2009/8/2 Richard Shann <richard.sh...@virgin.net>:
> Hi,
> I want to call a scheme procedure with four arguments from C.
> (The example scheme procedure here is just displaying its arguments.)
>
> (define (d-UploadRoutine a b c d)
> (display a)
> (display b)
> (display c)
> (display d))
>
> But I can't find what the correct parameters types are -
guile is not typed, or rather, is typed at runtime only, or dynamically typed.
> the headers
> just say SCM, here are three things that give errors, two commented out
>
>
> SCM proc = gh_str2scm("d-UploadRoutine", strlen("d-UploadRoutine"));
The gh_* routines are old and deprecated, and have been for about
a decade now .. don't use them.
On the other hand, I notice that the tutorial at
http://www.gnu.org/software/guile/docs/docs.html
still uses gh_, so clearly, the gnu docs need cleanup :-(
> // proc = scm_string_to_symbol("d-UploadRoutine");
> // proc = scm_string_to_symbol( gh_str2scm("d-UploadRoutine",
> strlen("d-UploadRoutine")));
> SCM arg1 = gh_str2scm("hello", strlen("hello"));
> SCM arg2 = gh_str2scm("he2lo", strlen("hello"));
> SCM arg3 = gh_str2scm("he3lo", strlen("hello"));
> SCM arg4 = gh_str2scm("he4lo", strlen("hello"));
> scm_call_4(proc, arg1, arg2, arg3, arg4);
>
> The three definitions of proc lead to the following three error messages:
>
> ERROR: In procedure apply:
> ERROR: Wrong type argument in position 1: "d-UploadRoutine"
google suggests that you read
http://www.lonelycactus.com/guilebook/x220.html
and
http://lonelycactus.com/guilebook/c1204.html
which I think is a start, and should get you going.
There's more stuff in
http://www.gnu.org/software/guile/manual/html_node/Programming-in-C.html
but it lacks examples.
> It seems to me the docs are rather deficient here!
The examples are particularly so.
> They don't give the types of the
> arguments, and the header only tells you they are SCM...
scheme is like perl, in that the types are determined during
runtime. This is considered to be a "strength", in that, in principle,
you can define a routine that does the "right thing" for any type.
--linas
