On Thu, Apr 2, 2009 at 6:11 PM, Per Bothner <p...@bothner.com> wrote:
> > A number of JVM-based languages implement tail-call elimination. > The problem is that you have to compile your functions into a > different calling convention that the natural. which has some > performance cost, and complicates interoperability. > > Kawa supports two calling conventions, selected by a command-line > switch: > (1) The "obvious" one where a Scheme function call is translated to > a plain method call, with the methods return value being the Scheme > function's result. > (2) Full tail-call support using an extra hidden method argument > that points to a CallContext object. A call is translated thus: > - The parameters are evaluated, and copied into the CallContext. > - The function to be called is evaluated and saved in the CallContext. > - The calling function returns. > - That function's caller implements a "trampoline" (see > http://en.wikipedia.org/wiki/Tail_recursion and > http://en.wikipedia.org/wiki/Trampoline_%28computers%29 ) > which then calls the function saved in the CallContext. > - The callee methods extracts its arguments from the CallContext. > > This is obviously a bit slower, but not so much slower as > to be unusable. (The CallContext API isn't as tweaked as > it should be.) > > On 04/02/2009 09:46 AM, Ben Evans wrote: > > As I understand it, it is not currently possible to implement > > Scheme fully on the JVM, as the Scheme spec requires compilers to > > make a form of the above MUST guarantee (I am not a Scheme head, so > > > if this is too much of a simplification, someone please put me right). > > You're right about Scheme, but wrong about it not being possible > to implement Scheme fully on the JVM. Ah yes, I should have said "whilst maintaining standard calling conventions". Thanks for the catch, Ben --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "JVM Languages" group. To post to this group, send email to jvm-languages@googlegroups.com To unsubscribe from this group, send email to jvm-languages+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/jvm-languages?hl=en -~----------~----~----~----~------~----~------~--~---
