These last posts cleared it up. Thanks.
Which remind me, I think one of the SICP lectures on youtube mentions
tail calls to *other* functions, which I totally forgot, with an
example of a person doing something for another doing something for
another... and the last one just gives the result to the first. That
ain't no internal loop.
On Jan 26, 1:23 pm, Laurent PETIT <laurent.pe...@gmail.com> wrote:
> 2011/1/26 Alan <a...@malloys.org>:
>
> > Now try writing two mutually-recursive functions. In Scheme (as I
> > understand it) that will get optimized into a jump from one function
> > to the other, while in Clojure it will use the stack.
>
> And that's why Rich introduced clojure.core/trampoline.
>
> Cheers,
>
> --
> Laurent
>
>
>
>
>
> > On Jan 26, 1:10 pm, Armando Blancas <armando_blan...@yahoo.com> wrote:
> >> From SICP: "With a tail-recursive implementation, iteration can be
> >> expressed using the ordinary procedure call mechanism". As I
> >> understand this, a tail call is a loop with functional notation but
> >> not actually a function call. That's why I find this issue difficult
> >> to follow, since loops are internal details of a function/method and
> >> don't get involved with calls, stack frames, access security, or how
> >> the jit-compiled code may or may not be optimized. So there's
> >> something key here that I'm missing.
>
> >> In a little project of mine I plan on doing this (hand-coded with ASM
> >> as my compiler doesn't do TCO yet). That seems to work but I wonder
> >> what issues may come up.
>
> >> int fact(int n, int r) {
> >> if (n == 0) return r;
> >> else return fact(n-1, n*r);}
>
> >> 0: iload_0
> >> 1: ifne 6
> >> 4: iload_1
> >> 5: ireturn
> >> 6: iload_0
> >> 7: istore_2 // temp for n
> >> 8: iload_2
> >> 9: iconst_1
> >> 10: isub
> >> 11: istore_0
> >> 12: iload_2
> >> 13: iload_1
> >> 14: imul
> >> 15: istore_1
> >> 16: goto 0
>
> >> On Jan 26, 11:20 am, Luc Prefontaine <lprefonta...@softaddicts.ca>
> >> wrote:
>
> >> > From what I recall from a previous thread it would require so much byte
> >> > code tweaking that
> >> > Hot Spot optimizations would become useless.
>
> >> > You can search the mailing list, you will find a couple of instructive
> >> > discussions
> >> > about this.
>
> >> > Luc P.
>
> >> > On Wed, 26 Jan 2011 10:01:04 -0800
>
> >> > Raoul Duke <rao...@gmail.com> wrote:
> >> > > On Wed, Jan 26, 2011 at 7:41 AM, Michael Gardner
> >> > > <gardne...@gmail.com> wrote:
> >> > > > However, the JVM does not support tail-call optimization.
> >> > > > Apparently Clojure can't support implicit TCO without support from
> >> > > > the JVM
>
> >> > > always wondered about that also wrt scala etc., am under the
> >> > > impression that it is implementable, but it would be too slow?
>
> >> > --
> >> > Luc P.
>
> >> > ================
> >> > The rabid Muppet
>
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