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Procedures written in C can be registered for use from Scheme,
provided they take only arguments of type SCM
and return
SCM
values. scm_c_define_gsubr
is likely to be the most
useful mechanism, combining the process of registration
(scm_c_make_gsubr
) and definition (scm_define
).
Register a C procedure fcn as a “subr” — a primitive
subroutine that can be called from Scheme. It will be associated with
the given name but no environment binding will be created. The
arguments req, opt and rst specify the number of
required, optional and “rest” arguments respectively. The total
number of these arguments should match the actual number of arguments
to fcn, but may not exceed 10. The number of rest arguments should be 0 or 1.
scm_c_make_gsubr
returns a value of type SCM
which is a
“handle” for the procedure.
Register a C procedure fcn, as for scm_c_make_gsubr
above, and additionally create a top-level Scheme binding for the
procedure in the “current environment” using scm_define
.
scm_c_define_gsubr
returns a handle for the procedure in the
same way as scm_c_make_gsubr
, which is usually not further
required.