"s are interned to the same string. Of course, it's > best not to write code that depends on this subtle fact, but the > reader's interning behavior is specified. > > The change is intended to simplify cross-module optimization. The > compiler can now inline an inexact number bound to `pi', for example, > without potentially changing the semantics of a program that uses > something like `(eq? pi pi)'. Probably no good program would break with > cross-module inlining of numbers even without interning, but it seems > simplest to dispense with the question by always interning. > > Along the same lines, I think it's unlikely that good programs are > affected by the `read' interning change, although I had to fix some > Racket tests that specifically check `eq?'-related behavior. Since > `datum->syntax' also interns literals, it's possible that the change > defeats some use of 3-D syntax that depends on the identity of a string > or number; again, though, that seems unlikely. > > Finally, it's unlikely that interning alone will provide any > performance improvement. Fewer copies of strings and numbers may be > retained, but those savings probably just pay for the overhead of the > intern table. > > _________________________________________________ > For list-related administrative tasks: > http://lists.racket-lang.org/listinfo/dev > _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/dev
