>> The reason is accessing macros from languages
>> other than C is cumbersome.
>
> Apologies for ignoring you.
Hi, Wingo, Hi, All,
No need to apologise, given your track record I trust you spending
every minute of your time for a good purpose. :)
Lack of time is a good evolutionary filter against worthless proposals.
> I think that the thought that if we wanted
> to follow through the logic of making Guile's C API available to non-C
> languages, we should do so either all the way or not at all.
This does not need to be a full Guile API, but rather a "Scheme"
API --- the necessary minimum to "write Scheme in a foreign language".
A language may be assumed to be C-interoperable, though macros should
not be part of this interoperability.
> Each additional function added to Guile's ABI imposes additional cost in
> runtime memory, ELF symbol resolution, and (to a degree) startup time,
> without providing any benefits to C users. On the other hand, if we are
> only talking about 2 functions (say), then clearly we should do it. So
> part of the question is, how much work are we talking about?
Another valid reason to distinguish Guile and "Scheme" APIs.
> I grepped the header files for lines starting with "#define SCM_",
> munged out the name of the macro and sorted them for uniqueness. That
> was around 1200 macros. I filtered out certain kinds of macros:
>
> * those ending in _H (header guards)
> * those starting with SCM_I_ (internal macros)
> * those containing _BIT (implementation details)
> * SCM_VALIDATE_ macros (there are corresponding C procedures)
>
> That left me with about 900 macros.
>
> I then filtered out all macros that had a corresponding C binding. For
> example, SCM_CAR has a C procedure, `scm_car'. That left me with about
> 780 macros.
>
> Finally, from this list, I filtered out those symbols that did not
> appear in our documentation. That resulted in the following 77 symbols:
Thanks for a serious analysis. However there appear also to be some lower
case scm_* macros documented as an API. Here are those that I had to
"add to API as functions" in my case:
scm_to_int();
scm_is_true();
scm_is_symbol();
scm_is_null();
These may be the real showstoppers. Someone on the list (or IRC) told
me adding them as functions may result in a problem. Or was that
"redefining them as functions"?
I must confess that I never compiled Guile myself, so I am in no way
qualified ehough to classify all the SCM_* macros left after your filtering,
but let me start.
The first group of a few constants contains those that are mentioned in
the Scheme standard. Most of them may be obtained as a return value by
calling that or another function. A global (linker) symbol or a
dedicated "constructor" may be more convinient in some situations for
foreign bindings:
SCM_BOOL_F #f
SCM_BOOL_T #t
SCM_EOL '()
SCM_UNDEFINED "something that when stored in a location
makes it an error to try to obtain the value
stored in the location (no such expression is
defined in Scheme)"
SCM_UNSPECIFIED (if #f #f)
SCM_EOF_VAL (with-input-from-string "" read)
Not so sure about the next two predicates. They do not have a Scheme
counterpart, but appear to be an important implementation detail for
functions of variable arity (I guess). There appears to be already
some redundancy/confusion, at least for me [1]:
SCM_UNBNDP
SCM_UNBOUND
The rest below should not be required to "write scheme in a foreign
language", but rather to extend Scheme. Other macros, such as
SCM_GLOBAL_VARIABLE_INIT, and snarfing magic are convenience macros
for C programs and do not necessarily need to have a counterpart in
other bindings:
SCM_ALLOW_INTS
SCM_ARG1
SCM_ARG2
SCM_ARG3
SCM_ARG4
SCM_ARG5
SCM_ARG6
SCM_ARG7
SCM_ARGn
SCM_ASSERT_TYPE
SCM_BYTEVECTOR_CONTENTS
SCM_CELL_OBJECT
SCM_CELL_OBJECT_0
SCM_CELL_OBJECT_1
SCM_CELL_TYPE
SCM_CELL_WORD
SCM_CELL_WORD_0
SCM_CELL_WORD_1
SCM_DEFER_INTS
SCM_ELISP_NIL
SCM_FRAME_DATA_ADDRESS
SCM_FRAME_LOWER_ADDRESS
SCM_FRAME_UPPER_ADDRESS
SCM_GLOBAL_KEYWORD
SCM_GLOBAL_VARIABLE
SCM_GLOBAL_VARIABLE_INIT
SCM_GPROC
SCM_HOOKP
SCM_IMP
SCM_NEWSMOB
SCM_NEWSMOB2
SCM_NEWSMOB3
SCM_PTAB_ENTRY
SCM_PTOBNUM
SCM_REGISTER_PROC
SCM_RETURN_NEWSMOB
SCM_RETURN_NEWSMOB2
SCM_RETURN_NEWSMOB3
SCM_SET_CELL_OBJECT
SCM_SET_CELL_OBJECT_0
SCM_SET_CELL_OBJECT_1
SCM_SET_CELL_TYPE
SCM_SET_CELL_WORD
SCM_SET_CELL_WORD_0
SCM_SET_CELL_WORD_1
SCM_SET_SMOB_DATA
SCM_SET_SMOB_DATA_2
SCM_SET_SMOB_DATA_3
SCM_SET_SMOB_FLAGS
SCM_SET_SMOB_OBJECT
SCM_SET_SMOB_OBJECT_2
SCM_SET_SMOB_OBJECT_3
SCM_SIMPLE_VECTOR_LENGTH
SCM_SIMPLE_VECTOR_REF
SCM_SIMPLE_VECTOR_SET
SCM_SMOB_DATA
SCM_SMOB_DATA_2
SCM_SMOB_DATA_3
SCM_SMOB_FLAGS
SCM_SMOB_OBJECT
SCM_SMOB_OBJECT_2
SCM_SMOB_OBJECT_2_LOC
SCM_SMOB_OBJECT_3
SCM_SMOB_OBJECT_3_LOC
SCM_SMOB_OBJECT_LOC
SCM_SMOB_PREDICATE
SCM_TICK
SCM_VARIABLE_INIT
Alexei
[1] http://www.sourceware.org/ml/guile/2000-03/msg00618.html
