Mark H Weaver writes:
> Certainly writing (a b c . #nil) as (a b c) would be most natural and
> convenient, and maybe it's the best compromise, but I'm not entirely
> sure it's safe.
>
> What if we have an association list mapping symbols to booleans that
> came from elisp? Such a alist might lo
Neil Jerram wrote:
> > One more thing: scheme code can reasonably expect to "write" a list of
> > simple values and then "read" it back in. But now, lists might be
> > terminated by %nil instead of '(). Therefore, I think "read" needs to
> > be able to read SCM_LISP_NIL in whatever form we "write
Mark H Weaver writes:
> What about scm_is_bool? I'm tempted to suggest that it should work
> the same way as "boolean?" within scheme, whatever that may be. I
> tend to think they ought to treat %nil as boolean, though I'm less
> sure of this than about scm_is_true/false/null. It's the right t
Mark H Weaver writes:
> On Sun, Aug 30, 2009 at 12:13:59PM +0100, Neil Jerram wrote:
>> Mark H Weaver writes:
>>
>> > This numbering has the nice properties that 0 is #f.
>>
>> Just to be clear: will this mean that (SCM_BOOL_F == 0) ? As things
>> stand I don't think it will, because SCM_MAKI
On Aug 31, 2009, at 17:59, Ludovic Courtès wrote:
I think I'm mildly in favor of keeping all-bits-zero as an invalid
representation. But, if it's a huge win for BDW-GC, maybe it's worth
it.
As discussed in my other message, it would actually be harmful.
Then I'm definitely in favor of keepin
Hi,
Ken Raeburn writes:
> I kind of assumed that making all-bits-zero an invalid value was a
> conscious choice by the Guile (or SCM?) designers which wasn't likely
> to be revisited. It is, after all, a fairly easy way of highlighting
> a certain class of uninitialized-value problems -- choosi
On Aug 30, 2009, at 07:13, Neil Jerram wrote:
Mark H Weaver writes:
This numbering has the nice properties that 0 is #f.
Just to be clear: will this mean that (SCM_BOOL_F == 0) ? As things
stand I don't think it will, because SCM_MAKIFLAG shifts and adds
0x04.
Just checking this because Ludovi
On Sun, Aug 30, 2009 at 12:13:59PM +0100, Neil Jerram wrote:
> Mark H Weaver writes:
>
> > This numbering has the nice properties that 0 is #f.
>
> Just to be clear: will this mean that (SCM_BOOL_F == 0) ? As things
> stand I don't think it will, because SCM_MAKIFLAG shifts and adds
> 0x04.
Ye
Neil wrote:
> > I would like to argue that the definitions of scm_is_false,
> > scm_is_true, and scm_is_null should indeed be changed to test for
> > %nil.
>
> OK, thanks to your arguments, I now agree with this.
Excellent!
What about scm_is_bool? I'm tempted to suggest that it should work
the
"Mark H. Weaver" writes:
> I found one thorny use of scm_is_bool and scm_is_null, and request
> your collective wisdom:
>
> scm_class_of() in goops.c tries to determine the class of a scheme
> value. If scm_is_bool returns true, it's classified as
> scm_class_boolean, and if scm_is_null returns
Mark H Weaver writes:
> This numbering has the nice properties that 0 is #f.
Just to be clear: will this mean that (SCM_BOOL_F == 0) ? As things
stand I don't think it will, because SCM_MAKIFLAG shifts and adds
0x04.
Just checking this because Ludovic said recently that (SCM_BOOL_F ==
0) would
Hi Mark!
Mark H Weaver writes:
> I would like to argue that the definitions of scm_is_false,
> scm_is_true, and scm_is_null should indeed be changed to test for
> %nil.
OK, thanks to your arguments, I now agree with this.
> Do a grep-find in the tree for uses of these macros. I think you'll
>
On Fri 03 Jul 2009 17:32, Mark H Weaver writes:
> It might be worth considering a build-time option to disable %nil, so
> that it's possible to build a version of guile which doesn't pay this
> price.
You probably found it, but Guile does have such an option.
(Jeez, I didn't think I'd ever find
I've discovered two more tests that can be optimized using the same
bit masking tricks: scm_is_bool and scm_is_bool_or_lisp_nil (newly
created). Since SCM_BOOL_F and SCM_BOOL_T differ by only one bit,
that one is easy. The other one can be implemented the same way
as scm_is_lisp_false in my last
Hi,
Neil Jerram writes:
> There are ways of writing compile time asserts; see
> http://www.jaggersoft.com/pubs/CVu11_3.html for some. I don't know
> how portable these all are, but at work we use the case label one, and
> that seems to be good on common platforms.
Gnulib's `verify' module prov
Having thought more about optimizing %nil handling, it occurs to me
that we will also want boolean tests from within lisp to be optimized.
>From lisp, three values are considered to be false: #f, '(), and %nil.
We can use the same bit-masking trick to do these tests quickly if we
make sure that th
On Mon, Jul 06, 2009 at 10:46:11PM +0100, Neil Jerram wrote:
> Assuming you are planning to work on the code changes for this, we
> will need copyright assignment papers from you. Will that be OK?
Yes, certainly. I live in the Boston area, so I'll stop by the FSF
office and take care of that soo
Mark H Weaver writes:
> Below is a proposal for how to make boolean tests and end-of-list
> tests faster and more compact, by renumbering the representations for
> SCM_ELISP_NIL, SCM_EOL, SCM_UNDEFINED, and SCM_EOF_VAL.
Interesting. I haven't looked at every detail but I'm happy to go
along wit
I would like to argue that the definitions of scm_is_false,
scm_is_true, and scm_is_null should indeed be changed to test for
%nil.
Do a grep-find in the tree for uses of these macros. I think you'll
find that the majority of places where they are used should also be
checking for %nil, but they a
On Sun 05 Jul 2009 03:41, Mark H Weaver writes:
> Below is a proposal for how to make boolean tests and end-of-list
> tests faster and more compact, by renumbering the representations for
> SCM_ELISP_NIL, SCM_EOL, SCM_UNDEFINED, and SCM_EOF_VAL.
That looks like great work, Mark!!
I don't think
Below is a proposal for how to make boolean tests and end-of-list
tests faster and more compact, by renumbering the representations for
SCM_ELISP_NIL, SCM_EOL, SCM_UNDEFINED, and SCM_EOF_VAL.
But first, I decided to quantify the increase in code size testing
against two constants instead of one, b
Thank you, Neil, for the pointers to earlier discussions of this
subject. Having read them, I've been convinced that the %nil approach
is reasonable and probably the best way to deal with elisp<->scheme
interoperability. Though, like you, I was not willing to easily
accept two false values and tw
Mark H Weaver writes:
> I've been considering writing a python compiler for guile.
Great!
> For python
> (and others) there are several values considered to be false, such as
> 0 and various empty collections, and so a different approach will have
> to be taken to this problem.
>
> If we want
Hi,
Mark H Weaver writes:
> I've been considering writing a python compiler for guile. For python
> (and others) there are several values considered to be false, such as
> 0 and various empty collections, and so a different approach will have
> to be taken to this problem.
[...]
> So how abou
I've been considering writing a python compiler for guile. For python
(and others) there are several values considered to be false, such as
0 and various empty collections, and so a different approach will have
to be taken to this problem.
If we want guile to handle many different languages, shou
Daniel Kraft writes:
> it seems so. Doing just a
>
> scheme@(guile-user)> (if %nil 1 2)
> 1
>
> with a recent build (of at least my elisp branch, but that did not
> change anything in this respect of course) gives that answer.
>
> Doing ,o interp #t as Andy did however also gives the right answe
Hi Neil,
Neil Jerram wrote:
Andy Wingo writes:
Guile has treated %nil as false for quite some time:
scheme@(guile-user)> ,o interp #t
scheme@(guile-user)> (if %nil 1 2)
$1 = 2
I'm sorry... you're completely right. Brain storm on my part.
But then I don't understand the cause o
Andy Wingo writes:
> On Mon 29 Jun 2009 23:44, Neil Jerram writes:
>
>> Andy Wingo writes:
>>
>>> scheme@(guile-user)> (if %nil 1 2)
>>> 1
>>>
>>> #define scm_is_false(x) (scm_is_eq ((x), SCM_BOOL_F) || SCM_NILP (x))
>
>> Seems wrong to me. In Scheme #f should be the only false val
On Mon 29 Jun 2009 23:44, Neil Jerram writes:
> Andy Wingo writes:
>
>> scheme@(guile-user)> (if %nil 1 2)
>> 1
>>
>> #define scm_is_false(x) (scm_is_eq ((x), SCM_BOOL_F) || SCM_NILP (x))
> Seems wrong to me. In Scheme #f should be the only false value.
> What's the argument for %n
Andy Wingo writes:
> Hi all,
>
> Daniel came up with an interesting test case:
>
> scheme@(guile-user)> (if %nil 1 2)
> 1
>
> We could fix this transparently by changing scm_is_false in boolean.h
> from:
>
> #define scm_is_false(x) scm_is_eq ((x), SCM_BOOL_F)
>
> to
>
> #define sc
Hi all,
Daniel came up with an interesting test case:
scheme@(guile-user)> (if %nil 1 2)
1
We could fix this transparently by changing scm_is_false in boolean.h
from:
#define scm_is_false(x) scm_is_eq ((x), SCM_BOOL_F)
to
#define scm_is_false(x) (scm_is_eq ((x), SCM_BOOL_F) ||
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