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LogicFunctionSet.cs

//
// LogicFunctionSet.cs
//
// Author:
//   Aaron Bockover <abockover@novell.com>
//
// Copyright (C) 2007-2008 Novell, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

using System;

namespace Hyena.SExpEngine
{
    public class LogicFunctionSet : FunctionSet
    {
        [Function("not", "!")]
        public virtual TreeNode OnNot(TreeNode [] args)
        {
            if(args.Length != 1) {
                throw new ArgumentException("not must have only one argument");
            }

            TreeNode arg = Evaluate(args[0]);

            if(!(arg is BooleanLiteral)) {
                throw new ArgumentException("can only not a boolean");
            }

            return new BooleanLiteral(!(arg as BooleanLiteral).Value);
        }

        [Function("or", "|")]
        public virtual TreeNode OnOr(TreeNode [] args)
        {
            return OnAndOr(args, false);
        }

        [Function("and", "|")]
        public virtual TreeNode OnAnd(TreeNode [] args)
        {
            return OnAndOr(args, true);
        }

        private TreeNode OnAndOr(TreeNode [] args, bool and)
        {
            if(args.Length < 2) {
                throw new ArgumentException("must have two or more boolean arguments");
            }

            bool result = false;

            for(int i = 0; i < args.Length; i++) {
                TreeNode node = Evaluate(args[i]);
                if(!(node is BooleanLiteral)) {
                    throw new ArgumentException("arguments must be boolean");
                }

                BooleanLiteral arg = (BooleanLiteral)node;

                if(i == 0) {
                    result = arg.Value;
                    continue;
                }

                if(and) {
                    result &= arg.Value;
                } else {
                    result |= arg.Value;
                }
            }

            return new BooleanLiteral(result);
        }
    }
}

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