Esoteric LINQ and Structural Madness
Download as PPTX, PDF0 likes772 views
This document provides an agenda for a presentation on esoteric LINQ and structural madness. The agenda includes background information on data structures like graphs, trees, and lists. It also covers design patterns like iterator, observer, visitor, and specification. The document then provides primers on LINQ and how it can be applied to functions, graphs, and specifications. The presentation aims to explore advanced and unconventional applications of LINQ through functional combinators and predicate logic.
Esoteric LINQ and Structural Madness
- 1. Esoteric LINQ AND STRUCTURAL MADNESS
- 2. I Think Therefore I Am Chris Eargle Mad Scientist Telerik Evangelist C# MVP INETA Board of Directors Contacts kodefuguru.com kodefuguru@live.com callto://kodefuguru
- 3. “ It is not enough to have a good mind; the main thing is to use it well. RENE DESCARTES ” Prepare(); var mind = blown;
- 4. This presentation is brought to you by Telerik. Don’t worry. This is hardcore ideas and code, not a sales pitch.
- 5. Agenda Background Information Data Structures Design Patterns LINQ LINQ to Functions LINQ to Graphs LINQ to Specifications
- 7. Common Data Structures Primitive Types Composite Types Abstract Types
- 8. Primitive Types These are struct types in C# Represents a single value Examples: bool, char, float, int
- 9. Composite Types In C#, everything else is a form of a composite type Typical examples Array Record Tuple Struct (not the C# struct) Plain Old Data Structure Union Tagged Union – Union that tracks current type Object – Data + Behavior
- 10. Abstract Types These are abstract composite types, structural implementations vary Examples Dictionary List Set Tree Graph
- 11. Graph Composed of nodes (or vertices) and edges Node 1 2 Edge 3 4 5
- 12. Digraph Apply a direction Removing direction is called the “underlying graph.” 1 2 3 4 5
- 13. Weighted Graph Edge contains value Useful for determining optimal routes between destinations 2.2 1 2 3.7 6.0 1.5 0.5 3 4 5
- 14. Multigraph More than one edge allowed between nodes 1 2 3 4 5
- 15. Hypergraph Edges can connect more than two nodes I view hyper-edges as categories 1 2 3 4 5
- 16. Tree A graph with parent-child relationships No node can be the child of more than one node 1 2 3 4 5 6
- 17. List A graph where each node is connected to 1 or 2 nodes Explicitly has an order 1 2 3 4 5
- 18. Set Comparisons List – Ordered, allows duplicates, single type Tuple – Ordered, allows duplicates, multiple types Set – Unordered, no duplicates, single type
- 20. “ A general reusable solution to a commonly occurring problem. WIKIPEDIA ” Even if you do not know design patterns, you’ve probably used them.
- 21. Types of Design Patterns Creational Patterns Structural Patterns Behavioral Patterns Concurrency Patterns Architectural Patterns
- 22. Structural Patterns Difference with Data Structures Focus is to use structure to enable behavior There is potential overlap with abstract types Examples Adapter Composite Decorator Façade Flyweight
- 23. Behavioral Patterns Difference with Structural Behavior isn’t necessarily driven by the structure Examples Chain of Responsibility Command Iterator Observer Specification Visitor
- 24. Iterator an object that provides a standard way to examine all element of any collection. Has a uniform interface for traversing many data structure without exposing their implementations. Supports concurrent iteration and element removal. No need to know the internal structure of collection.
- 25. Iterator Aggregate Client Iterator <<interface>> <<interface>> + CreateIterator() + First() + Next() + IsDone() + CurrentItem ConcreteAggregate ConcreteIterator + CreateIterator()
- 26. Observer An object, called the subject, maintains a list of its dependents Dependents are known as observers Observers are notified when subject’s state changes
- 27. Observer Subject Observer +observers +Register(observer) +Notify() +Unregister(observer) +Notify() ConcreteObserverA ConcreteObserverB +Notify()
- 28. Visitor Separates an algorithm from the structure on which it operates
- 29. Visitor Elementlike Client Visitable <<interface>> <<interface>> +Accept(visitable) +Visit(element) Element Visitor +Accept(visitable)
- 30. Specification Separates business rules from business objects Represents object-oriented predicates and predicate combinators Predicate – conditionals that can be passed The pattern uses “IsSpecifiedBy” to indicate whether the predicate is successful
- 31. Specification ISpecification CompositeSpecification <<Interface>> +And() +And() +IsSatisfiedBy() +IsSatisfiedBy() +Not() +Not() +Or() +Or() AndSpecification OrSpecification NotSpecification +left : ISpecification +left : ISpecification +right : ISpecification +right : ISpecification +wrapped : ISpecification
- 32. LINQ A PRIMER
- 33. Language Integrated Query Interrogate / manipulate data Type safe Misunderstood
- 34. Example Query from x in object1 from y in object2 select x + y; What can you tell me about object1?
- 35. LINQ to Objects This is LINQ over the iterator pattern The iterator pattern in C# is implemented with IEnumerable Much more declarative than foreach loops Lazy Execution
- 36. LINQ to SQL/EF/Etc Uses visitor pattern Lambdas represent Expressions rather than functions Visitor translates expressions into another language
- 37. Reactive LINQ to observer pattern Items are pushed instead of pulled Great for asynchronous programming Is now open source
- 38. Materialization sequence.ToList(); This is typically wrong.
- 39. Materialization sequence.Materialize(); public static IEnumberable<T> Materialize( this IEnumerable<T> sequence) { return sequence.ToArray(); }
- 40. Memoization Best of both worlds: Lazy Execution and Materialized results Cache results as collection is iterated
- 41. Code
- 42. LINQ to Functions FUNCTIONAL COMBINATORS
- 43. What Does LINQ to Functions Mean Applying LINQ to new forms require reimagining the DSL In the case of functions, LINQ combines functions Each LINQ method is a functional combinator
- 44. “ a combinator is a function which builds program fragments from program fragments… JOHN HUGHES ”
- 45. Code
- 46. LINQ to Graphs VERTICES AND EDGES
- 47. Select 1 2 v` + 1 2 3 Select 3 4
- 48. SelectMany 1 2 v` + w` 2 3 3 4 1 2 , SelectMany 3 4 5
- 49. SelectMany Expand 2 3 3 4 4 5
- 50. SelectMany 2 3 Fold 4 5
- 51. Where 1 2 v` % 2 == 1 Where 1 3 3
- 52. Code
- 53. LINQ to Specifications PREDICATE COMBINATORS
- 54. Explanation Predicates are functions, but they combine differently than other functions Therefore, it makes more sense to wrap them so specific combinators can be applied
- 55. LINQ Weirdness from x in specification where x != 0 select !x;
- 56. Code
- 57. Q&A