tlang-interperter-cs/tlanglib/NegativeNode.cs

namespace tlang
{
    public class NegativeNode : Node
    {
        public Node Node {get;set;}

        public NegativeNode(Node node)
        {
            this.Node = node;
        }

        public override TObject Execute(IScopeEnvironment nodeEnv)
        {
           var l = Node.Execute(nodeEnv);
          
            var lnum = l as TNumber;
            
             var dleft = l as TDictionary;

            if(dleft != null)
            {
                if(dleft.MemberExists("neg"))
                {
                    var mbm = dleft["neg"] as ICallable;
                    if(mbm != null)
                    {
                        return mbm.Call();
                    }
                }
            }

            if(lnum != null)
            return TObject.Number(-lnum.Value);

            return TObject.Null;
        }
    }
}