---------- Forwarded message --------- From: Stefan Israelsson Tampe <stefan.ita...@gmail.com> Date: Tue, Jan 14, 2020 at 12:43 PM Subject: Re: GNU Guile 2.9.9 Released [beta] To: Andy Wingo <wi...@pobox.com>
Thanks! Phew! I think that for an f, a direct function application need not to be counted as a position. Only when you use f in a higher order manner demands that you count this. E.g. (g f), (return f) Regards Stefan On Tue, Jan 14, 2020 at 12:16 PM Andy Wingo <wi...@pobox.com> wrote: > On Mon 13 Jan 2020 22:32, Stefan Israelsson Tampe <stefan.ita...@gmail.com> > writes: > > > In current guile (eq? f f) = #f for a procedure f. Try: > > Note that procedure equality is explicitly unspecified by R6RS. Guile's > declarative modules optimization took advantage of this to eta-expand > references to declaratively-bound top-level lambda expressions. This > unlocks the "well-known" closure optimizations: closure elision, > contification, and so on. > > However, the intention with the eta expansion was really to prevent the > > (module-add! mod 'foo foo) > > from making the procedure not-well-known. If that's the only reference > to `foo' outside the operator position, procedure identity for `foo' is > kept, because it's only accessed outside the module. But then I > realized thanks to your mail (and the three or four times that people > stumbled against this beforehand) that we can preserve the optimizations > and peoples' intuitions about procedure equality if we restrict > eta-expansion to those procedures that are only referenced by value in > at most a single position. > > It would be best to implement the eta-expansion after peval; doing it > where we do leaves some optimization opportunities on the table. But I > have implemented this change in git and it should fix this issue. > > Comparative benchmark results: > > > https://wingolog.org/pub/guile-2.9.7-vs-guile-2.9.9-with-eq-change-microbenchmarks.png > > Regards, > > Andy >
