LINQ Take Two Realizing the LINQ to Everything

LINQ, Take Two Realizing the LINQ to Everything Dream Bart J. F. De Smet blogs. bartdesmet. net/bartde@microsoft. com

A Historical Perspective 5 years ago Little recent innovation Censored Where’s the cloud?

Monads Language Integrated Query Why? How? What?

The Monadic Bind Operator Revealed IEnumerable<T> IQueryable<T> Could there be more? new[] { 42 } Select. Many IEnumerable<R> Select. Many<T, R>( this IEnumerable<T> source, Func<T, IEnumerable<R>> selector) Also see www. codeplex. com/LINQSQO for “Project Min. LINQ”

Building the Maybe Monad (For Fun and No Profit) Null-propagating dot One single library function suffices string s = name? . To. Upper(); Syntactic sugar from _ in name from s in _. To. Upper() select s Compiler name. Select. Many( _ => _. To. Upper(), s => s)

DEMO Essential LINQ

Query Providers Revisited – Do We Need IQueryable<T>? Implements IQueryable<T> var src = new Source<Product>(); var res = from p in src where p. Price > 100 m group p by p. Category; Compiles fine foreach (var p in res) Console. Write. Line(p); Does it really have to be a runtime check?

Leveraging The Query Pattern var res = from p in src where p. Price > 100 m Syntactic sugar group p by p. Category; var res = src. Where(p => p. Price > 100 m). Group. By(p => p. Category); No Group. By “edge” Can be instance methods Source<T> Where Filtered<T> Select Projected<T>

Taking It One Step Further var res = from tweet in twitter Query “learns” class Tweet. About. From. Loc class Tweet. About. Loc { { where tweet. From == “Bart” public From. String From; public About. String About; About From == “LINQ” public Loc. String Location; where tweet. About public Loc. String Location; From } } select tweet; About Location “Has a” type class About. String class From. String Recipe { { Filter. About operator ==( Filter. From operator ==( Method overloads About. String f, string s) From. String f, machine string s) Type state } From operator overloading } Operator overloads class Twitter. By. From { public Twitter. By. From Twitter. By. About. From Where(Func<Tweet. About. From. Loc, Where(Func<Tweet. About. Loc, Filter. From> Filter. About> filter); // Other filter methods } // Fields with current filters } Custom syntax trees

DEMO Query Providers Revisited

Event Processing Systems Way simpler with Rx Rx is a library for composing asynchronous and event-based programs using observable sequences. Queries! LINQ! • • • . NET 3. 5 SP 1 and 4. 0 Silverlight 3, 4, and 5 XNA 4. 0 for Xbox 360 Windows Phone 7 Java. Script (Rx. JS) Download at MSDN Data Developer Center or use Nu. Get

Push-Based Data Retrieval Move. Next IEnumerable<T> IEnumerator<T> Environment Have next! IObservable<T> IObserver<T> Reactive Got next? On. Next Interactive Application

Event Programming Interfaces Both interfaces ship in the. NET 4 BCL interface IObservable<out T> { IDisposable Subscribe(IObserver<T> observer); } interface IObserver<in T> { void On. Next(T value); void On. Error(Exception ex); void On. Completed(); }

How? As. Queryable (MSIL) To. Observable Pull e? rre ler) r he ncu edu (interactive) Threads Worker pools Duality As. Qbservable (Expression trees) Translatable Homo-iconic Fixed LINQ to *. * As. Observable LINQ to Objects y nc W Co Sch (I As. Enumerable IEnumerable<T> LINQ to WMI Events To. Enumerable LINQ to SQL IQbservable<T> To. Queryable IQueryable<T> To. Qbservable IObservable<T> LINQ to Events Push What? (reactive) Message loops Distributed

IQbservable<T> – The Dual of IQueryable<T> interface IQbservable<out T> : IObservable<T> { Expression { get; } Type Element. Type { get; } IQbservable. Provider { get; } } We welcome semantic discussions Extended role for some operators No Execute interface IQbservable. Provider method { IQbservable<R> Create. Query<R>(Expression expression); }

DEMO LINQ to WMI Events (WQL)

Rx and the Visual Studio Async CTP • The essence of the feature Result is async too Asynchronously computed value async Task<int> Get. Length(Task<string> name) { string n = await name; Can await a return n. Length; “future” value } • Feature based on the “await-pattern” • Awaiting Task<T> • Returns the single result (of type T) • Awaiting IObservable<T>? • We return the last result (of type T) • Want all values? Use To. List() first!

Asynchronous Pull-Based Data Access? • Await feature is about sequential code • Great for single-valued computations • What about asynchronous pull-based data collections? public interface IAsync. Enumerable<T> { IAsync. Enumerator<T> Get. Enumerator(); } Can await Rx defines Query Operators public interface IAsync. Enumerator<T> : IDisposable { T Current { get; } Task<bool> Move. Next(); }

DEMO Rx support for C# and VB “await”

Where Execution Happens – Introducing Schedulers Rx’s unified way to introduce concurrency interface IScheduler { Date. Time. Offset Now { get; } IDisposable Schedule<T>(T state, Func<IScheduler, T, IDisposable> action); IDisposable Schedule<T>(T state, Time. Span due. Time, Func<IScheduler, T, IDisposable> action); IDisposable Schedule<T>(T state, Date. Time. Offset due. Time, Func<IScheduler, T, IDisposable> action); } To. Observable IObservable<T> IEnumerable<T> To. Enumerable Synchronous Asynchronous

IScheduler Specifies Where Things Happen Imported Text. Box Text. Changed event var res = from word in input. Distinct. Until. Changed(). Throttle(Time. Span. From. Seconds(0. 5)) from words in lookup(word) Asynchronous select words; web service call Indicates where things run Use of scheduler to synchronize res. Subscribe(words => res. Observe. On(new Control. Scheduler(frm)). Subscribe(words => { lst. Items. Clear(); lst. Items. Add. Range((from word in words select word. Word). To. Array()); });

IScheduler Parameterization Baked in notion of “where”? Entry-point for the schema var ctx = new Northwind. Data. Context(); var res = from product in ctx. Products where product. Price > 100 m select product. Name; Custom schedulers could be very rich (e. g. server farm) Decoupled “what” from “where” foreach (var p in res. Remote. On(new Sql. Scheduler(“server”))) // Process product

Expression Tree Remoting Rx. NET from ticker in stocks where ticker. Symbol == “MSFT” select ticker. Quote Retargeting to AJAX Rx. JS JSON Observable data source serializer stocks. Where(function (t) { return t. Symbol == “MSFT”; }). Select(function (t) { return t. Quote; })

DEMO Remoting of Query Expressions

LINQ to the Unexpected Refinement % Model[ Decisions[Reals, SA, VZ], Goals[ Minimize[20 * SA + 15 * VZ] ], Cost / barrel Constraints[ C 1 -> 0. 3 * SA + 0. 4 * VZ >= 2000, C 2 -> 0. 4 * SA + 0. 2 * VZ >= 1500, C 3 -> 0. 2 * SA + 0. 3 * VZ >= 500, C 4 -> SA <= 9000, Max C 5 -> VZ <= 6000, # barrels C 6 -> SA >= 0, Min C 7 -> VZ >= 0 # barrels ] ] Non-persistent from m in ctx. Create. Model(new { vz = default(double), sa = default(double) }) where 0. 3 * m. sa + 0. 4 * m. vz >= 2000 && 0. 4 * m. sa + 0. 2 * m. vz >= 1500 && 0. 2 * m. sa + 0. 3 * m. vz >= 500 where 0 <= m. sa && m. sa <= 9000 && 0 <= m. vz && m. vz <= 6000 orderby 20 * m. sa + 15 * m. vz select m To compute call Solve

Select. Many LINQ to the Unexpected Subscribe here! from cost. SA in Get. Price. Monitor("SA") from cost. VZ in Get. Price. Monitor("VZ") Observable data sources from m in ctx. Create. Model( new { vz = default(double), sa = default(double) }) where 0. 3 * m. sa + 0. 4 * m. vz >= 2000 && 0. 4 * m. sa + 0. 2 * m. vz >= 1500 && 0. 2 * m. sa + 0. 3 * m. vz >= 500 where 0 <= m. sa && m. sa <= 9000 && 0 <= m. vz && m. vz <= 6000 orderby cost. SA * m. sa + cost. VZ * m. vz select m Parameters to decision

DEMO Theorem Solving using Z 3

A Futuristic Perspective Next 5 years Remoting Async Rx and Ix are here Solvers Toolkits Scheduler Censored

Stay up to date with MSDN Belux • Register for our newsletters and stay up to date: http: //www. msdn-newsletters. be • Technical updates • Event announcements and registration • Top downloads • Follow our blog Download http: //blogs. msdn. com/belux MSDN/Tech. Net Desktop Gadget http: //bit. ly/msdntngadget • Join us on Facebook http: //www. facebook. com/msdnbelux • Linked. In: http: //linkd. in/msdnbelux/ • Twitter: @msdnbelux

Tech. Days 2011 On-Demand • Watch this session on-demand via Channel 9 http: //channel 9. msdn. com/belux • Download to your favorite MP 3 or video player • Get access to slides and recommended resources by the speakers

THANK YOU