Trying to make a generic VC++ function...

[Joseph N. Fiore]

Forgive my ignorance as I'm very new to GNU-Prolog and prolog in
general.  

I'm trying to make a very generic VC++ function to call Prolog
functions.
It works with the new_main.pl example, ie when there are only two terms
to the function.  But it doesn't work with three terms.

I want to call:  plSolve("triple", "?X,bb,cc");
and it returns "aa,cc,dd;bb,cc,dd"

/* the Prolog file */
triple(aa,cc,dd).
triple(bb,cc,dd).
triple(cc,dd,ee).
triple(cc,bb,ee).


The problem is the call Rd_String(arg[i]).  It segvaults whenever it
reaches a returned term that was a variable.  Since I don't have a
version of the libraries compiled with debug, I can't trace into the
Rd_String call.

Any help would be greatly appreciated.  I probably don't understand half
the GNU-Prolog functions even though I've been through the code quite a
bit.
Also: sorry for the largish code example but I removed as much as I
could

  --Joe



// chaArgs:  "aa,bb,?X,"
PROLOGINF_API char *plSolve(string chrPredicate, chrArgs)
{
   WamWord   arg[20];
   
   // vectorize the chrArgs
   // turn chrArgs "?X,?Y,bob" into a vector of three strings
vecArguments
   plTokenize(chrArgs, ",", vecArguments);

   // fill arg with vecArguments
   // foreach iterArguments in vecArguments
   int cntArguments = 0;
   for (iterArguments = vecArguments.begin();
        iterArguments != vecArguments.end();
        iterArguments++)
   {
      // Process Variable
      if (it starts with '?') { 
         arg[cntArguments] = Mk_Variable(); 
      }
      // Process constant
      else { 
         arg[cntArguments] = Mk_String((char*)(*iterArguments).c_str());
      }
      cntArguments++;
   }
   
   int FindHandle = Find_Atom(chrPredicate);
   Pl_Query_Begin(TRUE);

   string retval = "";
   int cntSolution = 0;

   // Get first results
   int Results = Pl_Query_Call(FindHandle, cntArguments, arg);

   // While there are results to process
    while (Results) {
      // not first solution: append ";"
      if (cntSolution) retval += ";";
      cntSolution++;
      
      // for all the returned arguments
      for (int i = 0;   i < cntArguments; i++)
      {
         // not first returned argument: append ","
         if (i) retval += ",";
         retval += Rd_String(arg[i]);
      }

      Results   = Pl_Query_Next_Solution();
      DBG(DARG,"Results: %d\n", Results);
   }
   
   Pl_Query_End(PL_RECOVER);
   
   plResults = strdup(retval.c_str());
   return plResults;
}