/* Raise BASE to the EXPO power, reduced modulo MOD.  The result is
  

  placed in RESULT.  If a EXPO is not an integer,
  

  only the integer part is used.  */
  

  int
  

  bc_raisemod (bc_num base, bc_num expo, bc_num mod, bc_num *result, int scale TSRMLS_DC)
  

  {
  

  bc_num power, exponent, parity, temp;
  

  int rscale;
  

  

  /* Check for correct numbers. */
  

  if (bc_is_zero(mod TSRMLS_CC)) return -1;
  

  if (bc_is_neg(expo)) return -1;
  

  

  /* Set initial values.  */
  

  power = bc_copy_num (base);
  

  exponent = bc_copy_num (expo);
  

  temp = bc_copy_num (BCG(_one_));
  

  bc_init_num(&parity TSRMLS_CC);
  

  

  /* Check the base for scale digits. */
  

  if (base->n_scale != 0)
  

  <coding-2 lang="other">
  

  bc_rt_warn ("non-zero scale in base");
  

  /* Check the exponent for scale digits. */
  

  if (exponent->n_scale != 0)
  

  {
  

  bc_rt_warn ("non-zero scale in exponent");
  

  bc_divide (exponent, BCG(_one_), &exponent, 0 TSRMLS_CC); /*truncate */
  

  }
  

  /* Check the modulus for scale digits. */
  

  if (mod->n_scale != 0)
  

  bc_rt_warn ("non-zero scale in modulus");
  

  /* Do the calculation. */
  

  rscale = MAX(scale, base->n_scale);
  

  while ( !bc_is_zero(exponent TSRMLS_CC) )
  

  {
  

  (void) bc_divmod (exponent, BCG(_two_), &exponent, &parity, 0 TSRMLS_CC);
  

  if ( !bc_is_zero(parity TSRMLS_CC) )
  

  {
  

  bc_multiply (temp, power, &temp, rscale TSRMLS_CC);
  

  (void) bc_modulo (temp, mod, &temp, scale TSRMLS_CC);
  

  }
  

  

  bc_multiply (power, power, &power, rscale TSRMLS_CC);
  

  (void) bc_modulo (power, mod, &power, scale TSRMLS_CC);
  

  }
  

  

  /* Assign the value  */
  

  bc_free_num (&power);
  

  bc_free_num (&exponent);
  

  bc_free_num (result);
  

  bc_free_num (&parity);
  

  *result = temp;
  

  return 0; /* Everything is OK. */
  

  }