eval-plural.h

/* Plural expression evaluation.
   Copyright (C) 2000-2002 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
   USA.  */

#ifndef STATIC
#define STATIC static
#endif

/* Evaluate the plural expression and return an index value.  */
STATIC unsigned long int plural_eval PARAMS ((struct expression *pexp,
                                              unsigned long int n))
     internal_function;

STATIC
unsigned long int
internal_function
plural_eval (pexp, n)
     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;
}

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