Knowing .NET

Inspired by Jon Udell's link to a New York Times article on network maps of polarized political books, I wrote a similar program in C# and mapped the polarization between readers of "The C# Programming Language" by Hejlsberg et al. and "The Java Programming Language" by Arnold et al. It's really fun to watch when the network is just a couple of hundred nodes.

Unfortunately.... even with 2000 nodes, the books aren't connected! Amazing. I don't know what to do... maybe work outward from suspected "connectors" like "Design Patterns," and "Design Patterns in C#" and "Design Patterns in Java." Anyway, my SpringEmbedderPanel doesn't zoom out, so it's impossible to generate a readable universe of connected books in a single image. Here are two images, one from early in the run with the complete network in play(with "C# Programming Language" on the left and "Java Programming Language" on the right), and another showing a portion of the display when the network is only around 200 books.

It's a fun program; I can't release it yet because it's all in C# 2.0 (with typesafe generics for which I'm very grateful!).

5:25:17 PM    comment []   trackback []

Bruce has an interesting discussion entitled “Generics Aren't”. It's primarily about the new support for generics in Java, but it has a lot of “generic generic” material as well.  via [Eric Gunnerson's C# Compendium]

The argument applies to C# generics, but dismisses type-safe data structures as only of concern to collections classes, but that's a narrow view. Using an interface loses type information (pace loose-typing discussion!). Consider the following, in which there's a desire not to allow Cats, Dogs, and Horses to interbreed :

interface BreedingAnimal
{
 BreedingAnimal Breed(BreedingAnimal spouse);
}

class Dog: BreedingAnimal
{
 public BreedingAnimal Breed(BreedingAnimal spouse)
 {
  return new Dog();
 }
}

class Cat: BreedingAnimal
{
 public BreedingAnimal Breed(BreedingAnimal spouse)
 {
  return new Cat();
 }
}

class Horse: BreedingAnimal
{
 public BreedingAnimal Breed(BreedingAnimal spouse)
 {
  return new Horse();
 }
}

class TypeSafeBreeder<T> where T:BreedingAnimal
{
 public T Reproduce(T aParent, T anotherParent)
 {
  return (T) aParent.Breed(anotherParent);
 }
}

class TypeSafeGenericsAreUseful
{
 public static void Main()
 {
  Dog lassie = new Dog();
  Dog rintintin = new Dog();
  Cat garfield = new Cat();
  
  TypeSafeBreeder<Dog> kennel = new TypeSafeBreeder<Dog>();
  Dog puppy = kennel.Reproduce(lassie, rintintin); //Isn't that nice?
  // Dog x = kennel.Reproduce(lassie, garfield);   //Won't compile. Isn't that nice?

  Horse flicker = (Horse) garfield.Breed(lassie); //<;- Compiles clean, runtime error. Darn you, type unsafe code!

 }
}

(exercise for the reader: as an interface BreedingAnimal.Breed is necessarily public, allowing access to the Breed() method without using a TypeSafeBreeder<T>. Change the design so that such a threat would only apply to classes in the assembly where these classes are defined.) 

11:39:46 AM    comment []   trackback []