(function (tree) {

tree.Condition = function (op, l, r, i, negate) {
    this.op = op.trim();
    this.lvalue = l;
    this.rvalue = r;
    this.index = i;
    this.negate = negate;
};
tree.Condition.prototype.eval = function (env) {
    var a = this.lvalue.eval(env),
        b = this.rvalue.eval(env);

    var i = this.index, result;

    var result = (function (op) {
        switch (op) {
            case 'and':
                return a && b;
            case 'or':
                return a || b;
            default:
                if (a.compare) {
                    result = a.compare(b);
                } else if (b.compare) {
                    result = b.compare(a);
                } else {
                    throw { type: "Type",
                            message: "Unable to perform comparison",
                            index: i };
                }
                switch (result) {
                    case -1: return op === '<' || op === '=<';
                    case  0: return op === '=' || op === '>=' || op === '=<';
                    case  1: return op === '>' || op === '>=';
                }
        }
    })(this.op);
    return this.negate ? !result : result;
};

})(require('../tree'));