/*************************************************************
 *
 * This is an implementation of a predicate in C++.
 * Multiple values are returned in a pipelined fashion.
 * This function, given a string, returns each character and
 * its position at a time. On each success, LDL_SUCCESS is 
 * returned. LDL_FAIL is returned upon a failure. A local
 * state variable, State, maintains the state of the
 * computation between invocations.
 *
 * Note: This function is re-entrant, as all LDL++ externals
 *	 ought to be.
 *
 **************************************************************/

#include <ldl_extern.h>
#include <string.h>
#include <stream.h>
#include <stdio.h>

// Make sure that the name is not mangled
extern "C"
{
  LdlStatus all_letters(LdlObject str, LdlObject ch,
			LdlObject pos);
}

// State variables
typedef struct
{
  int	position;		// Current position
  int	length;			// Length of string
} State;


LdlStatus all_letters(LdlObject str, LdlObject ch,
		      LdlObject pos)
{
  State*	state;
  LdlStatus	status;
  char		ret_string[2];
  char*		c_string;

  if (ldl_entry_p())
    {
      // This is the first time around
      // Create the state structure
      state = (State *)ldl_create_state(sizeof(State));

      // Initialize the position
      state->position = 0;

      if (c_string = ldl_get_string(str))
	state->length = strlen(c_string);
      else
	state->length = 0;
    }

  // Recover the state from the LDL++ system
  state = (State *)ldl_get_state();
  
  if ((c_string = ldl_get_string(str)) &&
      (state->position < state->length))
    {
      LdlObject	temp_string;
      LdlObject	temp_int;

      ret_string[0] = c_string[state->position];
      ret_string[1] = '\0';

      temp_string = ldl_create_string(ret_string);
      temp_int = ldl_create_int(state->position);

      ldl_assign_argument(ch, temp_string);
      ldl_assign_argument(pos, temp_int);
      state->position++;

      ldl_delete_object(temp_string);
      ldl_delete_object(temp_int);

      status = LDL_SUCCESS;
    }
  else
    status = LDL_FAIL;

  return(status);
}