[Re-added guile-devel# to CC] Stefan Israelsson Tampe schreef op zo 27-03-2022 om 16:37 [+0200]: > I mean that modul-ref is a hash-table lookup, and that's more > expensive as you say. I suggested that lexical variables should be > let bound > because you can deduce more things with them e.g. in > > (let ((a (@ x y))) > (when (vector? a) code ...)) > > Then a is known to be a vector and the check can be avoided inside > code ... > You suggest to use (@ x y) everywhere which is not terrible, > especially with wingo's recent work. But still not sure that all > optimisations work for referencing (@ x y) all the time.
I could do this, but:
* this won't work for macros, so I would have to make a special case
for them
* the imported variables might not yet have been initialised. E.g.:
(lambda ()
(use-modules/lexical (foobar))
a-foo ; initially #false
(initialise-foobar!)
a-foo) ; now 'footastic'
The problem with your proposal is that modifications to global
variables would not be detected --- the idea of 'use-modules' is to
import the _variables_, not their current _values_.
Additionally, doing the latter would be backwards-incompatible.
* not all imported variables might be used, so your proposal might
make things worse. E.g.:
(define (foo)
(use-modules (ice-9 exceptions))
(if (do-stuff)
'ok
(raise (make-some-exception with variables from (ice-9
exceptions)))))
In the normal case, the variables would not need to be dereferenced.
* I just want to make lexical use-modules work and I'm not currently
interested in (possibly futily) trying to squeezing out some extra
% or ‰ of performance.
> Would be nice though to be able to select the vars to be bound and
> improve on compilation speed if there is a lot of baggage (large
> module and only few var used)
When making a patch for merging 'use-module/lexical' into 'use-
modules', I intend to preserve support for #:select.
Greetings,
Maxime.
signature.asc
Description: This is a digitally signed message part
