Comment Feed for Channel 9 - Erik Meijer, Immo Landwerth, and Andrew Arnott: Immutable Collections for .NET http://media.ch9.ms/ch9/087a/672f4fbe-9c7b-49fb-982e-6c1d69ae087a/E2EImmutableCollectionsNET_100.jpg Channel 9 - Erik Meijer, Immo Landwerth, and Andrew Arnott: Immutable Collections for .NET Erik Meijer interviews .NET team PM Immo Landwerth and Software Developer Andrew Arnott. The topic is Immutable Collections, a new set of immutable types for .NET. You can play around with these today as part of a preview release (NuGet link below). Tune in! Niners asked questions in advance and some of them were addressed. Thanks again for asking and sorry we didn't get to all of them, but many of the topics were covered (what, why, how, etc...). Over the last years .NET added many features to make writing multithreaded applications easier. This includes the Task Parallel Library (TPL) as well as the new async/await keywords features to reduce the friction when writing asynchronous code. However, it's still challenging to keep mutable state under control when multiple threads are involved. A common approach is to make use of immutable state that can be passed freely between different threads. - Immo Landwerth The NuGet package preview includes these types: ImmutableStack<T> ImmutableQueue<T> ImmutableList<T> ImmutableHashSet<T> ImmutableSortedSet<T> ImmutableDictionary<K, V> ImmutableSortedDictionary<K, V> Interfaces for each of these types are also defined to facilitate exchange of immutable collection types that may be implemented differently to optimize for very specific performance or memory requirements. See Andrew's blog for more detailed information (on immutable types for .NET and more. Lots of great info...). en Thu, 23 May 2013 04:10:15 GMT Thu, 23 May 2013 04:10:15 GMT Rev9 Re: Erik Meijer, Immo Landwerth, and Andrew Arnott: Immutable Collections for .NET Great discussion.  I've moved away from ConcurrentQueue and ConcurrentDictionary Collections in favor of ImmutableList and ImmutableDictionary collections on a high performance a WCF service that uses TPL extensively.  I noticed a nice performance increase on the larger collections when iterating through larger collections.

For everyone getting started, the only real gotcha I've found is to remember to take the return result and assign it to the collection like so:

var tmpCollection = ImmutableList<string>.Empty;

tmpCollection = tmpCollection.Add("Test");

Overall though, I am very pleased with the new Collections, kudos to your team!

posted by JarredCapellman

]]> http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634939564931721434 Wed, 16 Jan 2013 18:08:13 GMT http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634939564931721434 JarredCapellman Re: Erik Meijer, Immo Landwerth, and Andrew Arnott: Immutable Collections for .NET I guess we have to thank Roslyn project (at least in part) for these collections Smiley

posted by mdonatas

]]> http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634939664920894947 Wed, 16 Jan 2013 20:54:52 GMT http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634939664920894947 mdonatas Re: Erik Meijer, Immo Landwerth, and Andrew Arnott: Immutable Collections for .NET @Jarred: Yep, that's a common mistake when starting to use these new collections Smiley

@mdonatas: In fact that thank goes straight to Andrew Arnott - he wrote the immutable collections that Roslyn uses. However, you are right from the perspective that Roslyn definitely created a need for bringing a common way to represent immutable collections to the BCL.

posted by terrajobst

]]> http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634939691871118750 Wed, 16 Jan 2013 21:39:47 GMT http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634939691871118750 terrajobst Re: Erik Meijer, Immo Landwerth, and Andrew Arnott: Immutable Collections for .NET Nice interview.

There are also some immtuable F# collections and it would be interesting to compare to those.

I like the builder pattern - not that it's necessary but the optimization it affords. It's also interesting to hear how much defensive coding is inside VS around collections. Immutability where possible just gives peace of mind and static guarantees. It is almost like dependent types where you can express a value constraint statically. 

The thing about sharing (and deep immutability) was also interesting, it kind of reminded me of smart pointers but it could have been expanded further by Erik.

It seemed like there was material enough for more talk but this was fun.

Smiley

posted by exoteric

]]> http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634939772715776112 Wed, 16 Jan 2013 23:54:31 GMT http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634939772715776112 exoteric Re: Erik Meijer, Immo Landwerth, and Andrew Arnott: Immutable Collections for .NET @exoteric: We can always dig in further.

C

posted by Charles

]]> http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634939801308053435 Thu, 17 Jan 2013 00:42:10 GMT http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634939801308053435 Charles Re: Erik Meijer, Immo Landwerth, and Andrew Arnott: Immutable Collections for .NET
I would really like the BCL team to reconsider the naming, this is an log2 version of persistent collections: http://en.wikipedia.org/wiki/Persistent_data_structure I think most agree that the idea originates from Chris Okasaki book (references in the wikipedia page)

Please do not rename a known CS concept out of ignorance.

posted by oskark

]]> http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634940089038967356 Thu, 17 Jan 2013 08:41:43 GMT http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634940089038967356 oskark Re: Erik Meijer, Immo Landwerth, and Andrew Arnott: Immutable Collections for .NET
So I don't think it would be a good idea to name them Persistent Collections, because that would be confusing, don't you think?

posted by Dave Van den Eynde

]]> http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634940175282760080 Thu, 17 Jan 2013 11:05:28 GMT http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634940175282760080 Dave Van den Eynde Re: Erik Meijer, Immo Landwerth, and Andrew Arnott: Immutable Collections for .NET cool stuff Smiley

but I don't get the whole Add/AddRange problem, the following code work just fine right? am I missing something?

    public class List<T>
    {
        public void Add(T item){
        
        }
        public void Add(IEnumerable<T> items) { 
        
        }
    }
...
test.Add("hello");
test.Add(new[] { "world" });

posted by aL3891

]]> http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634940204504663717 Thu, 17 Jan 2013 11:54:10 GMT http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634940204504663717 aL3891 Re: Erik Meijer, Immo Landwerth, and Andrew Arnott: Immutable Collections for .NET I do wonder about deep immutability. It seems like freezeable objects and collections are generally a nice paradigm but in particular domain classes are painful to make freezable and edit without some language support. Say you want to either change a.b.c or get a new version of a with a new b with a new c, then you could have operations for that ("example syntax")

var x = a.b.c <- x // new immutable version

var y = a.b.c := x // new mutable version

y.b.c := z // destructive update of mutable version

a.p <~ b.x + c.x //  a reactive expression propagated to a.p (binq?)

And how about having time or cardinality buffering constraints on properties... select back in time? See properties as cursors in temporal collections? Automatic persistence to versioned db? Capture and replay user interface session from "tape"?

Is there a language waiting to be conceived with even tighter integration for time, immutablity, mutability, async, push, pull, dependency properties, etc. with the benefit of hindsight?

Ahh well at least we now have both great libraries and good language support.

posted by exoteric

]]> http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634940771925113064 Fri, 18 Jan 2013 03:39:52 GMT http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634940771925113064 exoteric Re: Erik Meijer, Immo Landwerth, and Andrew Arnott: Immutable Collections for .NET
How are you (is the compiler?) supposed to determine whether the collection is added as a single item or whether to enumerate all the items in the collection and add them individually?

posted by woopsie

]]> http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634940849906650444 Fri, 18 Jan 2013 05:49:50 GMT http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634940849906650444 woopsie Re: Erik Meijer, Immo Landwerth, and Andrew Arnott: Immutable Collections for .NET @al3891: You're right -- the example I gave in the video is busted. In fact, Erik caught me on this during the interview but he was kind enough not calling it out Wink

The C# compiler is able to resolve the overload because T is more specific than IEnumerable<T>. In other words, the compiler favors identity conversions over any implicit conversions. Theoretically you could envision that other compilers might handle this differently, but I kinda doubt that;s a realistic assumption.

However, it's possible to construct ambiguous cases:

class MyList<T>
{
    public void Add(T item) {}
    public void Add(IEnumerable<T> item) {}
}
class Base {}
class Derived : Base, IEnumerable<Base>
{
    public IEnumerator<Base> GetEnumerator()
    {
        return null;
    }
    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }
}
var list = new MyList<Base>();
list.Add(new Derived());

Now is that a big deal? Probably not because you can resolve this conflict easily using a cast and it's not a very common scenario.

Well, why are we following the existing naming convention then? Because it's an existing naming convention. If you can do (A) or (B) but (A) is already established we favor (A) unless (B) offers a significant improvement. In this case I don't think it does.

posted by terrajobst

]]> http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634940865248087482 Fri, 18 Jan 2013 06:15:24 GMT http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634940865248087482 terrajobst Re: Erik Meijer, Immo Landwerth, and Andrew Arnott: Immutable Collections for .NET posted by Amit

]]> http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634942686877408236 Sun, 20 Jan 2013 08:51:27 GMT http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634942686877408236 Amit Re: Erik Meijer, Immo Landwerth, and Andrew Arnott: Immutable Collections for .NET
Successfully installed 'Microsoft.Bcl.Immutable 1.0.5-beta'.
Successfully uninstalled 'Validation 2.0.1.12362'.
Install failed. Rolling back...
Install-Package : Could not install package 'Validation 2.0.1.12362'. You are trying to install this package into a project that
targets '.NETFramework,Version=v4.5', but the package does not contain any assembly references that are compatible with that
framework. For more information, contact the package author.
...

Any idea what am I doing wrong please?

posted by Usman ur Rehman Ahmed

]]> http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634942803568636991 Sun, 20 Jan 2013 12:05:56 GMT http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634942803568636991 Usman ur Rehman Ahmed Re: Erik Meijer, Immo Landwerth, and Andrew Arnott: Immutable Collections for .NET @Amit: Demoted? Second class? Why would you state this? It's not true...
C

posted by Charles

]]> http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634943123876563402 Sun, 20 Jan 2013 20:59:47 GMT http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634943123876563402 Charles Re: Erik Meijer, Immo Landwerth, and Andrew Arnott: Immutable Collections for .NET

The BCL blog post http://blogs.msdn.com/b/bclteam/archive/2012/12/18/preview-of-immutable-collections-released-on-nuget.aspx suggests that the release of NUGet package is for .NET Framework 4.5 but during installation I stumbled upon following issue,

Successfully installed 'Microsoft.Bcl.Immutable 1.0.5-beta'.
Successfully uninstalled 'Validation 2.0.1.12362'.
Install failed. Rolling back...
Install-Package : Could not install package 'Validation 2.0.1.12362'. You are trying to install this package into a project that
targets '.NETFramework,Version=v4.5', but the package does not contain any assembly references that are compatible with that
framework. For more information, contact the package author.
...

Any idea what am I doing wrong please?

 

Yes -- you are using a NuGet 2.0. Make sure you've updated to NuGet 2.1 or higher. Just open VS and go to Extras | Extensions and Updates | Updates. There is probably a NuGet 2.2 knocking on your door Smiley

posted by terrajobst

]]> http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634943157350336336 Sun, 20 Jan 2013 21:55:35 GMT http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634943157350336336 terrajobst Re: Erik Meijer, Immo Landwerth, and Andrew Arnott: Immutable Collections for .NET

Nice addition! But I wonder for how long they will be relevant? In Win8 apps! where HTML5, Javascript and C++ are first class citizens and .NET has been demoted to second class citizen?

First of all I don't think that's true. I was the PM driving the .NET surface area you can use when targeting Windows 8 store apps. Let me tell you: the entire .NET Framework team and large chunks of Visual Studio spend significant amount of resources to make this an awesome experience. As with every technology that is advanced enough by adding a non-trivial set of features, there are rough edges and I'm the first to admit that. However, the same is true for C++ and JavaScript given that Windows Store apps run in a different environment that are new for them, too. We all try very hard to make writing Windows Store apps as easy and smooth an experience as possible.

Secondly, looking back to the days when Microsoft announced .NET, I think we've learned from that in the sense that we no longer promote a single technology to rule them all. We've made the mistake with .NET which lead to unrealistic expectations what .NET would deliver. I believe the .NET platform is the most productive development platform out there (otherwise I wouldn't work here) but I also believe it's not for everybody. Different tasks require different tools. And someone needs to write the CLR as well Wink

Rest assured that .NET isn't going away any time soon. You don't need to take my word for it -- just think of all the products Microsoft offers that are written in managed code.

For platforms like Windows the key is offering choice. Some might have a strong web background with JavaScript. Others come from the native world and prefer C/C++. Others are .NET developers.

My advice: ignore marketing and choose what you feel comfortable with and what gets the job done best.

posted by terrajobst

]]> http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634943171136645665 Sun, 20 Jan 2013 22:18:33 GMT http://channel9.msdn.com/posts/Erik-Meijer-Immo-Landwerth-and-Andrew-Arnott-Immutable-Collections-for-NET#c634943171136645665 terrajobst