guile program scanning integers

filter.c

#include <stdio.h>
#include <libguile.h>


struct Global {
    /** inputstream */
    FILE* in;
    /** currrent value */
    int value;
    /** contains script as string */
    char buffer[2048];
    };

static struct Global global;

/** retrieve the next record, return #t on success */
static SCM _next () {
  int ret = fscanf(global.in,"%d", &(global.value));
  if(ret!=1) return SCM_BOOL_F;
  return SCM_BOOL_T;
}
/** get current number */
static SCM _get () {
  return scm_from_int(global.value);
}

/** output current number */
static SCM _emit () {
  fprintf(stderr,"%d\n",global.value);
  return SCM_BOOL_T;
}

/** dispose memory associated */
static SCM _dispose () {
  return SCM_BOOL_T;
}


static void*
inner_main (void *data)
{
    struct Global* g= (struct Global*)data;
    scm_c_define_gsubr("_next", 0, 0, 0, _next);
    scm_c_define_gsubr("_get", 0, 0, 0, _get);
    scm_c_define_gsubr("_emit", 0, 0, 0, _emit);
    scm_c_define_gsubr("_dispose", 0, 0, 0, _dispose);
    scm_c_eval_string(g->buffer);
    return 0;
}

int main(int argc,char** argv) {
    if(argc!=2) return -1;
    global.value=1;
    global.in = stdin;
    sprintf(global.buffer,"(while (_next) (if %s  (_emit)   ) (_dispose) )  ",argv[1]);
    scm_with_guile(inner_main,(void*)&global);
    return 0;
    }

Makefile

GUILE_VERSION=2.2
# Tell the C compiler where to find <libguile.h>
CFLAGS=`pkg-config --cflags guile-$(GUILE_VERSION)`

# Tell the linker what libraries to use and where to find them.
LIBS=`pkg-config --libs guile-$(GUILE_VERSION)`


test: a.out
	seq 1 100 | ./a.out '(= (modulo (_get) 7) 0)'
a.out: filter.c
	$(CC) $(CFLAGS) -o $@ $< $(LIBS)