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• Does "delegate" mean a type or an object?

  - by Michal Czardybon

  Reading from MSDN: "A delegate is a type that references a method. Once a delegate is assigned a method, it behaves exactly like that method." Does then "delegate" mean a type or an object?! ...It cannot be both. It seems to me that the single word is used in two different meanings: a type containing a reference to a method of some specified signature, an object of that type, which can be actually called like a method. I would prefer a more precise vocabulary and use "delegate type" for the first case. I have been recently reading a lot about events and delegates and that ambiguity was making me confused many times. Some other uses of "delegate" word in MSDN in the first meaning: "Custom event delegates are needed only when an event generates event data" "A delegate declaration defines a class that is derived from the class System.Delegate" Some other uses of "delegate" word in MSDN in the second meaning: "specify a delegate that will be called upon the occurrence of some event" "Delegates are objects that refer to methods. They are sometimes described as type-safe function pointers" What do you think? Why did people from Microsoft introduced this ambiguity? Am I the only person to have conceptual problems with different notions being referenced with the same word.

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• Are there equivalents to Ruby's method_missing in other languages?

  - by Justin Ethier

  In Ruby, objects have a handy method called method_missing which allows one to handle method calls for methods that have not even been (explicitly) defined: Invoked by Ruby when obj is sent a message it cannot handle. symbol is the symbol for the method called, and args are any arguments that were passed to it. By default, the interpreter raises an error when this method is called. However, it is possible to override the method to provide more dynamic behavior. The example below creates a class Roman, which responds to methods with names consisting of roman numerals, returning the corresponding integer values. class Roman def romanToInt(str) # ... end def method_missing(methId) str = methId.id2name romanToInt(str) end end r = Roman.new r.iv #=> 4 r.xxiii #=> 23 r.mm #=> 2000 For example, Ruby on Rails uses this to allow calls to methods such as find_by_my_column_name. My question is, what other languages support an equivalent to method_missing, and how do you implement the equivalent in your code?

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• using Python reduce over a list of pairs

  - by user248237

  I'm trying to pair together a bunch of elements in a list to create a final object, in a way that's analogous to making a sum of objects. I'm trying to use a simple variation on reduce where you consider a list of pairs rather than a flat list to do this. I want to do something along the lines of: nums = [1, 2, 3] reduce(lambda x, y: x + y, nums) except I'd like to add additional information to the sum that is specific to each element in the list of numbers nums. For example for each pair (a,b) in the list, run the sum as (a+b): nums = [(1, 0), (2, 5), (3, 10)] reduce(lambda x, y: (x[0]+x[1]) + (y[0]+y[1]), nums) This does not work: >>> reduce(lambda x, y: (x[0]+x[1]) + (y[0]+y[1]), nums) Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<stdin>", line 1, in <lambda> TypeError: 'int' object is unsubscriptable Why does it not work? I know I can encode nums as a flat list - that is not the point - I just want to be able to create a reduce operation that can iterate over a list of pairs, or over two lists of the same length simultaneously and pool information from both lists. thanks.

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• On the search for my next great .Net Read

  - by user127954

  Just got done with "The art of unit testing". It was a great read and i think everyone should go buy a copy. With that said i think the next book I'm like to read would be a architecture / Design type book that would focus heavily on building your objects / software in such a way that it would be: Low Coupling High Cohesion Easily Maintainable / Extended Easy to test Easy to Navigate / Debug The above characteristcs are the most important ones but also maybe it would also include (but not necessary) designing for: Performance - Don't want to design a system at at the end find out its dog slow :) Scalability - Again don't want to design something at the end find out it won't scale. I'd also prefer (but not necessary again): Something newer - Architectural principles seem to gradually evolve / improve over time and id like something with current thinking. .Net as illustrating language - like i said above its not mandatory but since its what i use every day id prefer it to be in .net. Doesn't really matter if its in vb.net or c# Some of the topics that would be talked about its how to minimize dependencies and using interfaces throughout your solution rather than concrete classes. Maybe it would constract /compare some of the newest design principles like DDD, Repository Pattern, Ect... I already have "Clean Code" (don't know if its this type of book or not) and "Working effectively with legacy code" on my radar but id like to read a book based upon the topic i talked about above first. Is there such a book?

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• Is it possible, in a django template, to check if an object is contained in a list

  - by AlexH

  I'm very new to django, about a week into it. I'm making a site where users enter stuff, then other users can vote on whether they like the stuff or not. I know it's not so novel, but it's a good project to learn a bunch of tools. I have a many-to-many table for storing who likes or dislikes what. Before I render the page, I pull out all the likes and dislikes for the current user, along with the stuff I'm going to show on the page. When I render the page, I go through the list of stuff I'm going to show and print them out one at a time. I want to show the user which stuff they liked, and which they didn't. So in my django template, I have an object called entry. I also have two lists of objects called likes and dislikes. Is there any way to determine if entry is a member of either list, inside my django template. I think what I'm looking for is a filter where I can say something like {% if entry|in:likes %} or {% if likes|contains:entry %} I know I could add a method to my model and check for each entry individually, but that seems like it would be database intensive. Is there a better way to think about this problem?

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• Difference between MVC FilterAttribute and Filter

  - by zaaaaphod

  I'm trying to write my own custom AuthorizationAttribute that uses DI. I'm using the MUNQ IoC provider for it's speed and have decided to use constructor injection on all my classes as opposed to post instatiation property binding (because I prefer it). I'm trying to write a custom IFilterProvider that will use my IoC container to return requests for filters (so that I can map concrete classes using the container). I've come up with the following. public class FilterProvider : IFilterProvider { private readonly IocContainer _container; public FilterProvider(IocContainer container) { _container = container; } public IEnumerable<Filter> GetFilters(ControllerContext controllerContext, ActionDescriptor actionDescriptor) { var x = Enumerable.Union<Object>(_container.ResolveAll<IActionFilter>(), _container.ResolveAll<IAuthorizationFilter>()); foreach (Filter actionFilter in x) yield return new Filter(actionFilter, FilterScope.First, null); } } The above code will fail during the foreach because my objects that implement IAuthorizationFilter are based on FilterAttribute and not Filter My question is, what is the difference between Filter and FilterAttribute? I would have thought that there would have been a common link between them, unless I'm missing something. Another deeper question is, how come there is no IFilterAttributeProvider that would support IEnumerable GetFilters(...) Is there some other way that I should be using to resolve IAuthorizationFilter via my IoC container? Thank you very much for your help. Z

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• python list/dict property best practice

  - by jterrace

  I have a class object that stores some properties that are lists of other objects. Each of the items in the list has an identifier that can be accessed with the id property. I'd like to be able to read and write from these lists but also be able to access a dictionary keyed by their identifier. Let me illustrate with an example: class Child(object): def __init__(self, id, name): self.id = id self.name = name class Teacher(object): def __init__(self, id, name): self.id = id self.name = name class Classroom(object): def __init__(self, children, teachers): self.children = children self.teachers = teachers classroom = Classroom([Child('389','pete')], [Teacher('829','bob')]) This is a silly example, but it illustrates what I'm trying to do. I'd like to be able to interact with the classroom object like this: #access like a list print classroom.children[0] #append like it's a list classroom.children.append(Child('2344','joe')) #delete from like it's a list classroom.children.pop(0) But I'd also like to be able to access it like it's a dictionary, and the dictionary should be automatically updated when I modify the list: #access like a dict print classroom.childrenById['389'] I realize I could just make it a dict, but I want to avoid code like this: classroom.childrendict[child.id] = child I also might have several of these properties, so I don't want to add functions like addChild, which feels very un-pythonic anyway. Is there a way to somehow subclass dict and/or list and provide all of these functions easily with my class's properties? I'd also like to avoid as much code as possible.

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• Dictionaries with more than one key per value in Python

  - by nickname

  I am attempting to create a nice interface to access a data set where each value has several possible keys. For example, suppose that I have both a number and a name for each value in the data set. I want to be able to access each value using either the number OR the name. I have considered several possible implementations: Using two separate dictionaries, one for the data values organized by number, and one for the data values organized by name. Simply assigning two keys to the same value in a dictionary. Creating dictionaries mapping each name to the corresponding number, and vice versa Attempting to create a hash function that maps each name to a number, etc. (related to the above) Creating an object to encapsulate all three pieces of data, then using one key to map dictionary keys to the objects and simply searching the dictionary to map the other key to the object. None of these seem ideal. The first seems ugly and unmaintainable. The second also seems fragile. The third/fourth seem plausible, but seem to require either much manual specification or an overly complex implementation. Finally, the fifth loses constant-time performance for one of the lookups. In C/C++, I believe that I would use pointers to reference the same piece of data from different keys. I know that the problem is rather similar to a database lookup problem by a non-key column, however, I would like (if possible), to maintain the approximate O(1) performance of Python dictionaries. What is the most Pythonic way to achieve this data structure?

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• Open closed prinicple, problem

  - by Marcus

  Hi, I'm trying to apply OCP to a code snippet I have that in it's current state is really smelly, but I feel I'm not getting all the way to the end. Current code: public abstract class SomeObject {} public class SpecificObject1 : SomeObject {} public class SpecificObject2 : SomeObject {} // Smelly code public class Model { public void Store(SomeObject someObject) { if (someObject is SpecificObject1) {} else if (someObject is SpecificObject2) {} } } That is really ugly, my new approach looks like this: // No so smelly code public class Model { public void Store(SomeObject someObject) { throw new Expception("Not allowed!"); } public void Store(SpecificObject1 someObject) {} public void Store(SpecificObject2 someObject) {} } When a new SomeObject type comes along I must implement how that specific object is stored, this will break OCP cause I need to alter the Model-class. To move the store logic to SomeObject also feels wrong cause then I will violate SRP (?), becuase in this case the SomeObject is almost like a DTO, it's resposibility it not how to know to store itself. If a new implementation to SomeObject comes along who's store implementation is missing I will get a runtime error due to exception in Store method in Model class, it also feels like a code smell. This is because calling code will in the form of IEnumerable<SomeObject> sequence; I will not know the specific types of the sequence objects. I can't seem to grasp the OCP-concept. Anyone has any concrete examples or links that is a bit more than just some Car/Fruit example?

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• f# pattern matching with types

  - by philbrowndotcom

  I'm trying to recursively print out all an objects properties and sub-type properties etc. My object model is as follows... type suggestedFooWidget = { value: float ; hasIncreasedSinceLastPeriod: bool ; } type firmIdentifier = { firmId: int ; firmName: string ; } type authorIdentifier = { authorId: int ; authorName: string ; firm: firmIdentifier ; } type denormalizedSuggestedFooWidgets = { id: int ; ticker: string ; direction: string ; author: authorIdentifier ; totalAbsoluteWidget: suggestedFooWidget ; totalSectorWidget: suggestedFooWidget ; totalExchangeWidget: suggestedFooWidget ; todaysAbsoluteWidget: suggestedFooWidget ; msdAbsoluteWidget: suggestedFooWidget ; msdSectorWidget: suggestedFooWidget ; msdExchangeWidget: suggestedFooWidget ; } And my recursion is based on the following pattern matching... let rec printObj (o : obj) (sb : StringBuilder) (depth : int) let props = o.GetType().GetProperties() let enumer = props.GetEnumerator() while enumer.MoveNext() do let currObj = (enumer.Current : obj) ignore <| match currObj with | :? string as s -> sb.Append(s.ToString()) | :? bool as c -> sb.Append(c.ToString()) | :? int as i -> sb.Append(i.ToString()) | :? float as i -> sb.Append(i.ToString()) | _ -> printObj currObj sb (depth + 1) sb In the debugger I see that currObj is of type string, int, float, etc but it always jumps to the defualt case at the bottom. Any idea why this is happening?

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• What goes into main function?

  - by Woltan

  I am looking for a best practice tip of what goes into the main function of a program using c++. Currently I think two approaches are possible. (Although the "margins" of those approaches can be arbitrarily close to each other) 1: Write a "Master"-class that receives the parameters passed to the main function and handle the complete program in that "Master"-class (Of course you also make use of other classes). Therefore the main function would be reduced to a minimum of lines. #include "MasterClass.h" int main(int args, char* argv[]) { MasterClass MC(args, argv); } 2: Write the "complete" program in the main function making use of user defined objects of course! However there are also global functions involved and the main function can get somewhat large. I am looking for some general guidelines of how to write the main function of a program in c++. I came across this issue by trying to write some unit test for the first approach, which is a little difficult since most of the methods are private. Thx in advance for any help, suggestion, link, ...

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• How to play simultaneous multiply audio sources in Silverlight

  - by Shurup

  I want to play simultaneous multiply audio sources in Silverlight. So I've created a prototype in Silverlight 4 that should play a two mp3 files containing the same ticks sound with an intervall 1 second. So these files must be sounded as one sound if they will be played together with any whole second offsets (0 and 1, 0 and 2, 1 and 1 seconds, etc.) I my prototype I use two MediaElement (me and me2) objects. DateTime startTime; private void Play_Clicked(object sender, RoutedEventArgs e) { me.SetSource(new FileStream(file1), FileMode.Open))); me2.SetSource(new FileStream(file2), FileMode.Open))); var timer = new DispatcherTimer { Interval = TimeSpan.FromMilliseconds(1) }; timer.Tick += RefreshData; timer.Start(); } First file should be played at 00:00 sec. and the second in 00:02 second. void RefreshData(object sender, EventArgs e) { if(me.CurrentState != MediaElementState.Playing) { startTime = DateTime.Now; me.Play(); return; } var elapsed = DateTime.Now - startTime; if(me2.CurrentState != MediaElementState.Playing && elapsed >= TimeSpan.FromSeconds(2)) { me2.Play(); ((DispatcherTimer)sender).Stop(); } } The tracks played every time different and not simultaneous as they should (as one sound).

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• Create a variable which is named depending on an ID number?

  - by gray

  Is there any way to create a variable, and add an ID to the end of the actual variable name? I have a variable called 'gauge', used to create a new Gauge object: var gauge = new Gauge(target).setOptions(opts); I want to add an ID to the variable, so something like: var gauge+id = new Gauge(target).setOptions(opts); It's because I'm creating a number of these objects, and have a specific ID already for each one, which I want to attach to the gauge object if possible? All my code for this function is below, if it gives you a better idea of what i need to do: function go(id, votes) { var val = $('#votes_'+id).text(); var target = document.getElementById('foo_'+id); // your canvas element var gauge = new Gauge(target).setOptions(opts); // create sexy gauge! gauge.maxValue = 100; // set max gauge value gauge.animationSpeed = 20; // set animation speed (32 is default value) var a=votes+0.5; gauge.set(val); // set actual value } My main problem arises on the last line. It says gauge.set(val), and it only sets the last object, ignoring all the other ones...

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• NSMutableArray memory management

  - by chicken

  NSMutableArray *a1 = [[NSMutableArray alloc] init]; NSMutableArray *a2 = [NSMutableArray array]; TempObj *obj = [[TempObj alloc] init]; //assume this line is repeated for each obj [a1 addObject:obj]; [a1 addObject:obj2]; [a1 addObject:obj3]; [a1 addObject:obj4]; [obj release]; [obj2 release]; [obj3 release]; [obj4 release]; [a1 release]; Ok so a2 is an autorelease obj so i dont have to call release on it? Also how do you know when you get an autorelease object? And for a1, i dont have to loop through the array and release each object first? What if i called [a1 removeAllObjects]; does that call [[a1 objectAtIndex:#] release]; Am i supposed to release those objects after ive added them to the array?

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• VB.NET Two different approaches to generic cross-threaded operations; which is better?

  - by BASnappl

  VB.NET 2010, .NET 4 Hello, I recently read about using SynchronizationContext objects to control the execution thread for some code. I have been using a generic subroutine to handle (possibly) cross-thread calls for things like updating UI controls that utilizes Invoke. I'm an amateur and have a hard time understanding the pros and cons of any particular approach. I am looking for some insight on which approach might be preferable and why. Update: This question is motivated, in part, by statements such as the following from the MSDN page on Control.InvokeRequired. An even better solution is to use the SynchronizationContext returned by SynchronizationContext rather than a control for cross-thread marshaling. Method 1: Public Sub InvokeControl(Of T As Control)(ByVal Control As T, ByVal Action As Action(Of T)) If Control.InvokeRequired Then Control.Invoke(New Action(Of T, Action(Of T))(AddressOf InvokeControl), New Object() {Control, Action}) Else Action(Control) End If End Sub Method 2: Public Sub UIAction(Of T As Control)(ByVal Control As T, ByVal Action As Action(Of Control)) SyncContext.Send(New Threading.SendOrPostCallback(Sub() Action(Control)), Nothing) End Sub Where SyncContext is a Threading.SynchronizationContext object defined in the constructor of my UI form: Public Sub New() InitializeComponent() SyncContext = WindowsFormsSynchronizationContext.Current End Sub Then, if I wanted to update a control (e.g., Label1) on the UI form, I would do: InvokeControl(Label1, Sub(x) x.Text = "hello") or UIAction(Label1, Sub(x) x.Text = "hello") So, what do y'all think? Is one way preferred or does it depend on the context? If you have the time, verbosity would be appreciated! Thanks in advance, Brian

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• GUID or int entity key with SQL Compact/EF4?

  - by David Veeneman

  This is a follow-up to an earlier question I posted on EF4 entity keys with SQL Compact. SQL Compact doesn't allow server-generated identity keys, so I am left with creating my own keys as objects are added to the ObjectContext. My first choice would be an integer key, and the previous answer linked to a blog post that shows an extension method that uses the Max operator with a selector expression to find the next available key: public static TResult NextId<TSource, TResult>(this ObjectSet<TSource> table, Expression<Func<TSource, TResult>> selector) where TSource : class { TResult lastId = table.Any() ? table.Max(selector) : default(TResult); if (lastId is int) { lastId = (TResult)(object)(((int)(object)lastId) + 1); } return lastId; } Here's my take on the extension method: It will work fine if the ObjectContext that I am working with has an unfiltered entity set. In that case, the ObjectContext will contain all rows from the data table, and I will get an accurate result. But if the entity set is the result of a query filter, the method will return the last entity key in the filtered entity set, which will not necessarily be the last key in the data table. So I think the extension method won't really work. At this point, the obvious solution seems to be to simply use a GUID as the entity key. That way, I only need to call Guid.NewGuid() method to set the ID property before I add a new entity to my ObjectContext. Here is my question: Is there a simple way of getting the last primary key in the data store from EF4 (without having to create a second ObjectContext for that purpose)? Any other reason not to take the easy way out and simply use a GUID? Thanks for your help.

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• JavaScript: List global variables in IE

  - by Quandary

  I'm trying to get the instance name of my class. The way I do this is I loop through all global objects and compare it with the this pointer. It works in Chrome and FF, but in IE, it doesn't. The problem seems to be the global variables don't seem to be in window. How can I loop through the global variables in IE ? PS: I know it only works as long as there is only one instance, and I don't want to pass the instance's name as a parameter. function myClass() { this.myName = function () { // search through the global object for a name that resolves to this object for (var name in this.global) { if (this.global[name] == this) return name } } } function myClass_chrome() { this.myName = function () { // search through the global object for a name that resolves to this object for (var name in window) { if (window[name] == this) return name ; } } ; } // store the global object, which can be referred to as this at the top level, in a // property on our prototype, so we can refer to it in our object's methods myClass.prototype.global = this //myClass_IE.prototype.global = this // create a global variable referring to an object // var myVar = new myClass() var myVar = new myClass_chrome() //var myVar = new myClass_IE() alert(myVar.myName() );// returns "myVar"

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• GWT + Seam, cannot fetch scoped beans from gwt servlet in seam resource servlet.

  - by David Göransson

  Hello all I am trying to get session and conversation scoped beans to a gwt servlet in the seam resource servlet. I have a conversation scoped bean: @Name ("viewFormCopyAction") @Scope (ScopeType.CONVERSATION) public class ViewFormCopyAction {} and a session scoped bean: @Name ("authenticator") @Scope (ScopeType.SESSION) public class AuthenticatorAction {} There is a RemoteService interface: @RemoteServiceRelativePath ("strokesService") public interface StrokesService extends RemoteService { public Position getPosition (int conversationId); } with corresponding async interface: public interface StrokesServiceAsync extends RemoteService { public void getPosition (int conversationId, AsyncCallback callback); } and implementation: @Name ("com.web.actions.forms.gwt.client.StrokesService") @Scope (ScopeType.EVENT) public class StrokesServiceImpl implements StrokesService { @In Manager manager; @Override @WebRemote public Position getPosition (int conversationId) { manager.switchConversation( "" + conversationId ); ViewFormCopyAction vfca = (ViewFormCopyAction) Component.getInstance( "viewFormCopyAction" ); AuthenticatorAction aa = (AuthenticatorAction) Component.getInstance( "authenticator" ); return null; } } The gwt page is within an IFrame in a regular seam page and the conversationId is propagted with the src attribute of the IFrame. Both bean objects end up with only null values. Can anyone see anything wrong with the code? I know that I could use strings instead of the int, but never mind that at this point.

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• Basic problems (type inference or something else?) in Objective-C/Cocoa.

  - by Matt

  Hi, Apologies for how basic these questions are to some. Just started learning Cocoa, working through Hillegass' book, and am trying to write my first program (a GUI Cocoa app that counts the number of characters in a string). I tried this: NSString *string = [textField stringValue]; NSUInteger *stringLength = [string length]; NSString *countString = (@"There are %u characters",stringLength); [label setStringValue:countString]; But I'm getting errors like: Incompatible pointer conversion initializing 'NSUInteger' (aka 'unsigned long'), expected 'NSUInteger *'[-pedantic] for the first line, and this for the second line: Incompatible pointer types initializing 'NSUInteger *', expected 'NSString *' [-pedantic] I did try this first, but it didn't work either: [label setStringValue:[NSString stringWithFormat:@"There are %u characters",[[textField stringValue] length]]] On a similar note, I've only written in easy scripting languages before now, and I'm not sure when I should be allocing/initing objects and when I shouldn't. For example, when is it okay to do this: NSString *myString = @"foo"; or int *length = 5; instead of this: NSString *myString = [[NSString alloc] initWithString:"foo"]; And which ones should I be putting into the header files? I did check Apple's documentation, and CocoaDev, and the book I'm working for but without luck. Maybe I'm looking in the wrong places.. Thanks to anyone who takes the time to reply this: it's appreciated, and thanks for being patient with a beginner. We all start somewhere. EDIT Okay, I tried the following again: [label setStringValue:[NSString stringWithFormat:@"There are %u characters",[[textField stringValue] length]]] And it actually worked this time. Not sure why it didn't the first time, though I think I might have typed %d instead of %u by mistake. However I still don't understand why the code I posted at the top of my original post doesn't work, and I have no idea what the errors mean, and I'd very much like to know because it seems like I'm missing something important there.

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• NHibernate: What are child sessions and why and when should I use them?

  - by stefando

  In the comments for the ayende's blog about the auditing in NHibernate there is a mention about the need to use a child session:session.GetSession(EntityMode.Poco). As far as I understand it, it has something to do with the order of the SQL operation which session.Flush will emit. (For example: If I wanted to perform some delete operation in the pre-insert event but the session was already done with deleting operations, I would need some way to inject them in.) However I did not find documentation about this feature and behavior. Questions: Is my understanding of child sessions correct? How and in which scenarios should I use them? Are they documented somewhere? Could they be used for session "scoping"? (For example: I open the master session which will hold some data and then I create 2 child-sessions from the master one. I'd expect that the two child-scopes will be separated but the will share objects from the master session cache. Is this the case?) Are they first class citizens in NHibernate or are they just hack to support some edge-case scenarios? Thanks in advance for any info.

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• transfering a container of data to different classes

  - by user340699

  I am passing a vector of bids from Trader class to Simulator class.which class then passes it on to the auctioneer class.something seems messed up, can anyone spot it please. Below is part of the code: Error: 199 expected primary-expression before '&' token //Class of Origin of the vector. class Trader { private: int nextBidId; public: Trader(); ~Trader(){}; Bid getNextBid(); Bid getNextBid(int trdId, int qty, int price, char type); void loadRange( vector <Bid> & bids ) {} ; void loadRange(BidList &, int trdId, int qty, int price, char type, int size); }; //To be received by the Simulator class Simulator { vector <Bid> list; Trader trader; Auctioneer auctioneer; public: void run(); }; // Passing the vector into a function in simulator Simulator::accept_bids(bid_vector::const_iterator begin, bid_vector::const_iterator end){ vector<Bid>::iterator itr; } //Its journey should end with the Auctioneer. who displays the data class Auctioneer { public: vector <Bid>v2;// created a new vector to hold the objects void accept_bids(vector<Bid> & bids); void displayBids(){return bids} };

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• Instrumenting a string

  - by George Polevoy

  Somewhere in C++ era i have crafted a library, which enabled string representation of the computation history. Having a math expression like: TScalar Compute(TScalar a, TScalar b, TScalar c) { return ( a + b ) * c; } I could render it's string representation: r = Compute(VerbalScalar("a", 1), VerbalScalar("b", 2), VerbalScalar("c", 3)); Assert.AreEqual(9, r.Value); Assert.AreEqual("(a+b)*c==(1+2)*3", r.History ); C++ operator overloading allowed for substitution of a simple type with a complex self-tracking entity with an internal tree representation of everything happening with the objects. Now i would like to have the same possibility for NET strings, only instead of variable names i would like to see a stack traces of all the places in code which affected a string. And i want it to work with existing code, and existing compiled assemblies. Also i want all this to hook into visual studio debugger, so i could set a breakpoint, and see everything that happened with a string. Which technology would allow this kind of things? I know it sound like an utopia, but I think visual studio code coverage tools actually do the same kind of job while instrumenting the assemblies.

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• perl - universal operator overload

  - by Todd Freed

  I have an idea for perl, and I'm trying to figure out the best way to implement it. The idea is to have new versions of every operator which consider the undefined value as the identity of that operation. For example: $a = undef + 5; # undef treated as 0, so $a = 5 $a = undef . "foo"; # undef treated as '', so $a = foo $a = undef && 1; # undef treated as false, $a = true and so forth. ideally, this would be in the language as a pragma, or something. use operators::awesome; However, I would be satisfied if I could implement this special logic myself, and then invoke it where needed: use My::Operators; The problem is that if I say "use overload" inside My::Operators only affects objects blessed into My::Operators. So the question is: is there a way (with "use overoad" or otherwise) to do a "universal operator overload" - which would be called for all operations, not just operations on blessed scalars. If not - who thinks this would be a great idea !? It would save me a TON of this kind of code if($object && $object{value} && $object{value} == 15) replace with if($object{value} == 15) ## the special "is-equal-to" operator

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• NHibernate will not insert a record

  - by Brian Beckham

  I have an application that is now 4+ years old that is exhibiting some odd behavior on our latest deployment. The application uses nHibernate for all inserts / updates / selects, etc. We are currently using .NET 2.0, and nHibernate 1.2 (I know, we need to upgrade) This deployment is on Windows 2008 Server x64, IIS 7.5 - what I have seen so far is that the application runs, but is unable to insert or update records in the DB - reads seem fine so far, but writes are a problem. SOME writes actually work, inserts into some small tables, but most never even make it to the DB. Using SQL Profiler, the insert / updates never make it to the server, and turning log4net up to DEBUG, and show_sql true - the select statements appear, but the insert / update statements never make it into the log at all, and never show up at the server. What's even more odd is that the application seems to be oblivious to this - the commandandclose runs without exception (open session in view with an httpmodule), the domain objects come back with uuid's generated, etc. but never get persisted. Certainly an upgrade is due, but I would hate to try it during a deployment, and without time to accurately test the app. Any ideas?

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• How to map a 0..1 to 1 relationship in Entity Framework 3

  - by sako73

  I have two tables, Users, and Address. A the user table has a field that maps to the primary key of the address table. This field can be null. In plain english, Address exist independent of other objects. A user may be associated with one address. In the database, I have this set up as a foreign key relationship. I am attempting to map this relationship in the Entity Framework. I am getting errors on the following code: <Association Name="fk_UserAddress"> <End Role="User" Type="GenesisEntityModel.Store.User" Multiplicity="1"/> <End Role="Address" Type="GenesisEntityModel.Store.Address" Multiplicity="0..1" /> <ReferentialConstraint> <Principal Role="Address"> <PropertyRef Name="addressId"/> </Principal> <Dependent Role="User"> <PropertyRef Name="addressId"/> </Dependent> </ReferentialConstraint> </Association> It is giving a "The Lower Bound of the multiplicity must be 0" error. I would appreciate it if anyone could explain the error, and the best way to solve it. Thanks for any help.

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