The R Project SVN R

/* Plural expression evaluation.
   Copyright (C) 2000-2003 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify it
   under the terms of the GNU Library General Public License as published
   by the Free Software Foundation; either version 2, 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
   USA.  */

#ifndef STATIC
#define STATIC static
#endif

/* Evaluate the plural expression and return an index value.  */
STATIC
unsigned long int
internal_function
plural_eval (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;
}