1/* Plural expression evaluation.
2   Copyright (C) 2000-2003 Free Software Foundation, Inc.
3
4   This program is free software; you can redistribute it and/or modify it
5   under the terms of the GNU Library General Public License as published
6   by the Free Software Foundation; either version 2, or (at your option)
7   any later version.
8
9   This program is distributed in the hope that it will be useful,
10   but WITHOUT ANY WARRANTY; without even the implied warranty of
11   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
12   Library General Public License for more details.
13
14   You should have received a copy of the GNU Library General Public
15   License along with this program; if not, write to the Free Software
16   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
17   USA.  */
18
19#ifndef STATIC
20#define STATIC static
21#endif
22
23/* Evaluate the plural expression and return an index value.  */
24STATIC
25unsigned long int
26internal_function
27plural_eval (struct expression *pexp, unsigned long int n)
28{
29  switch (pexp->nargs)
30    {
31    case 0:
32      switch (pexp->operation)
33	{
34	case var:
35	  return n;
36	case num:
37	  return pexp->val.num;
38	default:
39	  break;
40	}
41      /* NOTREACHED */
42      break;
43    case 1:
44      {
45	/* pexp->operation must be lnot.  */
46	unsigned long int arg = plural_eval (pexp->val.args[0], n);
47	return ! arg;
48      }
49    case 2:
50      {
51	unsigned long int leftarg = plural_eval (pexp->val.args[0], n);
52	if (pexp->operation == lor)
53	  return leftarg || plural_eval (pexp->val.args[1], n);
54	else if (pexp->operation == land)
55	  return leftarg && plural_eval (pexp->val.args[1], n);
56	else
57	  {
58	    unsigned long int rightarg = plural_eval (pexp->val.args[1], n);
59
60	    switch (pexp->operation)
61	      {
62	      case mult:
63		return leftarg * rightarg;
64	      case divide:
65#if !INTDIV0_RAISES_SIGFPE
66		if (rightarg == 0)
67		  raise (SIGFPE);
68#endif
69		return leftarg / rightarg;
70	      case module:
71#if !INTDIV0_RAISES_SIGFPE
72		if (rightarg == 0)
73		  raise (SIGFPE);
74#endif
75		return leftarg % rightarg;
76	      case plus:
77		return leftarg + rightarg;
78	      case minus:
79		return leftarg - rightarg;
80	      case less_than:
81		return leftarg < rightarg;
82	      case greater_than:
83		return leftarg > rightarg;
84	      case less_or_equal:
85		return leftarg <= rightarg;
86	      case greater_or_equal:
87		return leftarg >= rightarg;
88	      case equal:
89		return leftarg == rightarg;
90	      case not_equal:
91		return leftarg != rightarg;
92	      default:
93		break;
94	      }
95	  }
96	/* NOTREACHED */
97	break;
98      }
99    case 3:
100      {
101	/* pexp->operation must be qmop.  */
102	unsigned long int boolarg = plural_eval (pexp->val.args[0], n);
103	return plural_eval (pexp->val.args[boolarg ? 1 : 2], n);
104      }
105    }
106  /* NOTREACHED */
107  return 0;
108}
109