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Michael Livshin 2000-09-12 18:18:39 +00:00
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[This is currently a collection of information in an unedited state.
Someone will change this soon.]
The C names for Scheme primitives *always* obey a fixed name
translation scheme:
scm_XXX where XXX is translated from the Scheme name, except that
- becomes _
! becomes _x
? becomes _p
% becomes sys_
If there's a C variant of something provided at the Scheme level (like
the current scm_internal_dynamic_wind), it has the prefix scm_c_
instead of scm_.
A function named scm_c_FOO serves the same purpose as the function
named scm_FOO, except that its interface is tailored for use from C,
while scm_FOO is tailored for use from Scheme, and is probably
exported as a Scheme primitive.
For example, scm_FOO might expect Scheme procedures as arguments,
while scm_c_FOO might take C function pointers and a passthrough
value.
If there's a C function with global scope which is only intended to be
used internally in libguile, it has the prefix scm_i_.
String literals with global scope has the prefix scm_s_. (Greg
introduced the prefix s_scm_ but this has to change to scm_s_ since
s_scm_ trespasses the user's namespace.)
Not correct: Those names have module-local scope and does not trespass
user name space.
Keywords with global scope has the prefix scm_k_.
Symbols with global scope has the prefix scm_sym_.
Variable bindings with global scope has the prefix scm_var_.
Names, in general, have an internal left-to-right order of increasing
specificity: scm_ is least specific. It is often followed by some
type, like `stack', and, finally, the operation. Example:
scm_stack_length.
There are exceptions, though:
* If a name is already established at the Scheme level, this defines
the C name through the translation scheme.
* According to the rule, we should have `SCM_SMOB_DATA_SET', but we
instead have `SCM_SET_SMOB_DATA'. Generally, `set' should be placed
as far left as possible:
`port-filename' scm_port_filename
`set-port-filename!' scm_set_port_filename_x
SCM_SMOB_DATA
SCM_SET_SMOB_DATA
* Guile has a lot of history with lots of different strange names.
Perhaps a major name overhaul can be done at the same time as we go
through Guile's interfaces to checks soundness and theoretical
properties such as type safety. We *should* be a bit careful with
name changes in order not to break existing application code.
> Further, I'd love it if macros to create scheme values from C values would
> be named SCM_MAKE_... more consitently. Currently, we have SCM_MAKICHAR
> (OK, this one's been made deprecated), SCM_MAKINUM and others.
I agree.
> Also, some macros are used for symbols or keywords. The best solution
> would be to use a similar naming scheme for these also.
>
> It's good to talk about improving guile's API. A clean, consistent and
> beautiful api is, in my belief, important for guile's attractivity, and
> makes learning it easier.
Yes!
There are still some open points:
scm_c_XXX :
Only used for C-level variants of a scm_XXX schene primitive, or
rather to be used for everything that is not a scheme primitive?
scm_i_XXX :
Only for internal _functions_ or rather for everything that is
internal? For example, scm_sym_ is for symbols that may be used by
users, while scm_i_sym_ is used for guile internally? Otherwise we
can't distinguish between C variables holding symbols that are part of
the official API and internally used C variables holding symbols.
what about boolean variables/constants? scm_bool_? This would fit nicely
with the current macro names SCM_BOOL_T and SCM_BOOL_F.
what about number variables/constants? scm_num_? There is at least a
SCM_MAKINUM(0) somewhere...
scm_s_, scm_k_, scm_sym_, scm_var_:
What about macro variants of these? At least, some symbols and
constants are represented as macros.
Macros in general:
Should internally used macros be called SCM_I_xxx, thus following the
above scheme?
How do scheme-level names translate if there are macros that do the
same thing? set-car! --> SCM_SETCAR, thus, the '!' is dropped and the
intermediate '-' is dropped. However, this is not done
consistently: sometimes intermediate '-' are _not_ dropped.
Currently it seem that:
- becomes sometimes _ and sometimes nothing
! becomes nothing
? becomes P for single-word xxx, _P otherwise
% becomes I don't know what.
I would prefer if both worlds (functions/variables and macros) were using
similar schemes as far as possible. (I even dislike the _P/P
distinction, but I know that I am strange :-)