Crash during ciao_query_begin_term(), from C - Ciao-users

11 Jun 2003


      Hi,
What's the right way to query Ciao from C?  
Attached are two files which show what I'm trying 
(to get at some particular predicates) 
but, Ciao crashes:
Ciao-Prolog 1.9 #44: Thu May 22 22:21:28 MDT 2003
?- use_module(library(show_preds)).
yes
?- show_preds(x).
orig_var=2, ciao_is_variable? yes
goal_var=4, ciao_is_variable? yes
ciao_is_structure(goal): yes
goal is:
some_pred(_var_5)
About to begin query goal=3
{ERROR: segmentation violation}
{ Execution aborted }
?-
(To re-create the above, put the attached two files into 
your ciao library directory and follow the session as 
shown.)
- Also, I have no success getting Ciao to accept 
a 0-arity foreign predicate.  The following all fail 
with a parse error (so says assert anyway): 
:- true pred show_preds() :: foreign.
:- true pred show_preds :: foreign.
:- true pred show_preds/0 :: foreign.
(where currently I have .. show_preds(in(X)) :: ..
is that a real limit or is the syntax of the above wrong?
Thanks for any help,
Jeff
:- module(show_preds,
    [show_preds/1],
    [assertions,
     basicmodes,
     regtypes,
     foreign_interface
    ]).
%% This doesn't seem to like /0 predicates; I have tried:
%% show_preds :: ..  show_preds/0 :: .. show_preds() ::
%% So the argument is unused.
:- true pred show_preds(in(X)) :: any_term + foreign.
:- use_foreign_source(show_preds_c).
:- impl_defined([show_preds/1]).
#include <stdio.h>
#include "ciao_prolog.h"
static void print_ciao_term(ciao_term term);
void show_preds(ciao_term unused_term)
{
  ciao_term orig_var = ciao_var();
  ciao_term goal = ciao_structure("some_pred", 1, orig_var);
  ciao_term goal_var = ciao_structure_arg(goal, 1);
  ciao_query* query = 0;
printf("orig_var=%d, ciao_is_variable? %s\n", orig_var, ciao_is_variable(orig_var) ? "yes" : "no");
printf("goal_var=%d, ciao_is_variable? %s\n", goal_var, ciao_is_variable(goal_var) ? "yes" : "no");
printf("ciao_is_structure(goal): %s\n", ciao_is_structure(goal) ? "yes" : "no");
printf("goal is:\n");
print_ciao_term(goal);
printf("\n");
printf("About to begin query goal=%d\n", goal);
  query = ciao_query_begin_term(goal);
printf("Began ok...\n");
printf("First ciao_query_next query = %p\n", query);
  while (ciao_query_next(query)) {
printf("print_ciao_term(goal)\n");
    print_ciao_term(goal);
printf("\n... 'nother ciao_query_next\n");
  }
/*
ciao_bool ciao_query_ok(ciao_query *query);
ciao_bool ciao_query_next(ciao_query *query);
void ciao_query_end(ciao_query *query);
*/
  ciao_query_end(query);
}
static
void print_ciao_term(ciao_term term)
{
  if (ciao_is_atom(term)) {
    printf("%s", ciao_atom_name(term));
  } else if (ciao_is_variable(term)) {
    /* most likely not the canonical form of the var.. */
    printf("_var_%d", term);
  } else if (ciao_is_structure(term)) {
    int i;
    int a;
    a = ciao_structure_arity(term);
    printf("%s(", ciao_structure_name(term));
    for (i = 1; i <= a; i++) {
      print_ciao_term(ciao_structure_arg(term, i));
      if (i != a)
        printf(", ");
    }
    printf(")");
  } else if (ciao_is_list(term)) {
    printf("[");
    print_ciao_term(term);
    printf("]");
  } else if (ciao_is_empty_list(term)) {
    printf("[]");
  } else if (ciao_is_integer(term)) {
    printf("%d", ciao_to_integer(term));
  } else if (ciao_is_number(term)) {
    printf("%f", ciao_to_float(term));
  } else {
    printf("<unknown/>");
  }
}