Object Commando languages, development and design

19Mar/090

OCaml in the Real World

There's a great video of a talk given by Yaron Minsky on his blog that discusses why Jane Street chose to go with OCaml. It's definitely worth the time to watch. What's interesting about the decision was the casualness of it and the fact that it was based on merit and success. Often times at organizations the standard language is decreed. Yaron describes more of a decision based on track record. OCaml was used by Yaron for a research project there, it went well, so more people were brought in to work on it. It turned out it was easier to find good developers if you advertised for OCaml developers. I thought this was interesting, because it goes against what is a fairly commonly held belief in our industry.

Lower Cost for Reuse

One interesting point Yaron makes on the technical merits of OCaml was on reuse. He describes a very typical copy and paste problem in larger code bases. He talks about how this was much worse in object oriented languages than it was in OCaml. When pressed for more details he didn't have any hard proof but discussed higher order functions contributes to this. I agree with him on the less code duplication and cleaner code of OCaml. It's true that duplicate code is a sign that some refactoring needs to take place, but why doesn't it? We all know that duplicated code is bad. I think the reason this is worse in object oriented languages is because the barrier to entry is high on reuse. To have a small piece of reusable code, it must be put into a Class, if it's an instance method, you need to create an instance of it etc. If you have a few lines that are duplicated between two classes, what do you do?

  • Create a new class C (3 - 5 lines of code)
  • Create a method in C that wraps those few lines (3 lines of code)
  • Create an instance of that class in Class A (1 line of code)
  • Swap out the duplicate code for a call to the shared code (swap 3 lines for 1)
  • Create an instance of that class in Class B (1 line of code)
  • Swap out the duplicate code for a call to the shared code (swap 3 lines for 1)

Is this worth it? We just traded 3 lines of duplicate code for 10+. In the Java world this is still worth it, but it did take quite a bit of work to refactor those 3 lines. Coincidentally, we have just about the same amount of duplicate code as before (i.e. creating the instance of class C is the same, so is the method call). The benefit here is that the business logic isn't what is duplicated, it's the fluff code. So if the business logic is centralized, we have achieved quite a bit, but what about the duplication of the fluff code? In OCaml the steps would be

  • Create a new function (1 line)
  • Add those few common lines (3 lines)
  • Swap out the duplicate code in A for a call to the shared code (3 lines for 1)
  • Swap out the duplicate code in B for a call to the shared code (3 lines for 1)

The fluff in defining this shared code is minimal, because defining a function is minimal.