/* Plural expression evaluation.

   Copyright (C) 2000-2018 Free Software Foundation, Inc.

   This program is free software: you can redistribute it and/or modify

   it under the terms of the GNU Lesser General Public License as published by

   the Free Software Foundation; either version 2.1 of the License, or

   (at your option) any later version.

   This program is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

   GNU Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License

   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#ifndef STATIC

#define STATIC static

#endif

/* Evaluate the plural expression and return an index value.  */

STATIC

unsigned long int

plural_eval (const struct expression *pexp, unsigned long int n)

{

  switch (pexp->nargs)

    {

    case 0:

      switch (pexp->operation)

	{

	case var:

	  return n;

	case num:

	  return pexp->val.num;

	default:

	  break;

	}

      /* NOTREACHED */

      break;

    case 1:

      {

	/* pexp->operation must be lnot.  */

	unsigned long int arg = plural_eval (pexp->val.args[0], n);

	return ! arg;

      }

    case 2:

      {

	unsigned long int leftarg = plural_eval (pexp->val.args[0], n);

	if (pexp->operation == lor)

	  return leftarg || plural_eval (pexp->val.args[1], n);

	else if (pexp->operation == land)

	  return leftarg && plural_eval (pexp->val.args[1], n);

	else

	  {

	    unsigned long int rightarg = plural_eval (pexp->val.args[1], n);

	    switch (pexp->operation)

	      {

	      case mult:

		return leftarg * rightarg;

	      case divide:

#if !INTDIV0_RAISES_SIGFPE

		if (rightarg == 0)

		  raise (SIGFPE);

#endif

		return leftarg / rightarg;

	      case module:

#if !INTDIV0_RAISES_SIGFPE

		if (rightarg == 0)

		  raise (SIGFPE);

#endif

		return leftarg % rightarg;

	      case plus:

		return leftarg + rightarg;

	      case minus:

		return leftarg - rightarg;

	      case less_than:

		return leftarg < rightarg;

	      case greater_than:

		return leftarg > rightarg;

	      case less_or_equal:

		return leftarg <= rightarg;

	      case greater_or_equal:

		return leftarg >= rightarg;

	      case equal:

		return leftarg == rightarg;

	      case not_equal:

		return leftarg != rightarg;

	      default:

		break;

	      }

	  }

	/* NOTREACHED */

	break;

      }

    case 3:

      {

	/* pexp->operation must be qmop.  */

	unsigned long int boolarg = plural_eval (pexp->val.args[0], n);

	return plural_eval (pexp->val.args[boolarg ? 1 : 2], n);

      }

    }

  /* NOTREACHED */

  return 0;

}